The aortic root is the anatomic segment between the left ventricle and the ascending aorta. Its function includes channeling large volumes of blood, maintaining laminar flow, and decreasing resistance and stress all under varying hemodynamic conditions and demands.[6],[9],[10],[11] Throughout the cardiac cycle, the aortic root is unfixed in both dimension and position.[1] This dynamic nature of root geometry includes serial expansion and contraction, forming a system that maximizes blood flow and reduces stress and strain on the aortic cusps, thus promoting their longevity.[1]

Functional Aortic Annulus

The general term “aortic annulus,” better described as the aortic root, refers to 3 major anatomic structures that include the (1) sinotubular junction (STJ), (2) ventriculoaortic junction, and (3) crown-shaped annulus comprised of the aortic leaflets, commissures, sinuses, and interleaflet triangles. When these 3 components are combined they are correctly referred to as the functional aortic annulus[9] (Figure 1). Aortic root terminology can often be confusing as the functional aortic annulus is not a true discrete fibrous annulus, but, rather, there is a transition zone where the ventricular muscle and cardiac fibrous skeleton change into aortic tissue[7] (Figure 2). In this area, approximately 45% of the annulus circumference is attached directly to the myocardium, with the remaining 55% attached to fibrous structures (Figure 2).

Figure 1

Functional Aortic Annulus. A) The functional aortic annulus includes the sinotubular junction, ventriculoaortic junction, and crown-shaped annulus comprised of the aortic leaflets, commissures, sinuses, and interleaflet triangles. B) Secondary view of the functional aortic annulus showing the coronary and anterior mitral leaflet attachments.

Figure 2

Subvalvular Aortic Anatomy and Annular Transition. The functional aortic annulus is not a true discrete fibrous annulus. Rather, there is a transition zone where the ventricular muscle and cardiac fibrous skeleton transition into aortic tissue. Areas of this transition include the subaortic curtain, muscular septum and membranous septum. Notably, approximately 45% of the annulus circumference is attached directly to the myocardium, with the remaining 55% attached to fibrous structures.

The STJ separates the aortic root from the ascending aorta and is located superior to the commissures.[6] Dilation of the STJ is the most common cause of central aortic insufficiency, and procedures replacing the ascending aorta with a short tubular graft, called remodeling, can restore valve competence (discussed later).[9]

The anatomical ventriculoaortic junction represents the border between the left ventricular myocardium and the arterial structure of the aorta.[6] Anatomic transition structures of this junction include the subaortic curtain and anterior mitral leaflet, muscular septum, and membranous septum (Figure 2). There has also been discussion of the hemodynamic ventriculoaortic junction as the separation level between ventricular and arterial hemodynamics.[6] Clarity should be used when distinguishing the 2 definitions as the hemodynamic ventriculoaortic junction also includes components of the crown-shaped annulus.

As the leaflet attachments insert into the wall of the aortic root, they form the crown-shaped fibrous structure or annulus. This structure encompasses the commissures, subcommissural triangles, and sinuses of Valsalva (Figure 1).

Leaflets/Cusps

The aortic valve contains 3 semilunar leaflets or cusps, anatomically divided into 3 parts: (1) the free margin; (2) the body of the leaflet; and (3) the basal components of leaflet attachments.[9] The leaflets are named by their anatomical position: right coronary leaflet, left coronary leaflet, and noncoronary leaflet. Each leaflet is suspended in a semicircular fashion, such that it is self-supporting in the closed position.[7] Competence of the aortic valve is obtained by coaptation of these self-supporting leaflets. Physiologically, the aortic valve leaflets form the hemodynamic ventriculoaortic junction between the left ventricle and the systemic circulation, where distally all areas are subject to arterial pressures, and proximally all areas are subject to ventricular hemodynamics.[9]

Commissures

The aortic commissures are defined as the distal parts of the leaflet attachments, although some nomenclature has extended this definition to include the peripheral area of the coapting parts of the free edges of the leaflets.[6] There are 3 commissures in total referred to by their anatomic placement between the coronary leaflets, including the right and left commissure, right and noncoronary commissure, and noncoronary and left commissure. Commussure misalignment has been shown to be associated with mild to moderate aortic regurgitation. [12]

Subcommissural Triangles

Three interleaflet triangles directly underlie each of the 3 commissures consisting of histologically thinned aortic wall and hemodynamic extensions of the left ventricular outflow tract extending to the STJ.[9] The triangle lying between the right-coronary and noncoronary sinuses faces the right atrium and is in direct continuity with the membranous septum proximally, which contains the bundle of His[9] (Figure 2). Injury to this area during aortic valve procedures may lead to temporary or permanent conduction issues, often requiring a permanent pacemaker.[9] The triangle underlying the left coronary and noncoronary sinuses contains the aorto-mitral curtain, extending to the anterior mitral valve leaflet. The subcommissural triangles of the noncoronary cusp are fibrous extensions of the intervalvular fibrous body and membranous septum, whereas the subcommissural triangle beneath the right and left coronary cusps is an extension of the muscular interventricular septum (Figure 2).

Sinuses of Valsalva

The Italian anatomist Antonio Valsalva was the first to name the 3 saccular outpouchings in the aortic wall, now known as the sinuses of Valsalva.[9] Two of the sinuses play host to the origin of the coronary arteries and are termed the left and right coronary sinuses. The third sinus is without a coronary artery attachment, and is hence termed the noncoronary sinus. The sinuses are limited proximally by the attachments of the valve leaflets and distally by the STJ. Although the precise function of the sinuses is unclear, evidence suggests the vortices created by the sinuses leads to stress reduction of the aortic leaflets and enhances coronary blood flow.[9],[13],[14],[15],[16] In valve-sparing aortic surgery, maintaining or recreating the sinuses recreates the vortices and may be beneficial for normal leaflet movement and valve durability. [9][17],[13],[14],[15],[16][18] However, aortic root reimplantation without recreating the aortic sinuses has not been shown to have deleterious effects on valve durability despite abnormal leaflet motion - and may provide increased radial commissural stability and leaflet coaptation.[19],[9],[15]

Valve Anomalies Including Bicuspid

The trileaflet aortic valve creates the optimal geometry for low resistance valve opening, whereas a bicuspid aortic valve (BAV) almost always demonstrates a degree of stenosis or dysfunction depending on the configuration.[9],[20] Previously, it is widely known that bicuspid valves generally occur in 3 forms based on the Sievers classification: type 0, those that are truly bicuspid with no raphe and no anterior rudimentary commissure; type 1, those with a median raphe and rudimentary commissure (most common); and type 2, those with a median and lateral raphe[20],[21],[22] (Figure 3).

Figure 3

Bicuspid Aortic Valves by Type. From Sievers and colleagues 2007 [16 ]. The left coronary sinus is on the left (surgeon’s view). The main category depends on the number of raphes. The first subcategory is determined by the spatial position of the cusps (type 0) and the raphes (types 1 and 2). The second subcategory is determined by the valvular function, characterized as follows: I, predominant insufficiency; S, predominant stenosis; B (I + S), balanced insufficiency and stenosis; No, normal function. The numbers represent the number of specimens from Sievers original analysis (percent in parenthesis).

True bicuspid valves (type 0) have 2 symmetric aortic sinuses, 2 commissures, and a symmetric base of leaflet implantation. These valves are more commonly associated with aberrant coronary anatomy compared with raphed bicuspids, with the most common coronary anomaly being rightward displacement of the right coronary juxtaposed with the commissure separating the right and noncoronary sinuses. This anomaly can make it difficult to create an appropriately sized coronary button for transfer without encroaching too close to the hinge point of the valve to allow for its reimplantation. In the absence of calcification, the most common cause of regurgitation in bicuspid valves is either elongation of one or both cusps due to root dilation with attendant cusp prolapse, or anterior cusp retraction due to tethering by the raphe and its rudimentary commissures, causing a lack of coaptation centrally.[1]

Type 1 BAVs are more prevalent, contain a median raphe on the conjoined cusp, and have an asymmetric distribution of the aortic sinuses. Typically, a large aortic sinus accompanying a large nonconjoined cusp and 2 smaller cusps fused together with a median raphe is observed. The raphe will often attach to the cusp base and form a pseudocommissure whose height is less than that of a true commissure. Raphes can be restrictive (typically fibrotic or calcified) and associated with small fused cusps in a triangular coaptation defect, or the raphes can be prolapsing, with well-developed cusps.

Type 2 BAVs, which are less prevalent than type 1 valves, have a median raphe as well as a lateral raphe. Their distribution of sinuses is also asymmetric and similar to the previously described type 1 aortic valves. Furthermore, quadricuspid and uniscuspid valves also exist, and their operative repair techniques are mentioned briefly later in this chapter.[23],[24],[25],[26],[27],[28],[29],[30],[31],[32],[23],[33],[34] Even machine-learning has been used to classify different types of bicuspid aortopathy.[35]

The morphology of BAV can vary greatly from perfectly symmetrical (Type 0) to very asymmetrical phenotypes.[36][37] As the commissure orientation and the length of cusp fusion decrease, the non-functional commissure height increases progressively (Figure 4). For example, a normal tricuspid aortic valve presents with a commissure angle of 120°. In a very asymmetric BAV, the commissure angle is increased to 130° while the fusion length increases and the commissural height decreases. At a commissure angle of 150°, this represents an asymmetric BAV. Finally, a symmetric BAV presents with a commissure angle of 180°. This new anatomical and repair-oriented classification system may aid to predict valve repair techniques.

Figure 4

New bicuspid aortic valve classification that illustrates the transition of a normal aortic valve through Type I to Type 0 bicuspid aortic valve.

Surgical Anatomy

Successfully repairing or completing aortic valve-sparing operations requires correcting the failing part of the aortic root and restoring the intra- and inter-component relationship of the aortic root elements to optimal dimensions and relations. Understanding the dynamics and core anatomical structure of the functional aortic annulus plays an important role in both aortic valve repair and the fitting and sizing of prosthetic valves. Ultimately, a surgeon’s understanding of annular geometry and dimensions will determine the long-term durability of their aortic root repair.[9],[38]

In an attempt to enhance the reproducibility of aortic valve-sparing reimplantation and annuloplasty, a recent study used 58 fresh aortic roots to analyze the topographic relationship between the ventriculoaortic junction, STJ, and basal ring of the crown-like annulus.[39] The study determined that although the internal aspect of the aortic root is relatively symmetric, the external aspect of the root is more asymmetric. This asymmetry is related to the 3-dimensional shape of the ventriculoaortic junction, which is 2.3 to 4.6 mm above the level of the basal ring from the left- and right-coronary commissure to the right- and noncoronary commissure. As a consequence, the external height of the noncoronary and left-coronary commissure is greater than the other 2 commissures. Furthermore, the root base thickness is variable along its circumference with an overall mean of 3.2 mm, but an increased mean of 6.2 mm at the muscular insertion. These findings should be taken into consideration when performing aortic valve-sparing reimplantation or annuloplasty.

Aortic regurgitation (AR) is the diastolic reflux of blood from the aorta into the left ventricle. It can result from leaflet deformation due to destruction, long-term remodeling, prolapse, or dilation of the annulus/STJ, thus preventing leaflet coaptation.[7]

Epidemiology and Etiology

The prevalence of AR increases with age and is found in less than 1% of individuals younger than 70 years years.[40] However, as a whole, AR is present in 13% of men and 8.5% of women.[41],[42],[43],[44] The causes of AR are extensive, but in general, they can be divided into those that affect the valve cusps and those that affect the aortic root. Valve cusps can be affected by calcific degeneration, congenitally bicuspid valves, infective endocarditis, rheumatic disease, myxomatous degeneration, and anorective medications such as fenfluramine and phentermine.[45],[46],[47]

The aortic root can be affected by dilation caused by aortic dissection, trauma, chronic systemic hypertension, aortitis (syphilis, viral syndromes, giant cell and Takayasu arteridities), connective tissues disorders (Marfan syndrome, Reiter disease, Ehlers-Danlos syndrome, osteogenesis imperfecta), and rheumatoid arthritis.[48],[49],[50],[51],[52]

Pathophysiology

The pathophysiology of AR is dependent on the acuity of onset and the duration for which the disease has been present. In acute AR, there is a sudden increase in the left ventricular-end diastolic volume. Because the left ventricle does not have time to remodel and its compliance is limited, the left ventricular end-diastolic pressure is rapidly elevated. Dramatic elevations in filling pressures may occur if the regurgitation is superimposed on a hypertrophic ventricle. Acute myocardial ischemia may result from increased afterload, compensatory tachycardia, a reduction in perfusion pressure as the left ventricular end-diastolic pressure approaches aortic diastolic pressure, and sudden death.

In chronic AR, the ventricle has time to remodel, resulting in dilation and eccentric hypertrophy secondary to the increase in left ventricular end-diastolic volume and wall stress. This dilation and hypertrophy causes an increase in stroke volume and helps maintain forward blood flow, creating a wide pulse pressure seen on examination.[53] Most patients remain asymptomatic for decades, even with severe regurgitation, because recruitment of preload reserve and compensatory hypertrophy maintain a normal ejection fraction despite increased afterload. However, with time, the heart can no longer hypertrophy, the left-ventricular ejection fraction drops, and heart failure ensues.[54],[55] The patient becomes symptomatic with dyspnea and angina secondary to impairment of coronary flow reserve.

Clinical Characteristics

The symptoms of aortic insufficiency are dependent on the acuity of presentation. Acute AR can be life-threatening because the ventricle has not had sufficient time to remodel. Patients will often present with ischemic symptoms due to decreasing coronary perfusion and increased myocardial oxygen demand. In comparison, chronic AR has a slow and insidious onset, allowing patients to be asymptomatic as compensatory left ventricular changes occur. However, once the ventricular changes are maximized, heart failure symptoms will be present, including angina, exertional dyspnea, exertional syncope, orthopnea, paroxysmal nocturnal dyspnea, and palpitations.

Pertinent physical examination findings include an early diastolic blowing decrescendo murmur, widened pulse pressure with water-hammer pulse, head bobbing with heart beats (de Musset sign), pulsations of the lip and fingers (Quincke pulse), pistol shot sounds over the femoral artery (Traube sign), and pulsation of the uvula (Muller sign). The diastolic blowing murmur is best heard near the level of the diaphragm at the left sternal border while the patient is sitting, leaning forward, and deeply exhaled.

Diagnosis

Two-dimensional transthoracic echocardiography with Doppler color flow is the standard tool for the diagnosis of aortic insufficiency.[56],[57],[58] Important components of evaluation include jet width, vena contracta width, regurgitant volume, regurgitant fraction, and regurgitant orifice. Assessment of the severity of aortic insufficiency is determined qualitatively by jet width and vena contracta width, and quantitatively by regurgitant volume, regurgitant fraction, and regurgitant orifice area, where the regurgitant orifice is calculated by dividing the regurgitant volume by the velocity time integral of the aortic insufficiency jet calculated by continuous wave Doppler.[59] Using these echocardiographic findings, the classification of aortic insufficiency severity can be broken into 3 primary categories: mild, moderate, or severe (Table 1).

Aortic root aortography at the time of left heart catheterization may also help delineate the degree of regurgitation. The amount of regurgitant flow can be calculated by angiographic stroke volume minus a measured fixed stroke volume. The difference between these 2 measured volumes divided by the angiographic stroke volume determines the regurgitant fraction. In this method, ejection fraction is estimated roughly.

Electrocardiography (ECG) can also be used as a diagnostic tool. The increased left ventricular mass in chronic aortic insufficiency leads to left axis deviation and increased QRS complex magnitude. A strain pattern and reduction in the total QRS complex amplitude in patients with chronic severe aortic insufficiency is highly predictive of severe depression of ejection fraction resulting from inadequate hypertrophy.[60] Q waves in leads I, V1, and V3 through V6 are indicative of diastolic volume overload.[61] Left ventricle conduction defects occur late in the course and are usually associated with left ventricular dysfunction. However, overall ECG is an inaccurate predictor of aortic insufficiency severity.

Indications and Timing for Surgery

Aortic valve repair indications

The indications specific to aortic valve repair have not been standardized, but have been based on the established indications for general aortic valve intervention and replacement, including congestive symptoms of exercise intolerance, asymptomatic patients with left ventricular dysfunction, and asymptomatic patients with left ventricular dilation and/or a significant reduction in myocardial contractility[62],[63],[64] (Table 2). Once these baseline aortic intervention criteria have been satisfied, judgment about a patient’s candidacy for aortic valve repair vs replacement should be based primarily on the quality and character of the aortic cusps, the surgeon’s experience, and the patient’s understanding of the inherent risks of reoperation.[1] When considering aortic valve replacement vs repair, 1 clinical review determined the indications for aortic valve repair to be (1) pure annular dilation without significant degeneration of the leaflets themselves, (2) single leaflet prolapse with normal mobility and excursion of the leaflets by echocardiography, (3) mild stenosis with aortic insufficiency due to 1 of the above causes without significant calcification or leaflet destruction, or (4) a small leaflet perforation amenable to simple suture repair.[7] Preservation of the native aortic valve via the valve sparing-aortic root replacement procedure, as discussed later in this chapter, may be possible at high volume aortic centers in selected patients with favorable valve anatomy who are undergoing surgical replacement of the aortic sinuses and/or ascending aorta.[65][66][67][68][69][70]

Although more data are to come on the specific indications for aortic valve repair, for the time being, surgeons can safely rely on the recommendations from the American College of Cardiology and the American Heart Association for overall aortic valve intervention.[71],[63],[72][73] These recommendations are stratified by classes I, IIa, and IIb (Table 2).

The class I recommendations for aortic valve intervention in patients with AR include (1) symptomatic patients with chronic severe AR, (2) asymptomatic patients with chronic severe AR and left ventricular dysfunction (ejection fraction ≤ 55%) at rest, and (3) asymptomatic patients with chronic severe AR who are undergoing concomitant coronary artery bypass grafting, aortic surgery, or other heart valve surgery.[63]

The class IIa recommendation for intervention is for (1) patients with asymptomatic, severe AR and normal left ventricular systolic function (ejection fraction > 55%) but with left ventricular dilation (end-systolic diameter > 50 mm or 25 mm/m2) and (2) patients with moderate AR who are undergoing concomitant coronary artery bypass grafting, aortic surgery, or other heart valve surgery.

The class IIb recommendation is for low surgical risk patients with severe AR who have progressive decrease in left ventricular function (EF < 55% - 60%) or increase in left ventricular dimension with LVEDD >65 mm on at least 3 studies.

Additionally, individuals with aortic root or ascending aorta pathology will have varying degrees of associated aortic valvular disease leading to repair. Endocarditis with hemodynamic compromise, persistent bacteremia, sepsis, conduction abnormalities, recurrent embolization from vegetations, or annular abscess formation should necessitate urgent surgical intervention.

Aortic root replacement indications

Overall, aortic valve repair in conjunction with aortic root replacement is feasible in appropriately aged patients.[1] Aortic root replacement is indicated when the predicted annual risk of an aortic catastrophe (dissection, rupture, or sudden death) or heart failure due to associated aortic insufficiency (in the setting of a dilated root) significantly exceeds the risk of surgical reconstruction.[74],[75],[76],[77] This risk is dependent on the diameter of the aneurysm and the associated genetic abnormality. Thus correct measurement of the diameter of the aortic sinuses and ascending aorta is essential for perioperative management. BAVs are often the exception to this rule, as aortic insufficiency may ensue before the diameter of the aneurysm reaches a threshold where the risk of rupture and dissection outweigh the risk of surgery.[78],[79],[24]

The most common aortic aneurysm size for intervention is between 4.2 cm and 5.5 cm in diameter, depending on the aneurysmal type and genetic predisposition[80],[81],[71],[82],[83],[84],[85](Table 3). Specifically, for patients with Loeys-Dietz syndrome, the surgical threshold for aortic root and ascending aortic replacement should be informed by the specific genetic variant, family history, and aortic diameter and growth rate (Table 4). Please note, in the setting of other concomitant cardiac surgeries or in surgeries with different types of biscupid aortic valves, the indications for repair based on the diameter of the aortic root often occur with smaller root diameters. For example, a BAV aortopathy of 55 mm in diameter or greater should undergo surgical intervention based on class I recommendation. When the diameter is between 50 – 54 mm with additional risk factors for aortic dissection; or when the diameter is greater than 45 mm with concomitant need for aortic valve repair or replacement, surgical replacement of the aortic root or ascending aorta is indicated if performed by experienced surgeons in a multidisciplinary aortic team based on class IIa recommendation. If the cross-sectional aortic root or ascending aortic area (cm2) to height (m) ratio is at least 10 cm2/m, surgical repair is also reasonable per class IIa recommendation. Lastly, in patients with BAV, a diameter of the aortic root or ascending aorta of 50 – 54 mm with no other risk factors for aortic dissection and at low surgical risk, surgical intervention may be reasonable when performed by experienced surgeons in a multidisciplinary aortic team based on class IIb recommendation. Risk factors for aortic dissection include family history of aortic dissection, aortic growth rate of at least 3 mm/year, aortic coarctation, and “root phenotype” aortopahy. The numbers listed in the table should serve as a basic guideline only.

For patients with a family history of aortic dissection, surgery should be considered before the aneurysm reaches the common size for intervention. The growth rates of ascending aortic aneurysms are often exponential, ranging from 0.8 mm/year for small aneurysms (< 4 cm) to 16 mm/year for large aneurysms (8 cm).[75] The growth rates for aortic root aneurysms can be higher and more variable depending on the genetic syndrome.[86],[87],[88],[89] Standard practice is to surgically intervene if the growth rate is greater than 5 mm/year. . Moreover, growth of 3 mm/year or more still substantially exceeds the expected growth rate for aneurysms of the root and ascending aorta. If this rate of growth is sustained for 2 consecutive years, intervention is also recommended. [83][85]

High risk features include women with TGFBR2 and small body size; severe extra-aortic features, such as craniosynostosis, cleft palate, hypertelorism, bifid uvula, marked arterial tortuosity, widened scars, and translucent skin; family history of aortic dissection, especially at young age or relatively small aortic diameter; and aortic growth rate > 3 mm/year. * Family history, age, and aortic growth rate also inform surgical thresholds.

Similar to aortic valve replacement vs repair, if valve-sparing aortic root replacement with or without valve repair cannot be performed with as low an operative risk as conventional root replacement, then it should probably not be considered.[1] Currently guidelines by Gleason include indications based on heritable risk factors, maximal orthogonal diameter of the aortic root, age, and degree of aortic insufficiency.[1] Valve-sparing root replacement is considered in all patients younger than 70 years who have a life expectancy greater than 15 years, when many bioprosthetic valves will fail. Furthermore, valve-sparing root replacement and valve repair should be considered in patients with a root aneurysm or dissection and a suitable aortic valve if they have a contraindication to anticoagulation and they understand the risks of potential need for reoperation.

A few basic considerations exist when deciding between the reimplantation technique and the remodeling technique. The reimplantation technique is an ideal operation for young adults with aortic root aneurysms associated with genetic syndromes. In those patients with genetic syndromes the remodeling technique should not be used as the need for repeat surgical intervention is much higher than with the reimplantation technique. The remodeling technique is an ideal operation for older patients with an ascending aortic aneurysm and aortic insufficiency secondary to a dilated STJ and a normal aortic annulus.[80] In these patients the remodeling technique is simpler, and both procedures are likely to be equally as effective.

Natural History and Consideration of Earlier Repair

Without surgical intervention, the estimated mortality rate for patients with AR is greater than 10% per year for patients with angina and greater than 20% per year for patients with congestive heart failure symptoms. In asymptomatic patients with normal left ventricular systolic function, the rate of progression to symptoms or left ventricular dysfunction is 4% per year. However, asymptomatic patients should be closely observed as approximately 25% of patients may develop left ventricular dysfunction or die before becoming symptomatic.[90]

Similar to mitral valve repair for mitral regurgitation, there is some suggestion that aortic valve intervention should be considered earlier in patients in whom aortic valve repair is likely.[91],[92] Sharma and colleagues evaluated 331 patients who underwent elective aortic valve repair from June 1986 to June 2011. Repair methods included commissuroplasty, triangular resection, plication, resuspension/cusp shortening, and perforation closure. In-hospital mortality was 0.6% (2 of 332). Four patients (1%) experienced early repair failure with 2 patients undergoing repeat repair. Overall survival was 91% and 81% at 5 and 10 years, respectively. The authors found that greater left ventricular end-systolic dimension (>50 mm) and lower ejection fraction (< 50%) were significant predictors of long-term mortality and that awaiting the onset of ventricular dysfunction increases the risk of late mortality, thus warranting earlier consideration of aortic valve repair in patients with suitable anatomy.

Classification

A classification system of aortic valve insufficiency has been developed [93],[94] (Figure 5) and focuses on the concept that the aortic valve consists of 2 major components: the aortic annulus and the valve leaflets.

Figure 5

Classification of Aortic Insufficiency with Associated Repair Technique. From Boodhwani and colleagues. 2009 [73 ]. FAA = functional aortic annulus; SCA = subcommissural annuloplasty; STJ = sinotubular junction.

Type 1 aortic insufficiency is associated with normal leaflet motion and is broken down into subtypes a, b, c, and d. Type 1a aortic insufficiency is secondary to STJ enlargement and dilation of the ascending aorta. Type 1b aortic insufficiency is secondary to dilation of the sinuses of Valsalva and the STJ. Type 1c aortic insufficiency is secondary to dilation of the ventriculoaortic junction. Type 1d aortic insufficiency is secondary to cusp perforation without a primary functional aortic annulus lesion. In types 1a, 1b, and 1c, a centric jet is expected. However, for type 1d an eccentric jet is expected.

Type II aortic insufficiency is secondary to leaflet prolapse due to excessive cusp tissue or commissural disruption. Type III aortic insufficiency is secondary to leaflet restriction, which is often seen in cases of calcification, thickening, and fibrosis of the leaflets such as bicuspid, degenerative, or rheumatic valvular disease.

A thorough understanding of the classification of AR allows for the generalized dissemination of repair techniques and a common language for communicating between specialties. Patients with type 1a insufficiency secondary to dilation of the STJ and ascending aorta are good candidates for sinotubular remodeling including an ascending aortic graft, as well as possible subcommissural annuloplasty. Patients with type 1b insufficiency secondary to dilation of the sinuses of Valsalva are good candidates for aortic valve-sparing procedures, including reimplantation or remodeling. Patients with type 1c aortic insufficiency secondary to ventriculoartic junction dilation are good candidates for subcommissural annuloplasty and STJ annuloplasty. Patients with type 1d aortic insufficiency secondary to cusp perforation may be treated with an autologous or bovine pericardium patch. Type II regurgitation secondary to cusp prolapse is amenable to several repair techniques, including free margin plication, triangular resection, and free margin resuspension. Type III regurgitation secondary to cusp restriction is amenable to repair by shaving, decalcification, and patch techniques.

It is important to remember that patients can exhibit multiple lesions that contribute to their aortic insufficiency and may not fit into a single classification.

Preoperative Considerations

For AR, systemic hypertension should be controlled with vasodilators to increase forward blood flow and reduce the degree of AR. However, excessive afterload reduction can reduce diastolic coronary perfusion pressure and exacerbate ischemia. Beta-Blockers typically used for control of ischemia must also be used with caution as slowing the heart rate may increase the amount of regurgitation. If the AR is acute, β-Blockers should be avoided entirely as they will block the compensatory tachycardia. Placement of an intra-aortic balloon pump is contraindicated for control of angina symptoms as it will causes worsening regurgitation and left ventricular dysfunction. In the rare case that after completing an aortotomy the valve cannot be repaired or spared, preoperative dental work should have been completed in anticipation of valve placement.

Anesthesia and Monitoring

Anesthetic management should be tailored to each individual by taking into consideration the patient’s age, comorbidities, coronary and valvular disease, left ventricular dysfunction, and plans for early extubation. In the setting of AR, the hemodynamic goals in the pre-bypass period are to maintain satisfactory preload while avoiding bradycardia and hypertension. Vasodilators can be beneficial but should be used with caution as they can cause hypotension, reduce diastolic perfusion pressure, and precipitate ischemia.[90]

For those patients with AS, the left ventricle is typically stiff, with some degree of diastolic dysfunction, and the induction of anesthesia is a critical period for patients. Avoidance of causes that lower the cardiac output, such as hypovolemia, myocardial depression, vasodilation, tachycardia, or dysrhythmias, should be avoided. Alpha-agonistic agents can be extremely helpful in supporting systemic resistance during induction. If atrial fibrillation occurs before the initiation of bypass, cardioversion may be necessary if profound hypotension is present. Use of a Swan-Ganz catheter and arterial blood pressure line is important to optimize perioperative hemodynamics.[90]

Surgical Approaches and Exposure

Aortic valve repair procedures are typically completed through a median sternotomy. Arterial cannulation is performed distal to diseased segments of the aorta, which is typically in the distal ascending aorta. However, if aortic arch pathology is present, axillary artery cannulation may be performed. In most cases, 2-stage venous cannulation is done through the right atrial appendage, and cardioplegia is retrograde. Following the administration of cardioplegia, an aortotomy is made approximately 1 cm above the STJ, starting above the noncoronary sinus. The aortotomy is then extended circumferentially.

Alignment Examination

After completion of the aortotomy, and in order to create a dynamic assessment of the valve anatomy, 3 full-thickness traction sutures are placed at the 3 commissures, and retracted using clamps. The distal aorta is retracted cephalad, and axial traction is applied on the commissural traction sutures. This technique illustrates the physiologic aortic valve closure position, allowing the surgeon to assess the area and height of coaptation. Leaflets can be inspected to assess mobility, restriction, calcification, and prolapse.

Technical Considerations for Repair and Root Replacement

Successful valve preservation requires thorough interrogation of the aortic root and valve with transesophageal echocardiography and then direct visual inspection. Typically the best transesophageal echocardiography views for aortic valve surgery are obtained in the midesophageal short- and long-axis views. The transgastric long-axis view with Doppler can also be used for assessing regurgitation. When both valve-sparing root replacement and aortic valve repair are combined, some surgeons have found it helpful to complete the root and annular dissection with excision of the sinus segments before repairing the aortic valve, as this approach allows optimal mobility and visualization of the cusps, annulus, and commissures to facilitate the reconstruction.[1]

Important components to characterize include (1) the number, mobility, and thickness (sclerosis/fibrosis) of the cusps, (2) the degree of annular and cusp calcification, (3) the presence or absence of a median raphe in bicuspids, (4) the presence of cusp prolapse, (5) fusion, (6) fenestrations or tears, and (7) the direction and extent of regurgitation.[1] Calcifications often preclude a durable repair and should prompt consideration of valve replacement. Mild cusp thickening (sclerosis or fibrosis) is often acceptable provided there is adequate mobility and pliability of the cusps. However, cusp thickening has been shown to limit the durability of the valve.[22],[95] Depending on the depth and length of the cusps, fenestrations near the commissures may be repairable with leading edge reinforcement. However extensive fenestrations are typically associated with elongated cusps that lead to persistent post-repair cusp prolapse and potential eccentric regurgitation. Aortic valve endocarditis requiring surgery often requires extensive debridement of the valve and root beyond what is amenable to aortic valve repair. However, isolated tears may be amenable to resection and cusp augmentation with a pericardial patch.[96],[97]

After confirmation of the adequacy of the cusps, several measurements should be obtained to help direct a repair, including (1) cusp depth, (2) cusp length – leading edge, (3) commissural height, and (4) diameters of the annulus, sinus segment, and STJ.[1] As a reminder, diameters of the annulus and ventriculoaortic junction can be estimated by echocardiography but should be confirmed by using valve sizers or calibrated dilators. Cusp measurements and commissural heights are best measured directly.[1]

Attention to root geometry is very important to having a successful repair. Many roots have asymmetric sinus segments, particularly in patients with a BAV or those with annuloaortic ectasia or Marfan syndrome.[24],[25] The noncoronary sinus can be significantly larger than the right or left sinus, and discrepancies in relative size need to be factored into root repair. Neosinus creation that is too small can cause post-repair cusp prolapse.[1],[98],[99],[100]

From a physiologic perspective, remodeling of the aortic root has traditionally been deemed superior to reimplantation of the aortic valve because the remodeling procedure allows for the preservation of the aortic annulus movements during the cardiac cycle.[15] However, from a functional long-term perspective, results of valve sparing aortic root replacement have been much better in patients undergoing the reimplantation procedure, particularly in patients with aortic root aneurysms associated with genetic syndromes and BAVs who are prone to dilation of the aortoventricular junction.[101],[102],[103],[104],[105],[69],[106] For these reasons, remodeling of the aortic root is an excellent operation in older patients with ascending aortic aneurysm, secondarily dilated aortic sinuses, and a normal atrioventricular junction. In this subgroup of patients, remodeling is not likely to fail because the aortic annulus will not dilate after surgery.[80]

After repair completion, intraoperative echocardiography should always be completed to assess valve anatomy and the mechanism of valve dysfunction. If more than trivial to mild residual aortic insufficiency is present, coaptation height is below the aortic annulus, and coaptation length is less than 5 mm, then aortic valve reexploration should occur to minimize predictors of late repair failure.[107],[108]

Angioscopy has also been reported as a means of obtaining a complete intraoperative evaluation of valve geometry.[109] In this technique a flexile autoclavable videoscope (length of 60 cm, diameter of 5 mm, Olympus) is used.[110] Following repair of the aortic valve and the replacement of the ascending aorta, the angioscope is placed within the lumen of the vascular graft parallel to a cannula for administration of approximately 500 mL cold crystalloid. The solution is administered using a pressure cuff, and the left ventricle is simultaneously vented. Pressure in the aortic root of at least 60 mm Hg is established. The symmetry of the aortic leaflets’ coaptation is then evaluated under physiologic conditions and, reportedly, leakage can be identified in less than 2 minutes. In patients with symmetric leaflet coaptation on angiography, no residual regurgitation was observed on postoperative echocardiography. Minimal central leakage with symmetric leaflet coaptation on angiography resulted in mild regurgitation on echocardiography. Asymmetric leaflet coaptation without or with leakage demonstrated mild to moderate residual regurgitation. Although traditional testing of the aortic valve after repair is done using a flush maneuver, angiography adds the benefit of visualization of the repair during diastole and does not require extensive experience to master.

Though intraoperative echocardiography remains the primary mode of aortic valve repair assessment, the results are highly operator dependent and do not allow for direct visualization of the valve. Recently, a new device has been developed.[111] This transparent device is in a conical form and is secured to the distal aorta or graft above the aortic valve to create a secure, water-tight, pressure-resistant seal. The device also has one port for fluid infusion into the device while another port allowing air removal. Once de-airing is complete, the de-air port is closed for further pressurization of the aortic root. The distal surface allows for a bigger visualization field. At physiologic diastolic pressure, surgeons can clearly visualize aortic valve morphology and assess any anomalies that require further repair. The use of this device does not require synthetic grafts, autoclavable videoscope, or any cumbersome setup. This stand-alone device (Figure 6) may help increase the adoption of aortic valve repair by providing a better tool for intraoperative visual assessment of the aortic valve.

Figure 6

The intraoperative use of the aortic valve visualization device in a patient undergoing valve-sparing aortic root replacement. Note the additional aortic cusp repair sutures used via the free margin plication technique guided by the aortic valve morphology and cusp prolapse visualized using the device under physiologic diastolic pressure. The aortic valve was successfully repaired with proper coaptation plane re-established.

Learning Curve

The surgical learning curve for aortic valve repair can be very steep and unforgiving. However, if the aortic valve leaflets are not pathologically damaged, the vast majority of these valves can be preserved.[8] Past relative contraindications such as a very large aortic annulus, severe AR, or eccentric AR due to cusp prolapse have been overcome with new surgical techniques.[8] In a recent study analyzing the learning curve for aortic valve repair, the authors concluded that initiation of dedicated programs improved procedural safety, efficacy, and consistency with an overall learning curve of 40 to 60 cases.[112] Two separate cohorts were analyzed and divided into 3 equal tertiles. Early mortality was less than 1%, and a significant reduction in the incidence of safety events (mortality, myocardial infarction, stroke, early aortic valve repeat surgery, reexploration for bleeding, or pacemaker implantation) occurred over the tertiles (18%-20%, 12%-15%, and 3%-8% as case experience accumulated by tertile, respectively). Aortic cross-clamp and cardiopulmonary bypass times decreased significantly after the second tertile in cohort A and the first tertile in cohort B. Most safety events centered on the need for pacemaker insertion and reopening for bleeding rather than myocardial infarction, cerebrovascular accident, or mortality, and although the overall number of permanent pacemaker insertions was low, this complication was not unexpected given the proximity of the conduction system to local manipulation at the repair boundaries.

Special Considerations in Postoperative Care

Any aortic valve procedure may be complicated by heart block secondary to edema, hemorrhage, suturing, or debridement near the conduction system that lies near the base of the right coronary cusp and noncoronary cusp. It is more likely to occur in patients with preoperative conduction system disease, AR, or following operations requiring extensive resection such as endocarditis. Epicardial atrioventricular pacing wires may be necessary for several days postoperatively and should routinely be placed in the operating room. The presence of a bundle-branch block following aortic valve replacement has been shown to be an adverse prognostic indicator, which should be kept in mind for aortic valve repair.[113] If complete heart block persists for more than a few days, that is, enough time for edema and hemorrhage to dissipate, placement of a permanent pacemaker should be considered.

Attempts at aortic valve repair began in the late 1950s before and soon after the availability of cardiopulmonary bypass with techniques like circumclusion, bicuspidization, aortic and annular plication, and annuloplasty.[1],[114],[115],[116],[117],[118],[119] These techniques were not very successful at the time, and with the development of valve prostheses, aortic valve repair was moderately abandoned. Fortunately, Carpentier’s innovations of mitral valve repair techniques in the 1970s and 1980s created new interest in aortic valve repair using techniques such as annuloplasty, midleaflet excisions for prolapse, commissurotomy, and leaflet shaving for restricted cusps.[93] Pericardial leaflet extension, pericardial monopatch, leaflet unfolding, supra-aortic crest enhancement, cusp resuspension, and cusp plication were all further developed during this time.[120],[121],[122],[123]

Various methods of aortic valve repair exist[124] and, depending on the author, varying terms have been used to describe several repair techniques. The reader of this text should keep in mind that diverse pathology exists and commonly more than 1 technique is required to repair the valve in any given patient.

Annuloplasty: Aortic Root and Annulus Remodeling

When patients with aortic insufficiency secondary to aortic root dilation without structural valve defects are identified, several possible repair techniques exist before it is necessary to perform a valve-sparing aortic root replacement. These techniques include circular annuloplasty, commissural and subcommissural annuloplasty, and external aortic annuloplasty.

Circular annuloplasty, also known as circular suture, is a continuous mattress suture, typically of 2-0 nonabsorbable suture, that is passed through the aortic wall at the attachment point of the leaflet caudad toward the ventricle and then cephalad from the ventricular side back up through tissue at the leaflet attachment point. The mattress suture is brought around the entire circumference of the valve (Figure 7). The suture is pulled tight at the ends to imbricate the wall of the aorta, decrease the circumference, and bring the leaflets to better coaptation. This suture is not at what might be defined as the annular level, but it traces the attachment point of the valve leaflets.[7]

Figure 7

Circular Annuloplasty. A continuous mattress suture is passed through the aortic wall at the attachment point of the leaflets circumferentially. The suture is pulled tight at the ends to imbricate the wall of the aorta and decrease the circumference.

Commissural or subcommissural annuloplasty are similar to circular annuloplasty and can both be used to treat annular dilatation. The only major difference in their techniques is the level at which the sutures are placed. In commissural annuloplasty the sutures are placed at the commissural level and not the annular or subannular level. The aortic wall is plicated at each commissure with a separate pledgeted, horizontal mattress stitch, resulting in reduced aortic circumference. The pledgets can be secured within the aorta or externalized outside the aorta.[1] Benefits of this procedure include easy learning curve and minimal added operative time.[7] This procedure can be performed alone or in combination with a circular annuloplasty, which has been described for pulmonary autograft transfer (Ross procedure) and the remodeling technique of valve-sparing root replacement.[125],[126],[127],[128],[129],[130],[131] By using a running reinforcement suture, annular dimensions can also be reduced.[132]

Subcommissural annuloplasty is further used to reduce the width of the interleaflet triangle, improve cusp coaptation, and help stabilize the ventriculoaortic junction (Figure 8). It is typically completed at the midcommissural level, except at the noncoronary and right-coronary commissure where it should be completed higher to avoid the membranous septum and conduction tissue. At the other 2 commissures, the surgeon can perform the annuloplasty at a lower level to create a greater increase in coaptation if desired. The first arm of suture is passed from the aortic to the ventricular side within the interleaflet triangle and then brought back out the aortic side at the same level. The second arm of the suture is passed in the same fashion just below the first and a pledget is added. Care should be taken during suture tying not to tear the septum.

Figure 8

Subcommissural Annuloplasty. The first arm of suture is passed from the aortic to the ventricular side within the interleaflet triangle and then brought back out the aortic side at the same level. The second arm of the suture is passed in the same fashion and a pledget is added.

External annuloplasty using a flexible ring is the most frequently used option to correct ventriculoaortic junction dilation aside from valve-sparing root replacement.[126] It can be used as an adjunct to valve-sparing root replacement (Lansac Hybrid) or in isolation (Figure 9). The procedure has been limited by the ability to place an external ring at the level of the true ventriculoaortic junction because external dissection is limited. However, several systems are being developed including PEARS (personalized external aortic root support).[133],[134],[135],[136] For this procedure a custom-made macroporous mesh is manufactured based on the patient’s aortic root, ascending aorta size, and overall shape per computed tomography, and secured around the aortic root.[137],[138],[139] However, data are currently limited on these outcomes, and more work is to be completed.[140] A video showing geometric ring annuloplasty for aortic valve repair can be found here:

Figure 9

External Aortic Annuloplasty. A flexible ring is sutured into place at the ventriculoaortic junction. The ring can be used as an adjunct to valve-sparing root replacement (Lansac Hybrid) or in isolation.

Cusp Repair Techniques by Pathophysiology

Aortic valve repair techniques can be classified by the pathophysiology of the anatomic components they seek to address.

Prolapse Elongation

Cusp prolapse is often isolated to 1 cusp and creates eccentric AR. It is the most frequently encountered lesion and is associated with excess length of the free margin. Evaluation of the valve will show the leading edge of 1 cusp is significantly longer than the other(s).[1] The 2 nonprolapsing cusps are used as a reference to estimate the required reduction in the free margin length. This defect can be addressed by triangular resection, free margin plication, or free margin resuspension.

Triangular resection involves excising a triangle of tissue in the middle of the prolapsing valve and then suturing the edges back together to decrease the transverse length, which brings all of the leaflets together.[7] (Figure 10) A continuous suture is recommended instead of interrupted sutures because it decreases the chance of a leak and lessens the thrombogenic “knot-burden.”[7] This method is more commonly used for bicuspid valves to excise the median raphe; the anterior cusp of a bicuspid valve is often redundant, prolapsing, and has a prominent, thickened raphe that is ideally suited to triangular resection. However, it is also beneficial with tricuspid valves if 1 leaflet is redundant and prolapsing. The extent of resection is based on measurements of the leading edges of the 2 leaflets. Provided the posterior cusp is not prolapsing, its leading edge length should be the length of reference.[1] Any separation of the cusps after triangular resection can be addressed with additional commissuroplasty or with commissural plication. Triangular resections should not extend across the entire depth of the cusp to the hinge point but should involve approximately one-half to two-thirds of the cusp depth. Typically a running 6-0 to 7-0 polypropylene suture is used for the reapproximation.[1] Knots should be tied on the aortic side of the cusp and not at the leading edge. Triangular resections can also be useful near the commissural aspects of the leading edge when the prolapsed segment of a cusp is eccentrically located and the cusps are thick enough to suture without tearing.

Figure 10

Triangular Resection. A triangle of tissue is excised from the middle of the prolapsing valve and the edges are sutured back together to decrease the transverse length.

Free margin plication can be done both centrally and at the commissures (Figure 11). Central plication is effective when the noduli are not particularly prominent or thickened.[141],[142] It is most useful when there is only a small discrepancy in the lengths of the leaflets (2 to 5 mm).[1] Typically a 7-0 polypropylene suture is passed through the center of the 2 nonprolapsing reference cusps, and gentle axial traction is applied. The prolapsing cusp is gently pulled parallel to the reference cusp, and a 6-0 polypropylene suture is passed through the prolapsing cusp, from the aortic to ventricular side, at the point at which it meets the center of the reference cusp. The direction of traction on the prolapsing cusp is then reversed and the same suture is passed from the ventricular to the aortic side of the cusp where it again meets the center of the reference cusp. The margin is then plicated by tying this suture with the excess tissue on the aortic side. The plication can be extended 5 to 10 mm onto the body of the aortic cusp by adding additional interrupted sutures or running locked sutures. Significant excess tissue can be shaved off using a scalpel or scissors as long as sufficient tissue is present to bring the edges together.

Figure 11

Free Margin Plication. A suture is passed through the center of the 2 non-prolapsing reference cusps and gentle axial traction is applied. The prolapsing cusp is gently pulled parallel to the reference cusp and a second suture is passed from the aortic to ventricular side at the point at which it meets the center of the reference cusp (A). The direction of cusp traction is reversed and the same suture is passed from the ventricular side to the aortic side (B). These steps can be repeated to run the suture towards the leaflet attachment (C). The margin is then plicated by tying this suture (D).

Commissural cusp plication can be applied at one or both ends of the leading edge of a cusp using the same methods as above for central free margin plication. Compared with central plication, commissural plication can accommodate a larger discrepancy in cusp lengths. This technique is particularly useful in bicuspid valves, serving to both close a commissural gap and shorten the leading edge of 1 leaflet.[1] Commissural cusp plication is not appropriate when there are large stress fenestrations near the commissure. Secure plication sutures in any location along the leading edge are dependent on valve integrity strong enough to hold sutures. If a cusp is too thin or flimsy at the leading edge, it is not a good candidate for plication.[1] Plication of the free edge margin is an alternative to shorten the free edge of the leaflet with a continuous running suture, commonly referred to as free edge leaflet plication.[7]

Free margin resuspension is performed by identifying the prolapsed leaflet-free edge and then plicating this free margin to the aortic wall to remove valve redundancy [143],[144] (Figure 12). This procedure returns the coaptive surfaces to the same level, correcting misalignment and reestablishing competency.[7] It is particularly useful in the setting of a fragile free margin with multiple fenestrations or to homogenize the free margin when a pericardial patch is used for cusp augmentation.

Figure 12

Free Margin Resuspension. A suture is first passed through the center of the 2 nonprolapsing cusps to create a stable reference. A second suture is passed twice at 1 end of the commissure an. One arm of the suture is passed over the length of the free margin in a running fashion and locked at the other commissure (A). A second suture is then passed in the same fashion along the cusp free margin. The length of the free margin can then be reduced by applying gentle traction on each branch of the suture and tying at the commissures (B).

A 7-0 polypropylene suture is first passed through the center of the 2 nonprolapsing cusps to create a stable reference. A 7-0 suture is then passed twice at 1 end of the commissure. One arm of the suture is passed over the length of the free margin in a running fashion and locked at the other commissure. A second 7-0 suture is then passed in the same fashion along the cusp-free margin. The length of the free margin can then be reduced by applying gentle traction on each branch of the sutures and applying opposite resistance with a forcep at the middle of the free margin. The sutures should be reduced until the free margin reaches the same length as the reference cusps’ free margin. This same maneuver is applied to the second half of the free margin. By doing the procedure in 2 steps the surgeon is able to complete symmetric and homogenous shortening. When the desired amount of free margin shortening is achieved, the 2 suture ends are tied at each commissure.

Pure annular dilation

Annular dilatation is often 1 of the mechanisms invoking AR in the setting of an aortic root aneurysm and can be addressed by circular annuloplasty, subcommissural annuloplasty, or external annuloplasty as previously mentioned. One other cusp repair technique used to treat annular dilatation is valve extension (Figure 13). Valve extension is completed by sewing a strip of pericardium, approximately 3 to 8 mm wide, depending on annular dilation, to the free edge of the valve leaflet to increase surface area for coaptation.[7]

Figure 13

Valve Extension. A strip of pericardium is sewn to the free edge of a valve leaflets to increase surface area for coaptation.

Stenosis. Management of restrictive cusp pathology due to calcification, inflammation, or rheumatic disease can be more difficult to repair. Localized shaving and decalcification can be used to unroll the free edge of thickened leaflets and allow better coaptation (Figure 14). A scalpel is used to release the free edge and unroll or thin out the edge to allow the cusps to come together.[7]

Figure 14

Localized Shaving and Decalcification. A scalpel is used to release the free edge (AandB) and unroll or thin out the edge (C) to allow the cusps to come together. Primary reapproximation is applied as needed (D).

When it is not possible to shave or decalcify, such as in the setting of endocarditis, localized resection including commissurotomy can be performed with the placement of patch material for cusp restoration. Cusp enlargement for stenosis or cusp retraction with pericardium and Dacron has been described but long-term data are needed.[120],[145],[146],[147],[148],[149],[150],[151],[152],[153]

Perforation, Tears, or Fenestrations

Cusp perforations and tears are usually caused by infection or direct trauma. Theses injuries may be repairable, provided the cusp tissue adjacent to the injury is strong enough to hold the suture. Perforations or tears caused by endocarditis often require wide debridement of infected tissue and may ultimately not be suitable for valve repair. Defects can be primarily repaired if there is enough redundant tissue to allow for linear closure; otherwise, they can be patched with autologous or bovine pericardium.[96],[145],[146],[147] Bovine pericardium, although thicker, can be prone to calcification.

Fenestrations can be left alone if small and causing no eccentric regurgitation, where focus should be on fixing cusp length, annuloplasty, and/or commissuroplasty. Large fenestrations that cause an eccentric jet may require intervention, or on the contrary, may exclude repair. Reinforcement sutures (usually 6-0 or 7-0 polypropylene) have been used to stabilize a fenestration by running the entire length of a cusp from 1 commissure to the other.[132],[141] Autologous pericardial patch has been used for congenital fenestrations.[154],[155] However, in patients with acquired fenestrations, such as large aortic root aneurysms and Marfan syndrome, patch repair is often less amenable because the cusp tissue is typically stretched, thinned, and does not hold suture well.

Repair of Anomalies Including Bicuspid

Bicuspid valves have the potential to be more straightforward to repair than tricuspid valves because they tend to have 1 redundant cusp that is usually durable enough to tolerate repair manipulations.[1] Furthermore, only 1 coaptation line needs to be considered rather than 3.

Repair of type 0 valves is dependent on the degree of prolapse assessed by comparing the prolapsing cusp to the nonprolapsing cusp. If both cusps are prolapsing, the height of coaptation should be restored to the midpoint of the sinuses of Valsalva using free margin plication or free margin suspension. If upon assessment of the valve the pathophysiology is restrictive, the thickened and fibrotic areas are shaved and decalcified.

Repair of type 1 valves requires addressing the median raphe first. If the raphe is relatively mobile with fibrous prolapsing, it can be preserved and shaved using a scalpel and scissors. If the valve is severely restrictive or calcified, a triangular resection can be completed. The remaining cusp tissue is then assessed. If adequate cusp tissue is present, the edges of the leaflet can be reapproximated primarily using running locked or interrupted 6-0 polypropylene sutures. If adequate cusp tissue is not present, an autologous treated or bovine pericardial patch may be used. The final valve-free margins are assessed using the alignment techniques discussed previously. If required, free margin plication or resuspension can be used to correct any remaining deformities. Additionally, creative repair techniques, such as the inverted neochordal repair technique, may be adopted for select patients.[124] In this repair technique, a polytetrafluoroethylene suture is placed at the fused cusp margin and sewn toward the malformed commissure. The suture tails are tied and then anchored to the aorta at the malformed commissure apex. This forms a suspensory neochord. The length of the neochord can be adjusted before securing it with knots to ensure that proper coaptation is achieved. Repair of type 2 valves is an extension of the previous described techniques based on visible anatomy.

Unicuspid and quadricuspid aortic valves exist as rare anomalies, and similar to bi- and tricuspid valves can manifest as stenosis or regurgitation. For unicuspid valves, creating a neocommissure using a pericardial patch and “bicuspidization” typically repairs the defect. Furthermore, both single and double patch techniques have been used, with the highest application of these procedures being done in the pediatric and young adult population.[29],[156]

Quadricuspid valves can present in a variety of orientations and are often associated with aortic pathology. Most often 1 of the cusps has an additional attachment to the aortic wall and a raphe that causes restriction. Taking down this attachment and “tricuspidizing” the valve is an appropriate repair approach.[27],[29],[157],[158],[159],[160],[161]

A video showing minimally invasive BAV repair can be found here:

A video showing repair of a BAV with associated coronary anomalies can be found here:

Valve-Sparing Root Replacement

Aortic valve competence is not only dependent on cusp coaptation but also relies on the entire aortic root apparatus functioning normally. Therefore, aortic valve repair in conjunction with valve-sparing aortic root replacement allows restoration of function to all of the components of the valve to promote competence.[1] The clearest indication for concomitant valve repair and root replacement is the presence of eccentric aortic insufficiency and a root aneurysm.

Starting in 1979 by Yacoub with aortic root remodeling and continuing in 1988 by David with the reimplantation method of preserving the patient’s native aortic valve when replacing aortic root aneurysms, both procedures have grown in popularity and proven to be applicable to a broad spectrum of patients with aortic root pathology.[8],[10],[11],[98],[162],[163],[164],[165],[166] Since the original descriptions of these 2 strategies, valve-sparing root replacement techniques have been modified but are generally classified as either remodeling or reimplantation.[1] The reimplantation technique of root replacement when combined with valve repair offers the advantage of restructuring the entire root apparatus with a single graft when compared with remodeling and is, hence, discussed first in this text.

Reimplantation

Valve-sparing root replacement with “reimplantation” of the valve and its annulus into a tube graft was initially described by David.[164],[167],[168] The reimplantation technique traditionally creates the most stable form of functional aortic annuloplasty for valve-sparing root replacement, and the basic procedure is outlined as follows (Figure 15 and video):

Figure 15

Aortic Reimplantation. The aortic root is dissected as low as possible as defined by the natural anatomic limitation of root insertion into ventricular muscle. The pathologic aortic root is transected as defined by the dotted lines and the coronary buttons are harvested (A). The alignment examination is completed using 3 traction sutures placed at each commissure (B). A Dacron graft is appropriately sized and the native aortic valve is reimplanted directly into the graft (C). The coronary buttons are reattached and the graft is secured to the ascending aorta (D).

1. Aortic Root Preparation – The main steps to preparing the aortic root include dissection, Valsalva resection, and coronary button harvest. Dissection around the root externally should extend as low as possible as defined by the natural anatomic limitation of root insertion into ventricular muscle. Typically the root dissection is started along the noncoronary sinus and continued toward the left-coronary and noncoronary commissure. The subannular region of the aortic valve is fibrous in this area and allows the dissection to be extended below the level of insertion of the leaflets. The dissection extending toward the right coronary and noncoronary commissure, as well as the right coronary and left coronary commissure is somewhat limited by nonfibrous portions of the annulus. Once the root is dissected, cannulas are placed, cardiopulmonary bypass is started, the distal ascending aorta is cross-clamped, and the more proximal ascending aorta is transected. The sinuses of Valsalva are then resected, leaving approximately 5 mm of aortic wall attached to the leaflet insertions, and the coronary buttons are harvested from the resected sinuses.

2. Prosthesis Sizing – As described in the previous alignment examination section, 3 commissural traction sutures are placed and pulled superiorly and perpendicular to the annular plane to establish good leaflet coaptation. Two primary methods exist for sizing: (1) A Hagar dilator is used to measure the circumference of the 3 commissures, and a graft 4 mm larger is chosen to sit outside the commissural posts; and (2) the height of the commissure (from the base of the interleaflet triangle to the top of the commissure) is measured and used as an equivalent measurement of the diameter of the STJ.[169] This measurement relies on the fact that despite various components of the aortic root and functional aortic annulus dilating in the setting of root aneurysms, the height of the commissure remains relatively constant. The height of the commissure can be most easily measured at the noncoronary and left coronary commissure by first drawing a connecting line between the nadirs of the 2 adjacent cusps (base of the interleaflet triangle) and measuring the distance between this line and the top of the commissure. This height corresponds to the diameter of the chosen graft.

3. Proximal Suture Line – Nonabsorbable, typically 2-0 sutures are placed from inside to outside the aorta. The initial suture is typically started at the noncoronary and left coronary commissure and moved clockwise. For both the left coronary and right coronary as well as the right coronary and noncoronary subcommissural triangles, the sutures follow the nonfibrous portions of the annulus where the external dissection of the root is limited by muscle. However, for the left coronary and noncoronary commissure, the sutures are placed horizontally across the base of the interleaflet triangle due to the fibrous nature of the aortic annulus at this point.

4. Prosthesis Preparation and Fixation – A Dacron graft is used as the primary prosthesis and can be used with or without premade neoaortic sinuses. Attaching the 3 commissures along the same graft plane creates the new STJ, reestablishing the commissural height previously measured. Tailoring of the graft first occurs by measuring the distance from the base of the interleaflet triangle to the top of the left-coronary and noncoronary commissure and marking this distance on the graft. At the right-coronary and noncoronary and right-coronary and left-coronary commissures, the distance from the proximal suture to the top of the commissure is measured and used to determine the amount of graft material required to trim. The sutures are then passed through the base of the graft, and the graft is slid down externally over the spared valve. Tension on the commissural traction sutures is required while tying down the graft to ensure appropriate seating around the annulus.

5. Valve Reimplantation – Each of the commissures is reimplanted using 4-0 polypropylene pledgeted sutures. Care is taken to ensure the native commissures are pulled up into place and valve coaptation is satisfactory. Note that the precise position of each commissure is crucial to establishing proper coaptation plane. A recent biomechanical engineering study evaluated the impact of commissure geometric alignment on cusp prolapse and aortic regurgitation.[170] This study demonstrated that when commissure heights were changed from the optimal position with concomitantly reduced inter-commissure angle, aortic cusp prolapse with regurgitation was most prominent. Care should be taken when choosing the location to resuspend each commissure. Fine adjustments may be needed to respect the native aortic valve root geometry. A running suture line is started at the nadir of each sinus. Small regular steps are made, passing the suture from outside the prosthesis to inside and through the aortic wall, staying close to the annulus, and back out again. The running sutures are tied at each commissure.

6. Leaflet Assessment and Repair – After the aortic valve has been reimplanted into the graft, the leaflets are examined for prolapse, symmetry, and the height and depth of coaptation. If prolapse is present, it can be repaired using the techniques previously described, including free margin plication and free margin resuspension. Root pressure and signs of left ventricular dilation can be assessed by flushing cardioplegia through the distal end of the graft to distend the new aortic root. Limited echocardiography should be completed to give qualitative assessment.

Following a satisfactory assessment of the leaflets, 2 ostia sites are created in the graft using electrocautery, each in their respective grafted right- and left-coronary sinuses. The ostia are then reimplanted into the graft. The distal end of the implanted graft is aligned with the transected aorta, and any excess graft material is excised. The graft is then anastomosed to the distal ascending aorta in the standard fashion. The cross-clamp is removed, and the steps of cardiopulmonary bypass reversal are completed.

Graft Options for Reimplantation

Besides straight Dacron grafts, there are grafts with pre-formed neosinuses that are commercially available. They include the Gelweave Valsalva graft (Vascutek, Inchinnan, United Kingdom) and the Cardioroot graft (Atrium Medical Corporation, Hudson, New Hampshire)[171] (Figure 16). Some surgeons have found these grafts to be helpful, whereas others have not used them secondary to the belief that they deform the aortic annulus, leading to a curved shape and potentially compromising the durability of the repair. Another concern of these grafts is that the height of the sinuses may not coincide with the height of the native aortic valve commissures, thus creating other technical and anatomic problems.[80] Dacron graft with anatomic sinuses called UniGraft W SINUS (Braun, Melsungen, Germany) is also available in Europe.[14],[172] One study using 4-dimensional cardiac magnetic resonance imaging in patients who had reimplantation procedures done with this graft showed fairly normal flows and nearly physiologic sinus vortex formation and transvalvular pressure gradients.[173] However, there is minimal global experience with this graft, and further studies are needed to evaluate its geometric shape as Dacron tends to increase in diameter over time.[174]

It has been hypothesized that the absence of the sinuses of Valsalva are postulated to perturb coronary flow patterns and create abnormal leaflet stress, which ultimately may limit the long-term durability of valve-sparing aortic root replacement.[15] David refined his original reimplantation procedure to create pseudosinuses (David-V technique) using a much larger graft that is tapered down, or plicated, at the annular and STJ levels.[98],[99] The Stanford modification of the reimplantation technique was created using 1 large graft and 1 small graft, which create large billowing Dacron pseudosinuses similar to the reimplantation procedure with a Valsalva graft[175],[176] (Figure 16).

Lastly, the anticommissural plication technique was developed to also recreate neosinuses but by using a specific formula for graft sizing based on cusp height.[177] A oversized straight Dacron graft is plicated between the commissures at the nadir of each sinus at both the annular level and the sinotubular junction.

A comprehensive mechanical engineering study investigated aortic valve leaflet opening and closing velocities after the valve-sparing aortic root replacement procedure using 5 different conduit configurations, namely straight graft, Valsalva graft, anticommissural plication, Stanford modification, and Uni-Graft.[178] Using a validated ex vivo heart simulator, the authors found that the straight graft, although makes no attempt to mimic native aortic root neosinuses, appears to perform most closely to the native aortic root in terms of cusp velocity and forces. This may imply less wear on the valve cusps, which could result in superior clinical durability over conduit configurations with higher cusp velocities and forces. Future studies are underway to further evaluate leaflet fluttering and coronary flow using the different conduit configurations.

Figure 16

Aortic Reimplantation with Valsalva Graft. Dacron grafts with cylindrical neosinuses are commercially available and include the Gelweave Valsalva graft (Vascutek Ltd., Inchinnan, United Kingdom) and the Cardioroot graft (Atrium Medical Corporation, Hudson, New Hampshire).

A video showing aortic root replacement can be found here:

A video showing valve-sparing aortic root replacement in the presence of coronary anomalies can be found here:

A video showing the reimplantation procedure can be found here:

Remodeling

Yacoub’s technique of valve-sparing root replacement, which he termed “remodeling,” involves replacement of the sinus segments with a scalloped polyester graft.[163] Chronologically, remodeling was described before the reimplantation technique and has been shown to be procedurally simpler. Many of the steps are the same as reimplantation with the overall exception that the Dacron graft is cut to the shape of 3 neoaortic sinuses and brought directly down to the leaflet bases without reimplanting the remaining valve inside the graft (Figure 17).

Figure 17

Aortic Remodeling. The aortic root is dissected and transected using the same steps as the reimplantation technique (see Figure 13 – AandB). A Dacron graft is cut to the shape of the 3 neoaortic sinuses (A) and brought directly down to the leaflet bases without reimplanting the remaining valve inside the graft (B). A continuous suture is then run circumferentially to attach the remnant of the aortic annulus (C). The coronary arteries are reimplanted into their respective sinuses and the graft is secured to the ascending aorta (D).

The aortic root is dissected circumferentially down to the level of the aortic annulus as described in the reimplantation technique. The 3 aortic sinuses are excised, leaving approximately 4 to 5 mm of tissue attached to the aortic annulus and around the coronary arteries. The 3 commissures are gently suspended upward and approximated using the alignment technique until the cusps coapt. The diameter of an imaginary circle that includes all 3 commissures is approximately the diameter of the Dacron graft to be used for reconstruction. One end of the graft is cut to create neoaortic sinuses. The widths of the sinuses are based on the measured distance between each commissure. The height of the commissures should be approximately equal to their width. The 3 commissures are then attached on the outside of the graft immediately above the neoaortic sinuses. A continuous 4-0 polypropylene suture is then run circumferentially to attach the remnant of the aortic annulus. The coronary arteries are reimplanted into their respective sinuses. If there is any misalignment of the cusps after these steps, the misalignment can be addressed by the repair techniques previously mentioned.

Stanford modification of reimplantation

Starting in December 2002, the Stanford modification of the reimplantation technique, or T. David-V technique, was created using 1 large graft and 1 small graft, which create large billowing Dacron pseudosinuses similar to the reimplantation procedure with a Valsalva graft[175],[176] (Figure 14). This modification was created to address the possible negative effects of the absence of the sinuses of Valsalva with the traditional reimplantation technique. Analysis of the results after reimplantation and remodeling methods have shown that the reimplantation technique is more hemostatic, provides more reliable annular stabilization, and might be associated with better long-term durability.[99],[106],[163],[164] However, the remodeling procedure has the theoretical advantage of recreating the sinuses of Valsalva. The absence of the sinuses of Valsalva are postulated to perturb coronary flow patterns and create abnormal leaflet stress, which ultimately may limit the long-term durability of valve-sparing aortic root replacement.[15] David refined his original reimplantation procedure to create pseudosinuses (David-V technique) using a much larger graft that is tapered down, or plicated, at the annular and STJ levels.[98],[99] This technique was taken a step further by Craig Miller, MD, and has become known as the Stanford modification where 2 grafts of different sizes are used to recreate the sinuses of Valsalva and facilitate suturing the valve inside the graft, as well as the distal graft to aorta anastomosis.

The details of the Stanford modification can be found in Demers and colleagues.[175] However, in brief, after dissection of the aortic root, the sinuses of Valsalva are excised and the necessary graft diameter is calculated using David’s original formula.[164] A graft 6 to 8 mm larger than the calculated size is then tapered down proximally with 9 to 10 interrupted 5-0 braded sutures using a commercial valve sizer as a guide inside the graft. Using 12 to 14 polyester 2-0 mattress sutures placed immediately below the lowest level of the valve leaflets, the graft is then implanted at the base of the aortic root. The valve and coronary buttons are then reimplanted in standard fashion, and the large graft end is amputated immediately above the tops of the commissures. A second smaller graft is matched to estimate the diameter of the neosinotubular junction. Sewing the distal end of the large graft to the second small graft with a continuous 4-0 polypropylene suture recreates the pseudosinuses. The final anastomosis connects the opposite end of the smaller graft to the distal ascending aorta (Figure 15).

Remodeling with external ring annuloplasty

Whereas the Stanford modification attempts to overcome the weaknesses of the initial reimplantation technique, Lansac and colleagues have described a combination technique using external ring annuloplasty to overcome the inherent weaknesses of the remodeling procedure.[126],[179],[180] The reimplantation technique performs external subvalvular aortic annuloplasty but withdraws the sinuses of Valsalva and includes the interleaflet triangles within a tube graft, thus risking impairment of root dynamics.[15],[16],[181],[182],[183] In contrast, the remodeling technique has the benefit of providing more physiologic movements of the cusps with preservation of root expansibility throughout the cardiac cycle but does not entirely address annular base dilation.[184],[185] By adding an external annuloplasty ring that has the capability of maintaining a calibrated diameter in diastole and expansibility during systole, the physiologic benefits of the remodeling procedure can be obtained in combination with treating annular base dilation.[180] The procedure is completed by placing 6 subvalvular U-anchoring stitches after dissection of the subvalvular plane during the remodeling procedure. These stitches are placed internally across the aortic root. After the remodeling procedure has been completed to the point of suturing the prosthesis into the aortic root, the 6 anchoring U-stitches are passed through the inner aspect of the prosthetic expansible aortic ring. The ring is then descended around the remodeled aortic root and the U-stitches are tied to secure the ring in its subvalvular position.

Non-Valve-Sparing Root Replacement

To treat an aneurysm of the ascending aorta, in 1964, Wheat and colleagues were the first to perform a successful replacement of the aortic valve in continuity by separate graft valve repair.[186] During the same time, Groves and colleagues introduced the supracoronary method that was later followed by the inclusion technique for repair of aortic aneurysms.[187],[188] In 1968, Bentall and De Bono described the total replacement of the ascending aorta and aortic valve with a composite tubular graft containing a prosthetic valve with reimplantation of the coronary ostia to the graft.[189],[190],[191] Many of the steps are similar to the previously described techniques with the exception of the aortic cusps being excised. After the coronary arteries are detached from their sinuses, a Dacron conduit is once again used but with a valve already attached to one of its ends. The valved conduit is sutured to the aortic annulus, and the coronary arteries are reimplanted into the graft.

In younger patients, manufactured mechanical valves have often been preferable, and in patients with a strong indication for avoiding anticoagulation, a bioprosthetic valve can be sewn into a Dacron graft without complication.[192],[193],[194] When using a bioprosthetic valve, the valve can be secured to the aortic annulus at the same time as the Dacron tube or it can be secured inside the tubular Dacron graft approximately 1 cm from one of its ends, and the graft alone can be sewn to the annulus. When using a bioprosthetic valve in this manner, it allows for the possibility of aortic valve re-replacement without the requirement of taking down the original graft or coronary arteries when the bioprosthetic valve fails. Pulmonary autografts are not recommended for this procedure due to the risk of aneurysmal dilatation when the autografts are subjected to systemic pressures.

Aortic root replacement has gone through much iteration over the past decades. When Bentall and De Bono initially described their procedure, they opened the aneurysm and sutured a Teflon graft containing a mechanical valve to the aortic annulus. The graft was also sutured to the aortic sinus wall around the orifice of the coronary arteries. The aneurysmal wall was then wrapped around the graft and closed over for hemostasis. However, the procedure was complicated by pseudoaneurysm formation of the aortic anastomoses and coronary arteries.[195] Attempts to limit these psuedoaneurysms were done by Cabrol and colleagues when they created a shunt between that space and the right atrium.[196] The practice of root replacement then transitioned to eliminate wrapping the graft with the aneurysm wall to avoid tension on the anastomoses with the accumulation of blood. During this time, Cabrol and colleagues also described a technique of connecting the 2 coronary arteries with a smaller graft and anastomosing the graft side to side with the valved conduit.[197] However, the long-term results were not as good as direct coronary artery reimplantation, which is the current most widely used technique.[198]