Pulmonary venous drainage and its successful connection to the left atrium is the product of an embryologic process which is completed within the first 30 to 48 days of gestation. Four fully formed pulmonary veins open into the posterior aspect of the left atrial cavity and this connection is also associated with a correct axial orientation of the interatrial septum. Any deviation from this morphologic connection gives rise to an anomalous pulmonary venous connection.[6] Such an anomalous connection usually brings drainage of the pulmonary veins to the systemic venous side of circulation, creating a physiologic left to right shunt. The anomaly is classified as “total” anomalous pulmonary venous connection when none of the pulmonary veins morphologically connect to the left atrium and “partial” when some are connected normally and some anomalously.

Partial Anomalous Pulmonary Venous Connection (PAPVC)

Partial anomalous pulmonary venous connection is often associated with a sinus venosus atrial septal defect and most commonly with anomalous drainage of a portion of the R sided pulmonary venous return. However, PAPVC can also occur without presence of any atrial level communication. Drainage of R inferior pulmonary vein into IVC is often referred to as “Scimitar Syndrome” and is often associated with hypoplasia of the right lung (Figure 1).

Figure 1

Forms of Partial Anomalous Pulmonary Venous Return (PAPVC).

(A) Sinus Venosus PAPV with connection from R pulmonary veins to SVC.[7]

(B) Right Pulmonary Vein to IVC in Scimitar Syndrome.[8]

Total Anomalous Pulmonary Venous Connection (TAPVC)

Total anomalous pulmonary venous connection is classified based upon the anatomic route the pulmonary venous blood takes anomalously to the systemic venous circulation (Figure 2).

• Supra-cardiac: via ascending vertical vein and into innominate vein
• Cardiac: via pulmonary venous confluence connection into R atrium / coronary sinus
• Infra-cardiac: via descending vertical vein and into portal venous system
• Mixed: varying forms of anomalous drainage for each lung

Figure 2

Variants of total anomalous pulmonary venous connection (TAPVC).[9]

(A) Supracardiac: both right (RPV) and left (LPV) pulmonary veins join a common pulmonary venous confluence behind the heart, which drains via a vertical vein to the undersurface of the left innominate vein, and thence to the right atrium.

(B) Cardiac: the pulmonary venous confluence connects to the coronary sinus (CS), and thence to the right atrium via the coronary sinus ostium.

(C) Infracardiac: the pulmonary venous confluence drains inferiorly via a vertical vein to the portal vein (PV) or hepatic veins (HV) and thence to the right atrium.

(D) Mixed connections: left pulmonary veins drain to the left innominate vein (LIV), and right pulmonary veins to the coronary sinus in this example. IVC, inferior vena cava; SMV, superior mesenteric vein; SV, splenic vein.

Chest Radiography

Cases of PAPVC are due to R sided pulmonary veins draining into the systemic venous circulation. An example of this is when drainage is into the IVC and subsequently into the right atrium. This scenario has been described in CXR findings as “Scimitar Syndrome” (Figure 3).

Figure 3

CXR findings of Scimitar Syndrome – Turkish Sword.[10]

Unobstructed TAPVC may reveal pulmonary vascular congestion and a large cardiac silhouette. The “snowman” finding on chest radiograph is secondary to mediastinal and cardiac enlargement associated with prominent pulmonary arterial vasculature as well as the potential for a prominent SVC which is often found in cases of supracardiac TAPVC (Figure 4).

Figure 4

Snowman sign in Supracardiac TAPVC.[11]

Chest radiographs of patients with obstructed TAPVC will commonly reveal severe pulmonary edema in the presence of a normally sized and shaped cardiac silhouette (Figure 5).

Figure 5

Obstructed TAPVC with associated pulmonary venous congestion.[11]

Echocardiography

Two dimensional and doppler echocardiography is the primary diagnostic tool for most patients with anomalous pulmonary venous connections. Findings are commonly a combination of a distended right ventricle, some form of pulmonary vascular confluence with abnormal or absent drainage to the left atrium on doppler interrogation. Often, there is concomitant presence of an accessory common vein or dilated coronary sinus. In addition, echocardiographic evaluation may reveal turbulent flow in the right atrium with right to left atrial level shunt. In supracardiac TAPVC, with a left sided vertical vein draining to the innominate vein, the course of the vertical vein relative to the left pulmonary artery (LPA) is highly important. If coursing anterior to the LPA, obstruction is rare. However, if posterior to the LPA, compression (and thus obstruction) of the vein between the LPA and bronchus is essentially uniform.

CT Angiography (CTA) / Magnetic Resonance Angiography (MRA)

In non-emergency cases of TAPVC and PAPVC, contrast enhanced CT may be helpful to provide a complete anatomic diagnosis (Figure 6 and Figure 7). These modalities detail accurately the pulmonary venous anatomy and specifics regarding drainage patterns. From a functional standpoint, MRA may allow for quantitative determination of the amount of anomalous drainage and a resultant calculated Qp:Qs which may be more helpful in cases of PAPVC regarding delineation of operative indications. Additionally, MRA may also reveal pulmonary arterial and venous size as well as information regarding ventricular size and function.

PAPVC is often associated with drainage of the right superior and or middle lobe pulmonary veins into the SVC. This is often best delineated via use of CT angiography as an adjunct to echocardiography. More specifically, it allows for surgical planning and pre-operative counseling as to technical considerations for repair.[10]

Figure 6

CTA findings of PAPVR with right sided pulmonary venous drainage into the SVC.[10]

Figure 7

CT Angiography findings in Total Anomalous Pulmonary Venous Connection.[11]

(a) Supracardiac with ascending vertical vein in to SVC.

(b) Infracardiac with descending vertical vein into portal system below diaphragm.

(c) Mixed picture with R and L pulmonary veins taking independent course for drainage into R atrium.[10]

PAPVC

The timing of repair for PAPVC is a product of clinical and physiologic signs and symptoms. The presence of an atrial level communication, often times a sinus venosus atrial septal defect (ASD), may yield a more significant Qp:Qs and thus lead to an earlier approach at surgical repair. Adults who present with single vein PAPVC and no significant atrial level communication may not have concerning findings of right sided enlargement nor significant pulmonary over-circulation and thus may be followed without surgical intervention.

Non-Obstructed TAPVC

A focus on early primary surgical repair is universally supported, prior to cyanosis as well as right sided volume overload issues become more prominent. In a majority of cases, definitive repair is undertaken during the same hospitalization as time of diagnosis unless other significant comorbidities preclude such a strategy.

Obstructed TAPVC

Due to a lack of effective medical palliation, a neonate with obstructed TAPVC should be taken to the operating room immediately after confirmed echocardiographic diagnosis. As such, it is considered a surgical emergency. In extreme cases where such surgical support is not available, Extracorporeal Membrane Oxygenation (ECMO) may provide some form of clinical stability or end organ recovery prior to surgical intervention. If necessary, ECMO can also be employed as a posto-perative tool in the setting of low cardiac output syndrome to allow the left ventricle to become accustomed to being responsible for post reparative full cardiac output.

PAPVC

Operative management and strategies employed for repair should be the product of a thorough pre and intra operative assessment of the anatomic variables associated with the partial anomalous pulmonary veins themselves, the entrance they have into the right atrium, atrial anatomy as well as the presence or absence of an atrial level communication.

Pulmonary Venous Anatomy: If the anomalous pulmonary veins from the right lung enter into the right atrium directly, or at the cavo-pulmonary junction, an intra cardiac baffling of the pulmonary venous blood through an atrial level communication may be feasible. If on the other hand, the entrance is into the SVC remote from the right atrium, two separate techniques may be considered.

The first approach is a “two patch technique” which preserves the SVC to R atrial connection (Figure 8). The initial atriotomy performed lateral and posterior to the SVC and R atrial junction provides exposure for an intra-cardiac patch to baffle pulmonary venous blood through an atrial level communication into the L atrium. Subsequently, a second patch is employed to augment the systemic venous channel from the SVC into the right atrium and is fashioned to avoid systemic venous obstruction secondary to the internal baffle. Attention is given to avoiding injury to the sino-atrial node.

Figure 8

Two Patch Technique for PAPVC repair: First patch baffling anomalous pulmonary veins and closing the sinus venosus atrial septal defect. Inset: Second patch enlarging the SVC – R atrial junction.[19]

The second approach would require formal division of the SVC. This approach is often part of the Warden procedure which is described below (Figure 9). In addition, should the SVC require division, the atrial opening may be patch augmented to allow for a more unobstructed pathway for pulmonary venous blood flow into the atrium.

Atrial Anatomy: As mentioned previously, an atrial level communication may or may not be present in association with PAPVC. If not present, one must be surgically created to allow for a pathway to be constructed into the left atrium. In addition, in cases of a small atrial appendage, the Warden procedure may require patch augmentation to ensure the SVC to atrial appendage anastomosis is not the cause for future systemic venous obstruction.

The Warden Procedure has been described for repair of PAPVC involving the right upper and / or middle lobe pulmonary veins draining into the SVC with an associated sinus venosus ASD.[20] This procedure requires bicaval cannulation and complete cardiopulmonary bypass support. Caval snares may be placed and secured to completely exclude the heart.

Prior to arrest of the heart, the SVC may be divided carefully to ensure the transection is completed just proximal to the entry point of the anomalous pulmonary vein(s). The cardiac or distal side of the SVC may be over-sewn with a running Prolene suture. The aortic cross clamp is now placed and cardioplegia delivered. The right atrium is opened and the sinus venosus ASD identified. If an adequate atrial level communication is not present, one is created or enlarged. Patch material at the discretion of the surgeon is now employed to baffle the pulmonary venous blood across the ASD and towards the left atrium which in essence will concomitantly close the ASD. The proximal SVC is anastomosed to the right atrial appendage to allow for an adequate pathway for upper body systemic venous drainage. This suture line may be tied over a dilator to ensure there is no subsequent narrowing of this anastomosis. Such a narrowing resulting in SVC obstruction is cited as the most common long-term morbidity of this operative approach.

Figure 9

Warden Procedure for PAPVR.[6]

Video description of the Warden Technique has been described.[21] Minimally invasive approaches to repair of PAPVR via bilateral anterolateral mini-thoracotomies have also been described.[22]

Several management strategies have been proposed for Scimitar Syndrome. A method of correction was described by Zubiate where patch material was employed to baffle flow from the anomalous vein in the IVC through the right atrium and into the ASD to redirect this pulmonary venous flow into the left atrium. The major drawback to this technique was the length of the baffle and concerns for IVC systemic drainage obstruction.[23] In addition, baffle thickening and or scarring may ultimately lead to pulmonary venous obstruction.

Schumaker described excising the anomalous pulmonary vein with a cuff of IVC and re-implanting it on the atrium directly and then creating an intracardiac baffle to the left atrium via the ASD. The IVC is then patched to avoid narrowing or obstruction.[24]

Gudjonsson and Brown described a technique where the 5^th intercostal space is entered via a lateral thoracotomy. The right lung if freed of adhesions and the anomalous vein is dissected out to its thoracic course for mobilization. With the right pulmonary artery encircled and the patient heparinized, the anomalous vein is excised from the IVC and implanted directly into the left atrium, which is approached via a window created in the pericardium posterior to the phrenic nerve. An end to side anastomosis is created between the anomalous vein and the left atrium directly with control of the heart with a curved vascular clamp.[7]

TAPVC

Infracardiac TAPVC

Infracardiac TAPVC is the most common form of obstructed TAPVC and in this clinical scenario considered a surgical emergency. Patients thus present in the immediate neonatal period and are relatively unstable as has been described due to metabolic acidosis, significant hypoxia and circulatory collapse. In cases where there is no sign of pulmonary venous obstruction, a more elective approach to repair during the same hospitalization may be considered.

Repair of all types of TAPVC requires use of continuous cardiopulmonary bypass (CPB) and moderate systemic hypothermia. This is especially true for intracardiac TAPVC where pulmonary venous return to the right atrium is via the coronary sinus. In other cases of TAPVC, surgical intervention often requires better visualization of the pulmonary venous confluence and all pulmonary veins and the need to create a more blood less environment. As such, many surgeons advocate use of more aggressive hypothermia and even deep hypothermic circulatory arrest for neonatal repair of TAPVC.

Other technical considerations to keep in mind include ligation of a patent ductus arteriosus prior to or immediately following initiation of CPB. During the cooling phase, the heart may be elevated and rotated towards the right pleural space to expose the anomalous descending vertical vein often best located along the leftward posterior pericardial space. A Prolene suture may be placed at the apex of the heart to aid in gentle retraction. The posterior pericardium is opened and a vertical incision is made into the anomalous descending vertical vein associated with the pulmonary venous confluence. The vein as it extends into the abdomen is ligated with a silk suture. The heart may now be replaced into the mediastinum until full cooling is achieved.

The aorta may now be cross clamped and cardioplegia delivered for arrest and myocardial protection. Caval snares are secured around the SVC and IVC. The heart is once again elevated. A 6-0 Prolene suture may be placed into the left atrial appendage tip to again allow for gentle retraction. The left atrial appendage and left atrium are now opened and an anastomosis may be constructed between the left atrium and its appendage to the previously opened pulmonary venous confluence / descending vertical vein using a running 7-0 Prolene suture (Figure 10). The ASD may be closed prior to this anastomosis via the left atrium or after the anastomosis by opening up the right atrium following repositioning of the heart into the mediastinum.

Figure 10

Repair of Infracardiac TAPVC:

(A) Schematic illustration of defect.[19]

(B) Schematic illustration of the correction of the defect.[19]

(C) Operative technique for correction of the defect.[19]

Thoughtfully prepared videos have been constructed to depict the correction of infracardiac TAPVC.[25]

Supra-Cardiac TAPVC

After achieving adequate hypothermia and arrest of the heart, a transverse incision is started near the base of the right atrial appendage and posterior to the atrioventricular groove. The incision is extended toward the interatrial groove and into the left atrium across the interatrial septum and ASD. The posterior wall of the left atrium is now incised transversely but not reaching the left atrial appendage (Figure 11).

The common pulmonary vein or confluence is identified and the pericardium overlying it is incised. The common vein is formally opened along a line similar to the incision in the posterior left atrial wall. 7-0 Prolene suture is employed to create an anastomosis of this posterior atrial wall to the pulmonary venous confluence. The atrial septum and the right atrial wall are sutured together to approximate the posterior edge of the right atriotomy. Patch material is now employed to enlarge the atrial septum and ensure unobstructed pulmonary venous return to the left atrium. The right atriotomy is now closed.

Figure 11

Repair of Supracardiac TAPVC:

(A) Schematic illustration of defect.[19]

(B) Schematic illustration of correction of defect.[19]

(C) Biatrial incision for total correction of the defect.[19]

Another technique for management of supracardiac TAPVC is referred to as the “superior” approach. After arrest and delivery of cardioplegia, the aorta is retracted leftward and the dome of the left atrium is exposed. A tie is placed on the left atrial appendage for traction. The posterior pericardium just superior to the dome of the left atrium is opened and the pulmonary venous confluence is identified and opened in a longitudinal fashion (Figure 12).

A 7-0 Prolene suture is employed to create an anastomosis between the confluence and a matching incision within the dome of left atrium. The ASD is closed via a right atriotomy. In either technique, the ascending vertical vein is encircled with a heavy silk suture during cooling and then ligated during rewarming. Care should always be taken to ligate the vein as far away as possible from the pulmonary venous confluence. In addition, caution should be exercised in ensuring avoidance of unintended injury to the phrenic nerve during dissection or ligation of the vertical vein.

Figure 12

Superior approach to supracardiac TAPVC via anastomosis of the posterior aspect of the left atrium to the pulmonary venous confluence.[19]

Cardiac TAPVC

Following arrest of the heart and delivery of cardioplegia, a generous right atriotomy is made and the edges appropriately retracted for exposure. The patent foramen ovale or ASD is identified as well as the coronary sinus. In most cases, the pulmonary veins drain directly into the coronary sinus and thus its orifice is generally somewhat enlarged.

The pulmonary venous blood is routed into the left atrium by enlarging the ASD and using a pericardial patch to baffle the anomalous blood into the left atrium (Figure 13). The atrial level defect may need to be enlarged by extending its inferior margin toward the inferior vena cava or common pulmonary vein orifice. Any incision to enlarge the coronary sinus orifice must be well away from the anterior margin of the coronary sinus to prevent damage to the atrioventricular node and the conduction system. Care should also be taken to ensure that in enlarging the ASD, the posterior wall of the left atrium is not inadvertently opened.

Figure 13

Repair of intracardiac TAPVC.[19]

(A) schematic illustration of defect.

(B) schematic illustration of correction of defect.

(C) operative view of the extension of the ASD to incorporate the coronary sinus.

(D) correction of the anomaly by roofing the septal defect and rerouting pulmonary venous drainage into the left atrium.

Surgical management of Mixed forms of TAPVC can be the most challenging and have been described in video formats.[26]

Arrhythmias

The incidence of post-operative dysrhythmias may be underreported. In particular, upwards of 29% of patients may show chronotropic impairment on exercise testing indicating sinus node dysfunction. Atrioventricular conduction delays and block are rare.[27] Long term follow-up of patients undergoing TAPVC with Holter studies may be of benefit to uncover supraventricular dysrhythmias as well as ventricular ectopy.[28] There does not appear to be any correlation between anatomic subtype, operative approach nor adequacy of repair with the incidence of dysrhythmias.

Pulmonary Hypertension

Restrictive pulmonary hypertension is a common post-operative physiologic challenge in patients following repair of TAPVC. The use of inhaled nitric oxide following separation from CPB as well as Sildenafil through and following extubation are examples of pulmonary vasodilator therapies employed to address this issue. In addition, patients may commonly be discharged to home with oxygen supplementation for longer term pulmonary vasodilator therapy.

Pulmonary Venous Stenosis

The most common post-operative complication and etiology for re-intervention is pulmonary venous stenosis.[29] Stenosis can be secondary to technical factors, anatomic or extrinsic compression or endocardial sclerosis. Risk factors for pulmonary venous stenosis have been described in various studies to include obstruction at time of presentation, small pulmonary venous confluence at time of repair, diffuse pulmonary stenosis and hypoplasia as well as mixed forms of TAPVC.

The sutureless technique of employing a pericardial in situ anastomosis to the re opened pulmonary venous confluence has shown promising results in regards to the operative re-intervention rates for pulmonary venous stenosis (Figure 14). Programs are now employing a sutureless technique to primary repair of TAPVC with the hopes of avoiding any manipulation or injury to pulmonary venous tissue or endothelium.[29]

Figure 14

Sutureless technique for repair of Infracardiac TAPVC:

(A) Venous confluence is retro-pericardial. Left atrial incision is extended into appendage.

(B) Posterior pericardium is opened and descending vertical vein ligated. Pulmonary confluence is opened and incisions are extended into each pulmonary vein.

(C) Atrial edge is sutured to pericardium and in a fashion avoid direct suturing of pulmonary veins.

Early Outcomes

Early outcomes for repair of TAPVC in infancy, as reported prior to 1970, were associated with mortality rates of > 50%.[30] During the 1970s, with improvements in CPB techniques and myocardial protection, many centers reported mortality rates between 10-20%.[31] Larger single and multicenter series published in the early 2000s have reported three-year survival rates of 85% and an incidence of recurrent pulmonary venous stenosis in 15-20% of patients. Risk factors for death have been identified as obstruction at time of presentation, younger age at operation, associated cardiac lesions and post operative evidence of pulmonary venous stenosis.[32],[33] Patients with single ventricle disease and heterotaxy, who also have associated TAPVC, are also known to have worse outcomes.[34]

The largest single center series that looked at long term outcomes for surgical intervention for TAPVC had a study cohort of 377 patients and reported a 14-year survival of 65 +/- 6%. Significant (p< 0.01) risk factors for post repair death included cardiac connection type, earlier era of surgical intervention, younger age at repair, need for epinephrine post operatively and post operative pulmonary venous obstruction. In particular, cardiac connection type had a p value of 0.007 associated with mortality. In the study cohort, 9% of patients required re operation with mixed type of presentation being most common (p=0.04).[33]

The single center experience with perhaps the longest degree of follow up reported a study cohort of 214 patients with follow-up available for 96% of operative survivors at an average of 13 +/- 9 years (range 1 month – 42 years) after their operation. Survival at 10 and 20 years was 88% +/- 2.2%. Freedom from reoperation at 20 years was 86% +/- 3.2% and all survivors were asymptomatic at a mean of 13 +/9 years after the operation.[35]

Outcomes data harvested from larger multi institutional consortiums reveal in hospital mortality for patients undergoing surgical correction of TAPVC at 13%. This data is a product of 2,191 patients over a 25-year period of time within the Pediatric Cardiac Care Consortium (PCCC). Overall, 29% of patients within the study cohort presented with obstructed TAPVC and their operative mortality was 26%.[36]