Pathophysiology of the Aortic Valve
The role of the aortic valve in cardiovascular physiology is to ensure proper forward flow of the blood ejected from the left ventricle, enabling the cardiac output to efficiently perfuse the body. An improperly functioning aortic valve may have grave consequences on myocardial performance with resultant symptoms of congestive heart failure and death. Aortic valve replacement (AVR) remains one of the most commonly performed procedures in cardiac surgery. The 2 major pathologic conditions involving the aortic valve are aortic stenosis (AS) and aortic regurgitation (AR). The etiology, signs and symptoms, and indications for aortic valve surgery are discussed for both conditions.
For severe AS, presence of symptoms remains the classic and strongest indication for valve replacement. Clinical entities within the category of severe AS, such as low-flow, low-gradient AS with and without left ventricular dysfunction, and extremely high jet velocity AS, are discussed along with their indications for valve replacement. Recently, stress testing is advocated during evaluation of severe asymptomatic stenosis to potentially unmask symptoms. Dobutamine stress echocardiography is used to determine left ventricular contractile reserve, and to rule out aortic valve “pseudostenosis” in patients with low-flow, low-gradient AS. The roles for these stress tests in the evaluation of AS are presented.
Severe AR can harbor a decade-long asymptomatic period before symptom onset, and similar to AS, surgery was previously only advised with symptoms onset. AVR is now recommended if reduced left ventricular ejection fraction (LVEF) or a certain degree of left ventricular dilatation is present. Newer data advocate for earlier surgical intervention and suggest even lower thresholds for intervention based on degree of ventricular dilatation.
Despite AS and AR being well-studied entities, improved diagnostic modalities, technologies, and clinical studies offer a new look at the course of these diseases, and lend to an evolution of AVR criteria. It is important for cardiac surgeons to be aware of the latest guidelines for valve replacement and the most up-to-date clinical testing for these disease entities. Cardiology and cardiothoracic services often work together to ensure that patients with aortic valve disease receive appropriate evaluation and follow-up, for optimal timing of valve replacement when indicated. The current guidelines and emerging concepts in the assessment of pathophysiology and indications for AVR will be discussed.
Sections of ABTS Curriculum Addressed:
212.3 Valvular anatomy
217.2 Risk assessment
241.2 Physiology of valves
241.3 Pathophysiology of valvular disease
241.6 Indications for operative management of valve disease
241.8 Results of surgery for valve disease
242.1 Diagnosis, investigation, and assessment of valvular heart disease
242.2 Determination of need and timing of surgical intervention for valve disease
242.4 Echo interpretation
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