Chapter 11: Aortic Valve

INTRODUCTION

In U.S. patients over the age of 65 years, the prevalence of moderate or severe aortic stenosis (AS) or aortic regurgitation is 4.1% and 3.0%, respectively.¹ Surgical aortic valve replacement (SAVR) is the most common valve replacement procedure and the second most common cardiac operation following coronary artery bypass grafting (CABG) in the United States. Demographic studies estimate the current potential population of patients suffering from severe AS needing an aortic valve replacement (AVR) is estimated at 350,000 and is forecasted to increase with our aging population.² Recent studies indicate that between 33% and 69% of patients with symptomatic aortic stenosis who may be potential candidates for valve procedures never undergo an intervention, suggesting that improved compliance with guidelines or expanded applications of technologies should increase valve procedures.^1,3,4 Utilization of transcatheter aortic valve replacement (TAVR) continues to increase and redefine the management of aortic valve disease in patients of various surgical risk.^2,5 Analysis of clinical practices in New York State demonstrated a 27% increase in surgical and transcatheter aortic valve replacements between 2011 and 2012, with a 146% increase in transcatheter approaches.⁶ Intraoperative transesophageal echocardiography (TEE) alters the surgical plan in 13% of patients undergoing aortic valve surgery.⁷ Furthermore, consensus statements from cardiology and thoracic surgery societies have given intraoperative TEE a class I designation (“evidence and/or general agreement that a given procedure or treatment is beneficial, useful and effective”) in patients undergoing surgical repair or replacement of valvular lesions.^2,8 Thus, a comprehensive TEE evaluation of the aortic valve should be performed in all patients, particularly those undergoing aortic valve procedures.

Intraoperative transesophageal echocardiography is utilized to evaluate aortic valve anatomy, valve function, and hemodynamics. A comprehensive exam includes an evaluation of valvular architecture using two-dimensional (2D) and three-dimensional (3D) imaging techniques. Stenotic and regurgitant valvular lesions and their associated hemodynamic perturbations are assessed with pulsed-wave and continuous-wave Doppler echocardiography. TEE evaluation of left ventricular function and ventricular filling yields accurate and rapid assessment in patients with altered left ventricular compliance due to long-standing aortic valve pathology. The immediate postbypass examination provides rapid assessment of the adequacy of the valve repair/replacement and any associated cardiac complications. Intraprocedural TEE for patients undergoing TAVR is utilized to aid in prosthetic sizing, catheter positioning within the annulus, and valve deployment within the outflow tract. Postimplantation TEE is utilized to determine the etiology and quantitate the degree of aortic regurgitation and to identify complications such as aortic dissection.⁸ Intraoperative and intraprocedural examination thus aids surgical decision making, and is especially helpful in determining the feasibility of aortic valve repair versus aortic valve replacement, regardless of technical approach (SAVR vs. TAVR).

AORTIC VALVE FUNCTION

A thorough understanding of the anatomy and function of the aortic valve apparatus is necessary to obtain the optimal benefit from transesophageal echocardiographic interrogation of ...