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Aortic valve replacement (AVR) is the most common valve replacement procedure and the second most common cardiac operation following coronary artery bypass grafting (CABG) in the United States. Intraoperative transesophageal echocardiography (TEE) alters the surgical plan in 13% of patients undergoing aortic valve surgery.1 Furthermore, a consensus statement from the American College of Cardiology, American Heart Association, and American Society of Echocardiography gave intraoperative TEE a class I designation (“evidence and/or general agreement that a given procedure or treatment is useful and effective”) in patients undergoing surgical repair of valvular lesions.2 Thus, a comprehensive TEE evaluation of the aortic valve should be performed in all patients, particularly those undergoing aortic valve procedures.
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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- (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 post-bypass examination provides rapid assessment of the adequacy of the valve repair/replacement and any associated cardiac complications. Intraoperative examination thus aids surgical decision making, and is especially helpful in determining the feasibility of aortic valve repair versus aortic valve replacement.
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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 the aortic valve. The aortic valve apparatus is comprised of the left ventricular outflow tract (LVOT), valve cusps, sinuses of Valsalva, and proximal ascending aorta (Figure 9–1). The LVOT consists of the inferior or ventricular surface of the anterior mitral leaflet, the interventricular septum, and the posterior left ventricular free wall.
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A normally functioning aortic valve apparatus allows unrestricted blood flow from the left ventricle to the ascending aorta during systole and prevents retrograde blood flow from the aorta to left ventricle during diastole. Stresses during diastole are distributed across the leaflets to the commissures and into the sinuses of Valsalva. The sinuses of Valsalva also play a critical role in systole by allowing the aortic valve to open fully without contacting the walls of the aorta. Disruption in this normal anatomy or mechanisms leads to valve dysfunction. In late diastole and associated LV filling, a 12% expansion of the aortic root is observed immediately prior to aortic valve opening,3-5 which actually initiates leaflet opening prior to ventricular contraction.3,6
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