Over the past three decades, significant advances have been made with respect to the evolution of prosthetic heart valves and the manner in which they are evaluated in vivo. New materials and configurations of mechanical and biologic valves have improved the quality of life for patients around the world. However, despite the benefits they confer by replacing a diseased valve, all prosthetic valves have inherent limitations and possible complications that may develop in the immediate or late post-implantation period. This chapter provides an overview of (1) the clinical indications for implantation of prosthetic heart valves; (2) the major types of prostheses and (3) their evaluation using transesophageal echocardiography (TEE); (4) some inherent limitations of echocardiography; and (5) common prosthetic pathology.
Similar to the assessment of native cardiac valves (see Chapters 7, 9, and 10), TEE can provide a detailed evaluation of the structure, function, and integrity of prosthetic valves using two-dimensional (2D), color-flow Doppler (CFD), continuous-wave Doppler (CWD), pulsed-wave Doppler (PWD), and three-dimensional (3D) imaging modalities. However, several features unique to the intraoperative environment such as dynamic changes to preload, myocardial contractility, and afterload can create challenges for the TEE assessment of prosthetic valves. In addition, prosthesis malfunction can affect adjacent valves and chambers, and this must be considered in the assessment. Nevertheless, the integration of information from the TEE examination can provide a comprehensive assessment of the patient's overall cardiac status.
A diseased native valve that is symptomatic will ultimately require intervention (repair or replacement) by percutaneous or surgical means. The most commonly replaced valves are those in the aortic and mitral positions commensurate with the high prevalence of diseases that involve these valves. Recently, with significant improvements in mitral valve repair, the numbers of valves implanted for mitral regurgitation have been decreasing and stenosis has become a more common indication for mitral valve replacement. In addition, with a large number of prosthetic valves already implanted, pathologies involving these replaced valves are increasing the frequency of repeat surgery. Often presenting as new or increased valvular regurgitation in the setting of a systemic infection, endocarditis of the native valve or prosthetic grafts is an infrequent yet important indication for placement of a new prosthesis. In addition, inadequate anticoagulation can lead to acute or chronic stenosis of previously placed valves. The myriad of systemic diseases that can cause valvular dysfunction are comprehensively discussed in the ACC/AHA guidelines for evaluation of patients with valve disease.1
When faced with a patient who needs a valve replacement, cardiologists and cardiac surgeons have a wide variety of valves from a number of manufacturers to select from. The decision as to which prosthesis should be implanted depends on a number of factors including the patient's age, gender (women of child-bearing age), life expectancy, comorbidities, location and size of the diseased valve, surgical expertise or preference, and considerations regarding anticoagulation (noncompliance or likely loss to follow-up).2 A detailed description ...