Exercise Evaluation of Prosthetic Heart Valves by Doppler Echocardiography: Comparison with Catheterization Studies

Although valve replacement remains the cornerstone of treatment for critical heart valve dysfunction, problems including thromboembolism, infection, and primary failure of the prosthesis remain. Resting studies of valve hemodynamics are sometimes insufficient to reveal valve dysfunction. Early studies using cardiac catheterization focused on changes in prosthetic function seen with various types of exercise or drug‐induced stress. These studies suffered from an inability to adequately stress catheterized patients and were cumbersome to the patient and the investigator. With the introduction of Doppler echocardiography, however, studies could be performed after significant exercise with low risk and increased ease. Using echocardiography, reports of exercise‐induced changes in aortic and mitral valve hemodynamics have appeared. Over 600 patients have been studied using Doppler echocardiography. In the aortic position, all prostheses studied have a mild peak instantaneous gradient (18–26 mmHg) at rest, which increases with exercise (35–63 mmHg). No significant differences between the four models of mechanical prostheses studied are found. The gradients achieved with exercise do not appear to be related to the heart rate achieved or duration of exercise. Smaller prostheses are associated with larger gradients; however, the correlation was not strong. All mitral valve prostheses studied are also mildly stenotic at rest (range of mean gradients 2.3–7.1 mmHg) and become moderately stenotic with exercise (range 5.1–16.5). Although the lowest gradients are seen with St. Jude Medical and Medtronic Hall prostheses, their gradients are not significantly less than with other valves. Exercise duration and heart rate attained are not correlated to gradient, and valve size is not related to gradient except in the case of the larger St. Jude Medical valves. Other factors predictive of low levels of exercise tolerance are age >50 and predominant mitral regurgitation before replacement. In summary, exercise Doppler echocardiography offers a noninvasive technique to evaluate prosthetic heart valves. It is reproducible, safe, and less cumbersome than cardiac catheterization. A range of normal exercise hemodynamics has been established for aortic and mitral prostheses. Using these parameters, the diagnosis of early prosthetic dysfunction can be made.