Echokardiografische Pitfalls bei Herzklappenerkrankungen

Abstract

Cardiac ultrasound and clinical evaluation form the basis of clinical decision making in patients with valvular heart disease. Indication to perform cardiac catheterization and indication fpr surgery largely depend on clinical and echocardiographic findings. Although rapid development of technology contributes significantly to the robustness of ultrasound measurements one has to consider that echocardiography is an observer dependend and thus subjective method. This review focusses on potential pitfalls in image acquisition and interpretation of echocardiographic findings in acquired valvular heart disease. Machine settings have to be tailored to the individual patient very carefully to maximize image quality and color Doppler signals in order to judge chamber and valve geometry and function. A key issue in asymptomatic severe regurgitant lesions is not to miss worsening of left ventricular function. Thus serial evaluation of left ventricular dimensions and ejection fraction help to assess ventricular function. For quantification of LV ejection fraction the modified Simpson’s rule is standard and Teicholz formula is obsolete. Yet, EF is load dependent and newer parameters derived from deformation imaging (strain and strain rate) give a better understanding of ventricular contractility but are currently not part of guidelines. Left heart contrast agents can contribute to better endocardial border delineation in difficult to image patients. Aortic stenosis ist the most common lesion in adults that requires surgical treatment. The most robust parameter to judge severity is valve area based on continuity equation (severe when < 0,75 cm 2 ) or direct planimetry by TEE (severe when < 1,0 cm 2 ). A pitfall is to report valve gradient alone, specifically in impaired LV function where low gradients may be misleading. Dobutamine stress echo may help identify critical low gradient low output aortic stenosis. Even in preserved LV functrion gradients may be low when total arterial compliance is low and there is severe LV hypertrophy in small ventricles. Evaluation of mitral regurgitation should rely on the synopsis of several parameters such as vena contracta and if possible calculation of effective regurgitant orifice area using the PISA method. Jet dimensions largely depend on arterial blood pressure and can be misleading. In asymptomatic patients worsening of LV function, ventricular enlargement and endsystolic LV dimesions ≥ 45 mm should lead to plan surgery. Aortic regurgitation also mandates close monitoring of ventricular dimesions when judged severe by vena contracta in asymptomatic patients (LVEDD ≥ 70 mm, EF < 50 % or LVESD ≥ 50 mm are accepted cut off limits to consider surgery). Doppler parameters such as pressure half time or deceleration rate can be confounded by ventricular pathology influencing filling pressures. Since in severe regurgitant lesions as well as in severe mitral and aortic stenosis the indication for surgery is usually clear in symptomatic patients it is a challenge to assess symptomatic state in patients in routine practice. Especially elderly patients usually adapt to their physical limitation and tend to report to be symptom free when asked by the physician. Such asymptomatic” conditions should be objectified by subjecting the patient to careful exercise. Not to objectify an asymptomatic state may be the greatest pitfall in evaluating patients with valvular heart disease. Future results in ongoing studies may clarify the impact of deformation imaging to detect progressive impairment in ventricular function.