Clinical application of ultrasound in the analysis of prosthetic ball valve function^*

The ultrasonic pulse reflection technic provides a means of recording time-displacement curves of prosthetic ball or cage motion which closely correlate with similar time-displacement curves plotted from cinefluorographic film. Precise correlation with events recorded by phonocardiogram, electrocardiogram, apex cardiogram and pressure curves is easily accomplished. Prosthetic aortic and mitral balls maintain normal timing characteristics with the apex cardiogram when compared with normal aortic and mitral valves, but the contour of mitral prosthetic ball motion resembles that of mitral stenosis. This is thought to be the result of the flow characteristics through a prosthetic valve rather than a representation of true stenosis. Opening and closing of these valves is clearly related to appropriate crossover pressure changes. The origin of systolic clicks from aortic prostheses and diastolic clicks from mitral prostheses appears related to bounces or vibratory motion at the apex of the respective cages. Cage motion reflects motion of the ring to which the valve is anchored. Thus, considerable motion of the mitral cage reflecting motion of the atrioventricular ring is normal, but only slight motion of the aortic ring is seen. Precise timing of the balls of multiple valve replacement with relation to each other may be obtained by modification of existing instrumentation to permit the recording of more than one signal. The velocity of the opening and the closing ball within a cage may be obtained by direct measurement of slope or, perhaps more accurately, by electronic recording of the first derivative of displacement in relation to time. Mitral ball closing velocity is nearly double opening velocity. Aortic ball closing velocity slightly exceeds opening velocity by direct measurement. Observations on ball velocity may provide information on valvular function if studied over a long period of time.