Atrioventricular pressure half-time. Measure of mitral valve orifice area.

In 20 patients studied by cardiac catheterization, the time required for the diastolic left atrioventricular pressure difference to fall to half its initial value (half-time) varied with the anatomic severity of the valvular stenosis. In mild mitral stenosis, the half-time was approximately 100 msec; in moderate stenosis, it was about 200 msec; and it was 300 msec or longer in severe stenosis. The half-time at the nonstenotic mitral valve was less than 25 msec. Although exercise increased the atrioventricular pressure gradient, heart rate, and cardiac output significantly, the half-time was affected only slightly. Mitral regurgitation of various severities did not affect the half-time. The half-time appears to vary inversely with the anatomic orifice area of the mitral valve. The determination of the half-time obviates the need for the commonly used exercise test for the evaluation of mitral stenosis.