Doppler Evidence for Reduced Atrial Contribution to Left Ventricular Filling in Patients with a Dilated Cardiomyopathy and a 'B-Bump' on the Mitral Valve Echocardiogram

Abstract

The hemodynamic contribution of left atrial contraction to left ventricular filling in dilated cardiomyopathy (DCM) remains controversial. The degree of filling of the left ventricle may influence this contribution. Previous studies have demonstrated a correlation between an elevated left ventricular enddiastolic pressure (LVEDP) and the presence of a ‘B-bump’ (a deflection on the A-C closure slope) on the anterior mitral valve leaflet on the M-mode echocardiogram. To assess whether the presence of a ‘B-bump’ reflecting an elevated LVEDP is associated with differences in left atrial contribution to left ventricular filling, we measured pulsed-wave Doppler mitral flow velocity recordings obtained from 48 DCM patients, with (n = 16) and without (n = 32) a ‘B-bump’. There were no statistically significant differences between the two groups with regard to age, heart rate, body surface area, electrocardiographic PR interval, left ventricular end-diastolic dimenson, left ventricular percent fractional shortening, left atrial size, or distance of penetration of the mitral regurgitant signal into left atrium. The mean ratio of mitral peak-signal velocity in late-to-early diastole, PFVA/PFVE (0.58 ± 0.24 in those with ‘B-bump’ versus 0.96 ± 0.55 in those without a ‘B-bump’, p < 0.005, and the mean ratio of time-velocity integral in late-to-early diastole 0.39 ± 0.14 vs. 0.65 ± 0.34, p < 0.002) were both found significantly decreased in the ‘B-bump’ group. Since the mitral time-velocity integral is proportional to stroke volume, and the A/E integral ratio approximates a volume ratio of transmitral flow, it is concluded that in the group of patients with DCM and a ‘B-bump’ of the anterior mitral leaflet, corresponding to an elevated LVEDP, the relative left atrial volume contribution to left ventricular filling and stroke volume is reduced.