Dynamic mitral regurgitation. An important determinant of the hemodynamic response to load alterations and inotropic therapy in severe heart failure

Abstract

Cardiac performance and mitral regurgitation were measured by Doppler echocardiography and right heart catheterization in 12 patients with severe congestive heart failure who performed isometric exercise during control and intravenous administration of dobutamine and nitroglycerin. During control isometric exercise, mitral regurgitant volume increased from 18 ± 13 to 31 ± 17 ml (p < 0.01), while forward stroke volume, by both thermodilution and Doppler echocardiography, substantially decreased. At rest, dobutamine decreased mitral regurgitant volume from 18 ± 13 to 11 ± 10 ml (p < 0.05), while forward stroke volume increased from 46 ± 13 to 55 ± 15 ml (p < 0.05). During isometric exercise, dobutamine tended to decrease mitral regurgitant volume (24 ± 12 vs. 31 ± 17 ml; NS) when compared with control exercise. At rest, nitroglycerin decreased mitral regurgitant volume from 18 ± 13 to 11 ± 11 ml (p < 0.05), while forward stroke volume, by both thermodilution and Doppler echocardiography, substantially increased. Similarly, during isometric exercise, nitroglycerin decreased mitral regurgitant volume from 31 ± 17 to 20 ± 14 ml (p < 0.05), while significantly increasing forward stroke volume. At control rest, the median mitral regurgitant fraction was 24% for the 12 patients. Neither dobutamine nor nitroglycerin changed significantly forward stroke and mitral regurgitant volumes at rest and during isometric exercise in the six patients with resting mitral regurgitant fraction below the median. In contrast, dobutamine and nitroglycerin significantly decreased mitral regurgitant volume and increased forward stroke volume both at rest and during isometric exercise in the six patients with mitral regurgitant fraction greater than the median. Thus, aggravation of mitral regurgitation contributes substantially to the fall in forward stroke volume noted during isometric exercise in patients with severe congestive heart failure. The presence and severity of functional mitral regurgitation appears to be an important determinant of the hemodynamic response to acute therapy with dobutamine and nitroglycerin in these patients.