Beneficial Effects of Vasodilator Agents in Severe Mitral Regurgitation Due to Dysfunction of Subvalvar Apparatus

To assess the potential beneficial effects of vasodilator agents in patients with severe mitral regurgitation, sodium nitroprusside was administered intravenously at a rate of 16 to 100 μg/min in eight patients with clinically significant mitral regurgitation presumably due to dysfunction of the subvalvar apparatus. In all patients there was a decrease in the magnitude of the peak ‘V’ wave (from 50 ± 4.5 to 19 ± 2.9 mm Hg) and in left ventricular filling pressure (33 ± 1.8 to 16 ± 1.4 mm Hg), together with a decreased intensity of the apical pansystolic murmur. There was a significant increase in forward cardiac index (2.2 ± 3.5 to 3.3 ± .47 liter/min/M2) and forward stroke volume index (23 ± 4.4 to 36 ± 6.6 ml/M2) along with a reduction in systemic vascular resistance (1802 ± 331 to 1102 ± 241 dynes/sec/cm-5). In the five patients in whom the therapy was continued, relief of symptoms of pulmonary venous congestion occurred. In the four patients in whom left ventricular volumes were determined angiographically, the observed increase in forward stroke volume was due to a reduction in the regurgitant fraction. These findings suggest that the use of vasodilator agents like nitroprusside can achieve the major objectives of treatment of patients with mitral regurgitation: an increase in forward stroke output, a reduction in regurgitant volume and a decrease in pulmonary venous pressure.