Effects of isosorbide dinitrate on rheumatic and non-rheumatic mitral regurgitation

Isosorbide dinitrate was given to seven patients with isolated mitral regurgitation (three cases of rheumatic origin, four non-rheumatic) to assess its hemodynamic effects. The pulmonary capillary pressure, left ventricular end-diastolic pressure, left ventricular end-diastolic volume index, and the aortic pressure were all significantly reduced. The heart rate was significantly increased, while the systemic vascular resistance and the left ventricular contractility index were unchanged. The regurgitant flow increased by an average of 72.2% in the rheumatic group, but decreased by an average of 4.8% in the non-rheumatic group (p < 0.05). The forward cardiac output decreased slightly in both groups, but the difference was not significant (NS). It appears that isosorbide dinitrate has a more detrimental effect on cases of mitral regurgitation of rheumatic origin than on those of non-rheumatic origin. We suggest the difference in the responses is a consequence of the dynamic nature of the regurgitant orifice in the non-rheumatic group and the static nature of the orifice in the rheumatic group.