Importance of Mitral Regurgitation After Isoproterenol Infusion in the Aged

Effects of Isoproterenol (ISP) infusion (0.02μg/kg/min, for 5min.) on the systolic regurgitation murmur, a regurgitant flow and a cardiac index were studied in the non-rhematic mitral regurgitation (MR) in the aged. The group I, whose systolic murmur decreased after ISP, were 16 cases and the group II, whose systolic murmur did not decrease, were 7 cases. We found no differences in the intensity of systolic murmur and cardio-thoracic ratio. Seven cases in the group I had old myocardial infarction but none of the group II had. Electrocardiogram after ISP showed ischemic ST changes in 69.2% of the group I and 50% of the group II. Mitral regurgitant flow estimated by dye dilution method was 48.9% (mean) in the group I and 76.4% in the group II. Cardiac index increased from 2.48l/min/m2 to 3.96l/min/m2 in the group I but did not increase so much in the group II (from 2.38 to 3.37). Decrease of mitral regurgitant flow after ISP was lager in the group I than that in the group II. The difference between stroke volume from echocardiogram and that from dye dilution, which represents mitral regurgitant flow, was smaller (28.4ml) in the group I than that (44.1ml) in the group II. It is suspected that in some cases of mitral regurgitation in the aged mitral regurgitant flow decrease after ISP because of improved left ventricular free wall motion after ISP.