Use of radionuclide ventriculography for assessment of changes in myocardial performance induced by disopyramide phosphate.

Disopyramide phosphate may precipitate heart failure in susceptible patients with cardiomegaly. To identify those at risk, gated radionuclide ventriculography (RVG) was performed in two groups. Eleven patients without evidence of structural heart disease constituted group 1, and 12 with impaired ventricular function made up group 2. RVG was carried out before and 2 hours after administration of a single 300-mg dose of disopyramide orally. After disopyramide mean left ventricular ejection fraction (EF) decreased in the 12 patients in group 2 (35% to 26%) (p less than 0.01); depression of function was most pronounced in regions with the poorest baseline value. Of the 11 patients in group 1 (mean EF 60%), EF was reduced after disopyramide in only one. Serum levels of drugs were comparable in patients in both groups (3.1 vs. 3.7 micrograms/ml). We conclude that (1) patients with left ventricular dysfunction are particularly susceptible to the depressant effects of disopyramide; (2) RVG is a sensitive technique for detecting disopyramide-induced changes in ventricular performance; and (3) RVG before and shortly after a dose of disopyramide orally may help to identify those patients at high risk.