[Experimental studies of the hemodynamics of disopyramide in comparison with quinidine]

The haemodynamic effects of quinidine and disopyramide i.v. were investigated in 79 rats. Measurements were performed in the intact circulation (LVP, AoP, dp/dtmax). Myocardial function was examined independently of circulatory changes by isovolumetric registrations (peak LVP). Animals with NaCl infusion served as controls. After infusion of 5 mg/kg (10 mg/kg) quinidine, we obtained a reduction (p less than 0.05) in the left ventricular pressure to 81.6 +/- 3.1% (82.6 +/- 3.7%), in the mean aortic pressure to 70.7 +/- 3.4% (79.3 +/- 6.7%), in dp/dtmax to 73.9 +/- 5.6% (72.8 +/- 6.2%), and in the heart rate to 69.7 +/- 7.4% (69.9 +/- 5.4%). Isovolumic pressure maxima after quinidine were not different from the controls (90.7 +/- 2.4% and 93.6 +/- 1.5% respectively vs. 96.1 +/- 1.0%). 1 mg/kg disopyramide caused no significant haemodynamic changes. 2 mg/kg disopyramide led to a slight increase in dp/dtmax (107.2 +/- 5.6%, N.S.), while 4 mg/kg disopyramide had a tendency to reduce the left ventricular pressure (88.5 +/- 6.2%), mean aortic pressure (80.5 +/- 14.8%) and dp/dtmax (75.1 +/- 8.0%). After 4 mg/kg disopyramide, the isovolumic maxima were reduced. Our results indicate that the haemodynamic side effects of class-I antiarrhythmic drugs are different. Quinidine i.v. caused a reduction in pressures and heart rate, but had no influence on the isovolumic pressure maxima. Disopyramide i.v., on the other hand, had no significant haemodynamic effects in clinical doses. After high (not clinically used) doses of disopyramide (4 mg/kg), which also led to high plasma levels, myocardial performance was depressed.(ABSTRACT TRUNCATED AT 250 WORDS)