Normal Myocardial Contractile State in the Presence of Quinidine

SUMMARY Since quinidine is one of the few agents available to treat and prevent ventricular arrhythmias in am-bulatory patients, its hemodynamic effects have been re-evaluated. When given in therapeutic doses to anesthetized mongrel dogs, quinidine significantly reduced heart rate, aortic pressure and flow, but it did not significantly change the first derivative of the left ventricular pressure curve (left ventricular dp/dt) in nine dogs. A subsequent group of dogs was studied after vagotomy and practolol administration to block cardiac reflexes. This group showed significant reduc-tions in heart rate, aortic pressure and left ventricular dp/dt, OQUINIDINE is widely used to treat and prevent cardiac arrhythmias, and its hemodynamic effects have been studied extensively. However, the effects of this agent on myocardial contractility remain controversial. Experiments in isolate