A comparison of the effects of quinetholate, lidocaine and procainamide on ouabain-induced ventricular tachycardia and cardiac function.

The antiarrhythmic effects of the quinoline derivative, quinetholate, on ouabain-induced tachycardia were compared with those of lidocaine and procainamide in dogs. In addition, the effects of these three agents on cardiac function were compared. Quabain was injected intravenously until ventricular ectopic beats accounted for at least 60% of the heart rate. Then one of the above antiarrhythmic agents was infused until sinus rhythm was reestablished for a minimum of 3 min or until it became evident that successful reversion would not occur. All three agents effectively reversed ouabain-induced ventricular tachycardia in most instances. Quinetholate was especially consistent, causing 16 reversions out of a total of 17 experiments. The relative molar antiarrhythmic potencies of the three agents in responding animals were as follows: lidocaine = 1.0, procainamide = 1.5, and quinetholate = 3.1. Quinetholate caused the longest lasting reversions, i.e. usually lasting at least 30 min after infusion was stopped. The degree of cardiac depression caused by the three agents at their mean effective antiarrhythmic doses was determined using the left ventricular function curve method. Lidocaine produced a significant depression of the ventricular function curve at the antiarrhythmic dose while procainamide and quinetholate did not.