Effects of four antiarrhythmic drugs on sino-atrial conduction time in isolated, blood-perfused dog atria

Abstract

We examined effects of four antiarrhythmic drugs (quinidine, disopyramide, procainamide and propranolol) on sinus cycle length (SCL), sino-atrial conduction time (SACT) measured by a constant atrial pacing technique, and developed tension (DT), using isolated dog atrial preparations perfused with blood from anesthetized donor dogs. Control SCL and SACT were 600-700 msec and 60-70 msec, respectively. When quinidine, disopyramide and procainamide were continuously infused into the sinus node artery at rates of 10-40 ug/min and propranolol was infused at a rate of 1-4 pg/min, all 4 agents prolonged SCL and SACT and reduced DT dose-dependently. At higher doses quinidine and disopyramide tended to prolong SACT more than procainamide and propranolol. When 2 mg/kg of quinidine, disopyramide and procainamide and 0.2 mg/kg of propranolol were given i.v. to the donor dog, all the drugs except procainamide prolonged SCL, but only propranolol lengthened SACT in the isolated atrium. Our results indicate that these four antiarrhythmics cause a dose-related increase on SCL and SACT and decrease in DT, and propranolol is 10 times as potent as the other agents in negative chrono-, dromo- and inotropisms.