Abstract
The effects of therapeutic doses of antiarrhythmic drugs (12 mg/Kg of procainamide, 2 mg/Kg of disopyramide and 0.2 mg/Kg of propranolol) on sinus cycle length (SCL), sinoatrial conduction time (SACT) estimated by a constant atrial pacing technique, and atrial developed tension (DT) were measured in isolated canine atria cross-perfused with heparinized arterial blood from donor dogs as well as on mean systemic blood pressure (SBP) and on heart rate (HR) in those dogs. Procainamide, which produced hypotension and bradycardia in the donor dog, did not change SACT significantly, although it increased SCL and decreased DT in the isolated atrium. However, disopyramide raising SBP slightly (but not significantly) and decreasing HR in the donor dog produced a significant prolongation of SACT and SCL and reduction of DT in the isolated atrium. Propranolol caused slight but insignificant hypotension and long-lasting bradycardia in the donor dog, accompanied by a significant increase in SCL and SACT, and decrease in DT in the isolated canine atrium. We concluded that SACT was significantly increased by a therapeutic dose of propranolol and disopyramide but was not altered by that of procainamide.
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