Effects of papaverine upon ectopic ventricular tachycardia produced by myocardial infarction.

LIGATION of the anterior descending artery of the dog's heart by a standard technic produces ectopic ventricular tachycardia after a delay of four and onie-half to eight hours. Untreated, the tachycardia continues two to four days and there may be some ectopic beats on the fifth day. This persistent ectopic ventricular tachycardia that develops with myocardial infarction is difficult to suppress with drugs, and the standardization of the method has provided an exacting test preparation. 34 It has been shown by other investigators that papaverine raises the fibrillation threshold (intimately related to threshold for premature systoles) of the dog's ventricles to brief direct current stimuli5 and reduces the excitability of the dog's auricles to faradic stimuli.6 The excised papillary muscle of the cat exhibited increased excitability to induction shocks when treated with papaverine in concentrations below 4.5 X 10-2 mmol., and excitability was reduced by higher concentrations. Automaticity was induced by the higher concentrations, generally within the range that diminished excitability to shocks.7 Papaverine has been reported effective in abolishing auricular and