Effectiveness of nupercaine hydrochloride and phenobarbital sodium in the suppression of ventricular tachycardia associated with acute myocardial infarction.

In 22 dogs with ventricular tachycardia accompanying myocardial infarction, Nupercaine hydro-chloride was found to be a potent suppressor of ectopic impulses. When used alone Nupercaine also produced vomiting and convulsive movements. When combined with morphine, vomiting was eliminated , but convulsions still occurred. When combined with phenobarbital sodium or pentobarbital sodium, the ectopic impulse suppressor action of Nupercaine was enhanced and both vomiting and convulsive movements were prevented. The duration of ectopic impulse suppressor action was significantly greater in the phenobarbital-Nupercaine experiments than in any other group. No deaths occurred. THE DEMONSTRATION by Mautz in 19361 that procaine, Metycaine and cocaine, locally applied, significantly increase the electrical threshold of heart muscle for premature systoles was followed by the widespread application of procaine as a protective agent in cardiac surgery. The studies of Mautz also initiated investigations designed to test the effectiveness of procaine in the prevention or suppression of cardiac arrhythmias of other origins. The experimental arrhythmias usually were produced in animals by the administration of epinephrine after sensitization with chloroform or cyclopropane. Some authors reported that procaine was effective in preventing ventricular tachycardia and fibrillation which commonly resulted from these procedures,2-5 but Huggins and co-work-ers6 found that the effects of procaine were too fleeting to be of practical value.6 Zapata-Diaz and co-workers7 terminated auricular paroxys-mal tachycardia and ventricular premature systoles in a few cases by intravenous procaine, but failed in other cases of auricular paroxysmal tachycardia, auricular fibrillation, and ventricu-lar tachycardia. Recently, procaine amide (Pronestyl), which is removed from the blood slowly, and which therefore has a prolonged duration of action, has been found more effective in preventing epinephrine-induced arrhythmias in animals and in the treatment of certain types of ar-rhythmias in patients.8' 9 Procaine amide has been only partially successful in the prophy-laxis and therapy of cardiac arrhythmias during thoracic surgery'0 and in the treatment of supraventricular arrhythmias." It has produced distressing toxic reactions including paroxysms of ventricular tachycardia." The development of a standard technic for producing ventricular tachycardias associated with myocardial infarction in dogs has provided an experimental preparation which reproduces in many important features this grave type of arrhythmia in man.'2-'4 A high frequency ectopic ventricular tachycardia produced by myocardial infarction often has been found difficult to control with drugs most commonly used clinically for this purpose ,'3 14 therefore the use of such an experimental preparation provides a severe test for the drug being studied. …