Influence of antiarrhythmic agents on calcium-induced cardiac arrhythmias in the rat.

IT has been well established that calcium can produce various alterations in cardiac rhythm such as fibrillation, arrest and/or bradycardia." Recently, Malinow presented a standardized method for producing ventricular fibrillation in the rat by calcium injection. This method was employed in the present study to evaluate a series of anti-arrhythmic compounds which were previously found effective in the treatment of several atrial and ventricular arrhythmias in the dog. During the present studies it was observed that when fibrillation was prevented other effects of calcium, particularly cardiac arrest, appeared. This report describes the effect of these compounds on calcium-induced alterations of cardiac rhythm. The compounds* studied include quinidine and procaine amide in addition to SC-3920, N-(7-isopropylaminopropyl)-a, a-diphenylacetamide hydrochloride; SC-3323, /Sdiisopropylaminoethyl 4 phenyl 4 tetrahyd ropy rancarboxy late hydrochloride; SC3755, O-(4-chlorobenzyl)phenoxyacetamidine hydrochloride; SC-2919, N,X,N'-triphenylN'-(j8-diethylaminoethyl)urea hydrochloride; and SC-3412, /9-diethylaminoethyl-2,6-dimethyl -5,6 dihydro -4 H pyran 3carboxy late hydrochloride.