A comparison of tests for antifibrillatory action.

THE OBJECT OF THE EXPERIMENTS WAS TWOFOLD: first, to choose the most satisfactory test for antifibrillatory action; secondly, to place several drugs with reputed antifibrillatory activity in an order of potency as a preliminary to investigating their mode of action. Measurements were made on isolated rabbit atria at 34 degrees C of (1) the maximum driving frequency the atria would follow, (2) conduction velocity, (3) contractions, and of the threshold for the production of (4) extrasystoles, (5) flutter and (6) fibrillation. Log dose-response curves were plotted for quinidine, papaverine, procaine, dibenamine and procaine amide. The maximum frequency test and fibrillation threshold test gave similar results with all the drugs, and the results gave the order quinidine 1.0, procaine 0.53, Dibenamine 0.47, papaverine 0.43 and procainamide 0.26. Thresholds for extrasystoles and flutter were much more variable. The regressions relating changes in conduction velocity and contraction to log dose were different from those for maximum driving frequency and fibrillation threshold for procaine, papaverine and dibenamine, but the regressions for quinidine and procaine amide were nearly parallel in all tests. Serpajmaline contained a substance with antifibrillatory activity as great as that of quinidine and with no greater depressant action on contractions.