[Experimental anti-arrhythmic effects of a new beta-adrenergic receptor blocking agent, dl-l-(tert. butylamino)-3-[(2-propinyloxy)phenoxy]2-propanol hydrochloride (dl Kö 1400-Cl)].

Antiarrhythmic property of a new adrenergic beta-blocking agent, dl-1-(tert.butylamino)-3[(2-propinyloxy) phenoxy]-2-propanol hydrochloride (Kö 1400-Cl) was studied, using 1) ouabain-induced arrhythmia in the guinea pig, 2) aconitine-induced arrhythmia in the rat, 3) arrhythmia induced by two-step ligation of coronary artery (Harris's method) in the dog and 4) halothane-adrenaline arrhythmia in the dog and was compared with those of propranolol, oxprenolol, procainamide and ajmaline. Procainamide and ajmaline produced a marked protective effect against aconitine-induced ventricular extrasystole, but were not so effective against aconitine-induced ventricular fibrillation, while oxprenolol and, to a lesser degree, propranolol were effective against the latter type of aconitine arrhythmias. Kö 1400-Cl proved to be ineffective. All the compounds tested produced a marked protective action against ouabain-arrhythmia. Whereas procainamide was most effective in abolishing the ventricular arrhythmia due to coronary-ligation even on the first postoperative day, Kö 1400-Cl and propranolol were almost ineffective on the first day. Even on the second postoperative day, the antiarrhythmic effects of these two beta-blockers were not remarkable, effective only in 2/4 animals in the case of Kö 1400-Cl and in 2/3 animals in the case of propranolol. On the contrary, all the beta-blockers tested produced a protective action against halothane-adrenaline arrhythmia at much lower doses than against coronary ligation arrhythmia. The potency ratio of Kö 1400-Cl and propranolol was 3 : 1, which paralleled with beta-blocking activity of these compounds.