Key result
Propranolol prolonged A-V conduction time and FRP, pindolol had virtually no effect except at high doses, and carteolol shortened them at high doses in open-chest dogs.
Why the study?
Does intravenous administration of propranolol, pindolol, or carteolol affect atrio-ventricular conduction time and functional refractory period in open-chest dogs?
Does intravenous administration of propranolol, pindolol, or carteolol affect atrio-ventricular conduction time and functional refractory period in open-chest dogs?
Different beta-blockers exhibit distinct electrophysiological profiles on AV conduction in dogs, driven by varying degrees of sympathomimetic and non-specific depressant actions.
Animal data on beta-blocker effects on AV conduction are hypothesis-generating; human studies needed before clinical translation.
In open-chest dogs the heart rate was controlled at 150 beats/min and drugs were given intravenously. Propranolol (30 microgram/kg--1 mg/kg) prolonged the atrioventricular (A-V) conduction time and functional refractory period of the A-V conduction system (FRP) by blockade of the existing tone of the sympathetic nerves to the heart. The prolongation of the two parameters by the non-specific depressant action of propranolol was evident only at 3 mg/kg. Propranolol (3--30 microgram/kg) shortened the A-V conduction time in the heart deprived of the vagal and sympathetic tone, suggesting some sort of sympathomimetic effect. Pindolol in a wide range of doses (0.3--300 microgram/kg) exerted virtually no effect on the A-V conduction time and FRP, and its non-specific depressant action was apparent only at 3 mg/kg. Carteolol slightly prolonged the A-V conduction time and FRP only in low doses (1--10 microgram/kg), and in high doses (30 microgram/kg--1 mg/kg) it shortened the two parameters, reflecting its predominant sympathomimetic action.
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Taira et al. (1978) studied Open-chest dogs. Propranolol, Pindolol, and Carteolol was evaluated on Atrioventricular (A-V) conduction time and functional refractory period of the A-V conduction system (FRP). Propranolol prolonged A-V conduction time and FRP, pindolol had virtually no effect except at high doses, and carteolol shortened them at high doses in open-chest dogs.
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