Propranolol-like action of amiodarone. An electronmicroscopic study in rats under cold stress.

The cold stress leads to increased levels of catecholamines, of their precursors and metabolites, with increased oxygen consumption by the myocardium. Atrial cardiomyocytes of amiodarone-treated rats, previously stressed by cold, showed a marked decrease of the morphological alterations observed in the animals submitted to cold stress without amiodarone protection. Such results indicate, at the subcellular level, that amiodarone could improve cardiac function by a propranolol-like action when there is heart failure, a condition in which there is a high level of catecholamine.