Prevention by dexamethasone of the marked antiarrhythmic effects of preconditioning induced 20 h after rapid cardiac pacing

Abstract

Dogs were paced, via a pacing electrode in the right ventricle, for four 5 min periods at a rate of 220 beats min−1. On the following day they were reanaesthetized, thoracotomized and the left anterior descending coronary artery occluded for 25 min. Pacing markedly reduced the severity of ischaemia‐induced arrhythmias (e.g. reduction in VF from 45% in unpaced dogs to 10% in paced dogs; P < 0.05), an effect reversed by dexamethasone (4 mg kg−1 i.v., 45 min prior to pacing). This protection may be due to the induction of nitric oxide synthase or cyclo‐oxygenase. 1994 British Pharmacological Society