Effects of atrial natriuretic peptide on ischaemia-induced arrhythmias in the rat heart: arrhythmogen or endogenous antiarrhythmic agent?

Myocardial infarction and heart failure are associated with an elevation in plasma levels of atrial natriuretic peptide (ANP). The early stages of myocardial ischaemia and infarction are associated with serious ventricular arrhythmias. We examined the possibility that ANP may function in early ischaemia to alter the susceptibility of the heart to arrhythmias by perfusing rat hearts (n = 12 in each group) with various concentrations of ANP during periods of aerobic perfusion and regional ischaemia. The complications associated with the release of endogenous ANP were precluded by carrying out the experiments with an isolated Langendorff (nonrecirculating) preparation in which the atrial effluent does not gain access to the ventricular coronary arteries. When compared with control hearts, ANP (0.02, 0.2, 0.6, or 2.0 nM) had no significant influence on the ventricular arrhythmias (ventricular premature beats, tachycardia, and fibrillation) elicited by 30-min regional myocardial ischaemia. Heart rate and coronary flow were also unchanged. We conclude that in the isolated rat heart during myocardial ischaemia ANP probably has no significant mediatory or modulatory role in the pathogenesis of serious ventricular arrhythmias.