Cardiac transplantation does not effect ischaemia-induced arrhythmias in rats

Objective: In many species arrhythmias induced by myocardial ischaemia appe ar to be in part dependent upon cardiac sympathetic nerves. However, previo us experiments in rats did not suggest that myocardial or other catecholami nes are involved in ischaemic arrhythmogenesis in this species. The aim of this study was to investigate this further using transplanted hearts, Metho ds: We transplanted 'donated' hearts onto the abdominal aorta of recipient rats and, at varying periods after transplantation, subjected donated and r ecipient hearts to occlusion of the left anterior descending (LAD) coronary artery. Donated and recipient hearts were tested at various times after tr ansplantation for responsiveness to drugs acting upon aspects of the autono mic nervous system. The intention of this latter study was to assess the st atus of innervation and receptors simultaneously in both donated and recipi ent hearts. Results: Donated (transplanted) hearts showed responses consist ent with denervation and receptor supersensitivity. Changes varied with the duration of the transplant. Over the same period recipient hearts did not change in responsiveness to drugs. When subjected to coronary artery occlus ion, transplanted hearts responded to occlusion with the same frequency and severity of arrhythmias as recipient and other control hearts, regardless of the duration of transplant, or sensitivity to drugs. Conclusions: The re sults of these experiments suggest that cardiac innervation is not an impor tant factor in the genesis of ischaemia-induced arrhythmias in rats. (C) 19 99 Elsevier Science B.V. All rights reserved.