Transient atrioventricular block after release of aortic cross-clamp

To determine the incidence of atrioventricular (A-V) block, 86 patients, aged 58.9 +/- 10.4 yr, undergoing elective coronary artery bypass grafting (CABG) during aortic cross-clamping (ACC) and cold potassium cardioplegia were investigated. The incidence and duration of complete A-V block after release of the aortic cross-clamp was monitored. Twenty-four percent of the patients developed complete A-V block that required temporary pacing for a mean time of 66 +/- 39 min. The volume of cardioplegia used was not significantly different between the patients who developed A-V block and the patients who had no block. The serum potassium level at the time of release of the aortic cross-clamp was within the normal range in both groups. Six factors were correlated with the development of A-V block: old age, preparation by a combination of beta-adrenergic blockers and calcium channel blockers, preoperative bradycardia, the number of vessels grafted, as well as the duration of ACC. Also, the serum potassium level at the time of release of the aortic cross-clamp was significantly higher in the patients who developed A-V block. The high incidence of A-V block in elderly patients undergoing multiple coronary vessel grafting during a prolonged ACC time suggests that suboptimal myocardial preservation may be the main predisposing factor.