RESUMEN
Two-hundred-fifty-eight patients who had cardiac surgery with extracorporeal circulation were studied to determine the frequency and significance of conduction disturbances. Fifty-eight (34%) developed new postoperative conduction defects. Seventeen patients developed new conduction alterations after coronary artery bypass graft. The most common disturbance was transient bifascicular block (right bundle branch block and anterior subdivision block of the left bundle branch of His) (p less than 0.01). After valvular surgery twenty-one patients developed conduction defects. Of those the most common disturbance was high degree AV block (57%). The authors found no relation between the AV block and the number of valves operated on or type of valvular surgery. After congenital heart surgery, twenty patients developed conduction defects. The most common defect was high degree AV block. The frequency of complete heart block was higher after the closure of atrial septal defects (P less than 0.01). None of the conduction defects were related to the amount of time the patient was exposed to extracorporeal circulation or to postoperative myocardial infarction. All conduction defects were transient except complete heart block in some patients with ventricular septal defect surgery. In this study there were no hemodynamic complications or mortality associated with the conduction disturbances.