Preoperative evaluation of patients with electrocardiographic conduction defects.

Prophylactic pacemakers should be recommended for all preoperative patients with second- and third-degree heart block, regardless of whether the block is in the AV node or the trifascicular conduction system. Symptomatic patients with potential for trifascicular block should also have a transvenous pacemaker. Those without symptoms should be monitored during anesthesia and the postoperative recovery period.