Heart block after coronary artery bypass--effect of chronic administration of calcium-entry blockers and beta-blockers.

We evaluated risk of heart block after cardiopulmonary by-pass (CPB) in patients with normal conduction undergoing coronary artery bypass grafting who chronically received calcium-entry blockers, beta-blockers, or combined therapy. Before CPB, calcium-entry blockers alone produced an increase in P-R intervals but no change in heart rate; calcium-entry blocker effects were undetectable after CPB, beta-Blockers alone or with calcium-entry blockers produced lower heart rates and longer P-R intervals throughout the entire perioperative period when compared to no therapy (control) or calcium-entry blockers alone. Complete heart block did not occur; one control patient had transient second degree block after CPB. First degree block appeared transiently in 5% of the patients after anesthetic induction and in 15% on emergence from CPB, but was unrelated to drug therapy. We conclude that chronic calcium-entry blocker therapy has minimal effects on conduction perioperatively; beta-blocker effects persist for up to 10 hr after CPB; and the risk of heart block with either drug or combination is low and should not be a factor in their continued administration preoperatively.