Atrioventricular block in coronary artery bypass surgery: perioperative predictors and impact on mortality

Introduction

Disturbances of the cardiac conduction system are frequent in thepostoperative period of coronary artery bypass surgery. They are mostlyreversible and associated with some injury of the conduction tissue, causedby the ischemic heart disease itself or by perioperative factors.

Objective

Primary: investigate the association between perioperative factors and theemergence of atrioventricular block in the postoperative period of coronaryartery bypass surgery. Secondary: determine the need for temporary pacingand of a permanent pacemaker in the postoperative period of coronary arterybypass surgery and the impact on hospital stay and hospital mortality.

Methods

Analysis of a retrospective cohort of patients submitted to coronary arterybypass surgery from the database of the Postoperative Heart Surgery Unit ofthe Sao Lucas Hospital of the Pontifical Catholic University of Rio Grandedo Sul, using the logistic regression method.

Results

In the period from January 1996 to December 2012, 3532 coronary artery bypasssurgery were carried out. Two hundred and eighty-eight (8.15% of the totalsample) patients had atrioventricular block during the postoperative periodof coronary artery bypass surgery, requiring temporary pacing. Eight ofthose who had atrioventricular block progressed to implantation of apermanent pacemaker (0.23% of the total sample). Multivariate analysisrevealed a significant association of atrioventricular block with age above60 years (OR=2.34; CI 95% 1.75-3.12; P<0.0001), female gender (OR=1.37;CI 95% 1.06-1.77; P=0.015), chronic kidney disease (OR=2.05; CI 95%1.49-2.81; P<0.0001), atrial fibrillation (OR=2.06; CI 95% 1.16-3.66;P=0.014), functional class III and IV of the New York Heart Association(OR=1.43; CI 95% 1.03-1.98; P=0.031), perioperative acute myocardialinfarction (OR=1.70; CI 95% 1.26-2.29; P<0.0001) and with the use of theintra-aortic balloon in the postoperative period of coronary artery bypasssurgery (OR=1.92; CI 95% 1.21-3.05; P=0.006). The presence ofatrioventricular block resulted in a significant increase in mortality(17.9% vs. 7.3% in those who did not develop atrioventricular block)(OR=2.09; CI 95% 1.46-2.99; P<0.0001) and a longer hospital stay (12.75days x 10.53 days for those who didn''t develop atrioventricular block)(OR=1.01; CI 95% 1.00-1.02; P=0.01).

Conclusions

In most cases, atrioventricular block in the postoperative period of coronaryartery bypass surgery is transient and associated with several perioperativefactors: age above 60 years, female sex, chronic kidney disease, atrialfibrillation, New York Heart Association functional class III or IV,perioperative acute myocardial infarction and use of an intra-aorticballoon. Its occurrence prolongs hospitalization and, above all, doubles therisk of mortality.