Myocardial Protection with Prophylactic Oral Metoprolol During Coronary Artery Bypass Grafting Surgery: Evaluation by Troponin I

INTRODUCTION:

Biochemical markers of myocardial injury are frequently altered after cardiac surgery. So far there is no evidence whether oral beta-blockers may reduce myocardial injury after coronary artery bypass grafting.

OBJECTIVE:

To determine if oral administration of prophylactic metoprolol reduces the release of cardiac troponin I in isolated coronary artery bypass grafting, not complicated by new Q waves.

METHODS:

A prospective randomized study, including 68 patients, divided in 2 groups: Group A (n=33, control) and B (n=35, beta-blockers). In group B, metoprolol tartrate was administered 200 mg/day. The myocardial injury was assessed by troponin I with 1 hour and 12 hours after coronary artery bypass grafting.

RESULTS:

No significant difference between groups regarding pre-surgical, surgical, complication in intensive care (15% versus 14%, P=0.92) and the total number of hospital events (21% versus 14%, P=0.45) was observed. The median value of troponin I with 12 hours in the study population was 3.3 ng/ml and was lower in group B than in group A (2.5 ng/ml versus 3.7 ng/ml, P<0,05). In the multivariate analysis, the variables that have shown to be independent predictors of troponin I release after 12 hours were: no beta-blockers administration and number of vessels treated.

CONCLUSION:

The results of this study in uncomplicated coronary artery bypass grafting, comparing the postoperative release of troponin I at 12 hours between the control group and who used oral prophylactic metoprolol for at least 72 hours, allow to conclude that there was less myocardial injury in the beta blocker group, giving some degree of myocardial protection.