The effect of nebivolol on internal mammary artery blood flow during coronary artery bypass graft surgery

Abstract

During coronary artery bypass grafting (CABG), one of the most important complications related to the internal mammary artery (IMA) is perioperative spasm. Nebivolol causes endothelium-dependent vascular relaxation by increasing nitric oxide (NO) release and prevents endothelial dysfunction in long-term use. In our study, we measured the effect of a third generation beta blocker, nebivolol, on the flow dynamics of IMA grafts. We recruited 90 hypertensive patients undergoing isolated CABG operation, who were divided into three groups and each group included 30 patients: Group 1 patients were under antihypertensive treatment other than beta-blockers (angiontensin-converting enzyme [ACE] inhibitors, calcium channel blockers or diuretics; monotherapy or combination therapy), Group 2 received metoprolol (50 mg/day) and Group 3 received nebivolol (5 mg/day). These antihypertensive therapies were given for at least one week before the operation and continued thereafter. IMA blood flow volume was measured for one minute just before cardiopulmonary bypass (measurement A) and before left internal mammary artery (LIMA)-left anterior descending (LAD) artery anastomosis (measurement B) in the three groups. Cardiac output measurements were also achieved simultaneously. The measurement A results were 56.3 ± 36.2, 54.6 ± 28.1 and 66.8 ± 34.2 mL/min in Groups 1, 2 and 3, respectively (p<0.05). The measurement B results were 78.3 ± 29.6, 80 ± 28.8 and 91.1 ± 40.8 mL/min in Groups 1, 2 and 3 (p<0.05), respectively. There were no differences in cardiac outputs among the groups; 5.2 ± 1.4, 5.0 ± 1.6 and 5.3 ± 1.1 L/min (p>0.05). While the cardiac outputs were similar within the three groups, the IMA free flow volume was higher in the nebivolol group after local papaverine use. Nebivolol might represent a good choice in hypertensive patients undergoing cardiac surgery by preventing perioperative myocardial hypoperfusion which increases early morbidity and mortality.