Comparing the effects of frequently used Βeta blockers (nebivolol,metporolol) on the vascular nitric oxide levels of the coronary by-pass surgery patients

IVABSTRACTCOMPARING THE EFFECTS OF FREQUENTLY USED ΒETA BLOCKERS(NEBIVOLOL,METPOROLOL) ON THE VASCULAR NITRIC OXIDE LEVELS OFTHE CORONARY BY-PASS SURGERY PATIENTSDr. Ekrem BAYAR, Residency Thesis, Department of Cardiovascular SurgerySupervisor: Associate Prof. Dr. Hasim USTUNSOYMay 2007, 61 pagesGraft stenosis and graft spasm seen in arterial grafts are stil an importantproblem in coronary artery by-pass surgery. Metoprolol and nebivolol are β1adrenergic blockers. Nebivolol plays an important role in the modulation of nitricoxide(NO) secretion in arterial and venous endothelium. NO primarily inhibites theaggregation and adhesion of platelets and other blood cells and contributes to thedilatation of vessels.Fifty five patients undergoing CABG operation had been included to our study.Patients were seperated to 3 groups. The effects of preoperative metoprolol andnebivolol administration on nitric oxide levels in vascular graft endothelium andvascular graft vasovasorum was campared with controls.LIMA preparation was made in patients with suituble sternums. In patients withmore than one coronary artery stenosis, saphenous ven were added. Tissue sampleswere collected from these grafts and evaluated by immunohystochemistrical methods.There were not statisticly significant differences in the age, sex, diabetesmellitus, hypertension and hyperlipidemia parameters of the groups.The highest activity in both endothelium and vasovasorum levels in LIMA andsaphenous graft was measured in the nebivolol group. Metoprolol did not increaseNO activity in tissue level when compared with the controls.These findings suggest that nebivolol administration before and after coronaryby-pass surgery(uless contraindicated) may be useful in the maintenance of graftpatency by its NO mediated vasodilating effects.Key Words: Coronary artery by-pass grefting, nitric oxide, beta receptor antagonists,nebivolol