Effects of carvedilol on vascular reactivity in human left internal mammary artery

M. Guzeloglu, E. Ertuna, M.Z. Arun, B. Reel

Department of Cardiovascular Surgery, Optimed Hospital, Cerkezkoy-Tekirdag, Turkey. mehmetguzeloglu@optimedhastanesi.com

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• Pharmacology

OBJECTIVE: Surgical treatment choice for coronary artery disease is coronary artery bypass grafting (CABG) surgery. Left internal mammary artery (LIMA) is frequently used as an arterial graft in CABG operations. Perioperative spasm of LIMA can result in increased morbidity and mortality. Pharmacological interventions are routinely used for prevention and treatment of LIMA spasm. In this study, we aimed to investigate the effects of carvedilol, an alpha- and beta-adrenergic receptor blocker, on responses to endogenous vasoconstrictors which play a role in graft spasm and the possible interaction between carvedilol and diltiazem/papaverine which are vasodilators commonly used in CABG surgery.

PATIENTS AND METHODS: Isolated LIMA rings collected from patients undergoing CABG operation were suspended in an organ bath. Concentration-dependent responses to norepinephrine (NE), serotonin (5-HT) and diltiazem were examined before and after carvedilol incubation (10-6 M, 1 hour). Maximum relaxation response to papaverine (10-4 M) was compared in LIMA rings incubated with 0.05% dimethyl sulfoxide (DMSO, placebo) or carvedilol (10-6 M).

RESULTS: Carvedilol did not affect the maximal contractile response to NE; however, it significantly reduced the sensitivity of LIMA to NE. Carvedilol increased contractile response and sensitivity to 5-HT. Promisingly, carvedilol increased the vasodilatory effects of diltiazem and papaverine.

CONCLUSIONS: Our study suggests that carvedilol may be administered perioperatively in combination with diltiazem or papaverine to prevent or resolve LIMA graft spasm.

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