The comparative effects of esmolol and amiodarone on isolated coronary artery bypass grafts

Background/aim: Esmolol and amiodarone are two most commonly used antiarrhythmic drugs in coronary artery bypass grafting (CABG) surgery. Nevertheless, blockade of beta-2 receptors by increasing doses raise concerns about possible vasospasms. We studied the vasoactive effects of amiodarone and esmolol on left internal mammary artery (LIMA), radial artery (RA), and saphenous vein (SV) grafts. Materials and methods: After determining the presence of functional smooth muscle and endothelial layers, the responses of submaximally preconstricted graft samples were recorded in a tissue bath system. A total of 96 graft samples from 40 patients were used: 16 LIMA, 16 RA, and 16 SV grafts for each drug. Esmolol and amiodarone were added to reservoirs separately, starting from a concentration of 10-8 M until a concentration of 10-4 M. Results: Although both drugs caused vasodilatation, amiodarone exhibited a more potent vasodilatory effect than esmolol (P < 0.0001 for LIMA, P = 0.0128 for RA, and P < 0.0001 for SV). The vasodilatation rates with esmolol were 48.99 ± 2.28% in LIMA, 49.77 ± 3.03% in RA, and 41.90 ± 4.05% in SV grafts and with amiodarone they were 71.65 ± 5.18% in LIMA, 58.61 ± 5.87% in RA, and 65.07 ± 4.09% in SV grafts. Conclusion: This in vitro study revealed that even increasing doses of both drugs induce vasodilatation of CABG grafts, with amiodarone having a more potent vasodilatory effect than esmolol.