Use of verapamil and nitroglycerin solution in preparation of radial artery for coronary grafting

Background. The radial artery (RA) has been used as an alternative arterial graft for coronary artery bypass grafting. This artery has been reported to be spastic; therefore, use of spasmolytic drugs (vasodilators) during the preparation of the RA is recommended. The combination of calcium antagonists and nitroglycerin (verapamil plus nitroglycerin, VG solution) has been suggested to be effective in other bypass grafts. This study was designed to investigate (1) the effect of the VG solution during preparation of the RA for coronary artery bypass grafting and (2) whether the effect would last for a prolonged period after topical use. Methods. Ring segments of the RA taken from coronary artery bypass grafting patients were studied in organ chambers at a physiologic pressure. The relaxation effect of VG (30 μmol/L verapamil and 30 μmol/L nitroglycerin, n = 5) or papaverine (30 μmol/L, n = 5) was recorded in K+ (25 mmol/L potassium chloride)-precontracted RA segments. Other segments taken from the RA were treated (n = 5) or not treated (n = 20, as the control) with the VG solution for 45 minutes before used for coronary artery bypass grafting. Both the VG-treated and nontreated segments were immersed in oxygenated Krebs solution and stored in a refrigerator at 4°C for 24 hours. The contraction force to 100 mmol/L K+ was compared between the two groups. Results. The VG solution induced more rapid relaxation than papaverine (p < 0.05 from the first to the ninth minute). After 10 minutes, both solutions induced full relaxation. The contraction to K+ (100 mmol/L) in rings treated with VG solution for 45 minutes during operation was almost abolished 24 hours later (0.86 ± 0.1 g). In contrast, the control segments (n = 20) taken from non-treated RA contracted with K+ to high force (5.0 ± 0.6 g; p < 0.001). Conclusions. The present study suggests that the combination of verapamil and nitroglycerin may provide a rapid onset, a complete relaxation, and a long-lasting vasorelaxant effect when used to prepare the RA for grafting. This study adds a new method to prevent RA spasm during coronary artery bypass grafting.