Prevention of radial artery graft vasospasm after coronary bypass

Background. Pharmacologic prophylaxis for prevention of notorious radial artery (RA) spasm is critical because of the increasingly routine use of the RA conduit during coronary bypass. Therefore, we investigated the vasodilatory effect of calcium antagonist in combination with nitroglycerin (NTG) RA segments. Methods. We evaluated the vasodilatory effect of nifedipine alone, verapamil alone, diltiazem alone, NTG alone, and calcium antagonist in combination with in endothelin-1 (ET-1)-, angiotensin II (AII)-, 5-hydroxytryptamine (5-HT)-, and norepinephrine (NE)-precontracted human RA rings mounted in organ baths. Results. Nifedipine (10−5 M) alone, diltiazem (10−5 M) alone, verapamil (10−5 M) alone, and NTG (10−5 M) alone showed maximum vasodilatory effect in either 10−7 M ET-1-, 10−7 M AII-, 10−5 M NE-, or 10−4 M 5-HT-precontracted RA segments. The 10−5 M NTG alone-induced vasodilation (88.5% ± 7.7%) in ET-1-precontracted segments was the highest vasodilation (ANOVA, p = 0.0008) among NTG alone-induced vasodilatory effects in RA. The relaxing effect of any of the calcium antagonists alone varied from 32.7% ± 13.2% to 76.5% ± 20.5% in RA precontracted with different vasoconstrictors. Nearly 200% vasodilation was observed with calcium antagonist in combination with NTG in AII-precontracted vessels. Nonetheless, the vasodilatory effect of calcium antagonist in combination with NTG in RA segments precontracted with different vasoconstrictors other than AII was nearly 100%. Conclusions. A calcium antagonist in combination with NTG is more potent than calcium antagonist alone or NTG alone in prevention of human RA vasospasm after coronary bypass.