PREVENTING GASTROEPIPLOIC ARTERY SPASM - PAPAVERINE VS CALCIUM-CHANNEL BLOCKADE

The gastroepiploic artery (GEA) is a highly vasoactive artery gaining wider acceptance as a conduit for coronary artery bypass surgery. A va riety of agents are used to dilate the GEA prior to grafting; however, little is known about the duration of their effect in the immediate p ostoperative period. This study evaluated three calcium channel blocke rs and papaverine in preventing graft spasm. Methods: Porcine GEA segm ents (10-12 cm in length) were connected to a computer-controlled perf usion system with a constant in-flow pressure and distal resistance to simulate bypass flow (80-100 ml/min). Norepinephrine (NE; 10(-9) to 1 0(-5) M) was given in incremental doses at baseline before the vasodil ator, immediately after (0 hr), and again at 2 hr after the vasodilato r. Changes in flow and ED50 were recorded. Group INT (N = 25) received papaverine (PAP), diltiazem, nifedipine (NFP), or verapamil (VPL) int raluminally, while group EXT (N = 25) received the same dilators exter nally. Results: All arteries showed dose-dependent vasoconstriction to NE prior to treatment. Immediately after receiving the vasodilator, a rteries in both groups (INT and EXT) showed initial protection against NE-induced spasm with the exception of arteries receiving NFD externa lly. However, at 2 hr, for group INT, only VPL and NFD prevented NE-in duced graft spasm (VPL: 40.4 +/- 6.8 ml/min vs 17.9 +/- 3.3 ml/min and NFD: 27.0 +/- 6.5 ml/min vs 13.1 +/- 0.9 ml/ min, P < 0.02). In group EXT, after 2 hr, only VPL- and PAP-treated grafts showed resistance t o NE-induced vasospasm (VPL: 35.6 +/- 7.3 ml/min vs 15.0 +/- 6.9 ml/mi n and PAP: 47.4 +/- 15.1 ml/min vs 8.0 +/- 2.0 ml/min, P < 0.001). Con clusions: Papaverine, a lipophilic vasodilator, when given externally on the perivascular fat of the GEA, prevented graft spasm for up to 2 hr. In contrast, intraluminally applied papaverine did not show graft protection against NE-induced spasm. Nifedipine prevented NE-induced s pasm only when given intraluminally. Verapamil proved to be the most p otent and versatile vasodilator with effective graft protection of up to 2 hr whether applied externally or internally and was the preferred agent for protecting against GEA spasm. (C) 1997 Academic Press.