THE COMPARISON OF THE RESPONSIVENESS OF HUMAN ISOLATED INTERNAL MAMMARY AND GASTROEPIPLOIC ARTERIES TO LEVCROMAKALIM - AN ALTERNATIVE APPROACH TO THE MANAGEMENT OF GRAFT SPASM

Aims We studied the effectiveness of levcromakalim, a potassium channe l opener (KCO), in the prevention and reversal of spasm in arterial gr afts used in coronary artery bypass operations, namely, internal mamma ry artery (IMA) and gastroepiploic artery (GEA). Methods Spasm was mim icked in vitro in arterial rings from 109 patients by increasing the v ascular tension with noradrenaline, the thromboxane analogue U46619, e ndothelin-1 and K+. Results GEA displayed considerably higher contract ile force to these agents than IMA. Pretreatment with levcromakalim de pressed significantly the maximal contractile responses (either absolu te or relative) to noradrenaline and U46619 but did not affect those o f endothelin-l and K+ in both of the arteries. Sensitivities (to all a gents, except to endothelin-l) decreased significantly after levcromak alim. In experiments evaluating the antispasmodic activity of levcroma kalim, a higher relaxant capacity was observed in GEA than IMA (for K contraction; IMA: 31.32 +/- 3.83%, n = 13 vs GEA: 98.01 +/- 0.71%, n = 7, P < 0.05). This different activity of levcromakalim between two a rterial grafts was apparent even when GEA rings were contracted to hig her force (g) than that ofIMA (for K+ contraction; GEA: 72.56 +/- 4.96 %, n = 7). Responses to levcromakalim were similar in IMA and GEA when endothelin-l was used as the spasmogenic agent (IMA: 80.98 +/- 4.85%, n = 10 vs GEA: 91.93 +/- 3.17%, n = 7, P > 0.05). Conclusions Our res ults provide evidence that levcromakalim may have a therapeutic value in the treatment of spasm of coronary artery bypass grafts, especially GEA.