Effects of botulinum toxin A and papaverine on human saphenous vein and internal mammary artery grafts: an in vitro study

Abstract

Autologous saphenous vein (SV) and internal mammary artery (IMA) are used as bypass conduits during coronary artery bypass graft surgery. Vasospasm of the arterial and venous grafts may constitute a significant clinical problem. Pretreatment with a vasodilator drug of the graft ex vivo or intraluminal injection before implantation may be used for spasm prophylaxis. This in-vitro study was designed to assess the vasoactive effects and time-dependent changes of botulinum toxin A (BTX-A) and papaverine pretreatment on vasospasm of human SV and IMA grafts. Also histomorphology of the vessels were assessed.SV and IMA segments were suspended in organ baths and isometric contraction responses to two different concentrationsof 5-hydroxytryptamine (5-HT) and endothelin-1 (ET-1) were recorded after incubation with two different concentrations of BTX-A and papaverine at two time points (0 hours and 2nd hour).The results suggest that; 1) incubation with BTX-A and papaverine relaxes both SV and IMA rings contracted with 5-HT and ET-1, 2) duration of the relaxant effect of BTX-A lasts longer than papaverine, 3) no apparent histomorphologic changes are observed in the grafts under light microscopy.This study demonstrates that in human SV and IMA grafts, pretreatment with both BTX-A and papaverine are safe and have a potent inhibitory effect depending on the vessel and vasoconstrictor agent. Long lasting vasodilatory effect of BTX-A on vascular smooth muscle may provide promising results for preventing venous and arterial graft spasm.