The effects of botulinum toxin A and papaverine on human saphenous vein and internal mammary artery grafts: an study.

Introduction: 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 or intraluminal injection before implantation may be used for spasm prophylaxis. This 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 was assessed.

Material And Methods: SV and IMA segments were suspended in organ baths, and isometric contraction responses to 2 different concentrations of 5-hydroxytryptamine (5-HT) and endothelin-1 (ET-1) were recorded after incubation with 2 different concentrations of BTX-A and papaverine at 2 time points (0 h and 2 h).

Results: The results revealed the following: 1) incubation with BTX-A and papaverine relaxes both SV and IMA rings contracted with 5-HT and ET-1; 2) the duration of the relaxant effect of BTX-A lasts longer than papaverine; and 3) no apparent histomorphological changes were observed in the grafts under light microscopy.

Conclusions: 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. The long-lasting vasodilatory effect of BTX-A on vascular smooth muscle may provide promising results in the prevention of venous and arterial graft spasm.