The importance of the time of digitalization for the incidence of spasms evoked by ouabain in strips of human saphenous vein.

The extent of contracture induced by ouabain on preparations of the greater saphenous vein obtained from patients undergoing elective coronary bypass surgery was investigated. The medical pretreatment of the various donor patients was similar but differed with regard to the duration of preoperative digitalization ranging from several days to months. Whereas the maximal contraction induced by noradrenaline was not influenced by prior digitalization, the contracture evoked by ouabain showed a strong dependency on the duration of preoperative digitalization. In patients without or with only short-term preoperative digitalization the spasm exerted by ouabain amounted to 48.8% and 49.2%, respectively, of the maximal contraction induced by noradrenaline, and decreased to zero in patients with long-term digitalization. From this result it is concluded that, in patients after coronary artery bypass grafting who did not receive cardiac glycosides for long-term treatment, the acute administration of glycosides may be a mechanism responsible for the early occlusion of saphenous vein bypass grafts.