Sudden occlusion of a saphenous vein bypass graft relieved by direct injection of nitroglycerin.

An unusual case of sudden occlusion of a saphenous vein bypass graft to the right coronary artery, during a coronary angiographic study, is presented. Such occlusion was relieved by direct intragraft nitroglycerin injection, as typically happens in case of coronary arterial spasm. A possible pathogenetic mechanism, based on the present knowledge of platelet aggregation and the role of the powerful vasoactive agent Thromboxane A2, is discussed.