Preserved vasodilatory response to nitroglycerin in saphenous vein bypass grafts

Uncertainty exists regarding the effects of nitroglycerin on atherosclerotic segments of coronary arteries, and information on vasoreactivity of saphenous vein bypass grafts is sparse. Intravascular ultrasound enables identification of atherosclerosis in angiographically normal segments and allows continuous determination of alterations in cross-sectional lumen areas.

Patients with documented coronary atherosclerosis were studied. Vessel morphology and lumen area at baseline and after 100 to 200 micrograms nitroglycerin were assessed at 10-second intervals for 60 seconds in vessel segments without angiographically apparent lesions. Coronary artery saphenous vein bypass grafts from 11 patients were compared with native coronary arteries in 16 different patients. Atherosclerosis was present in all vessel segments studied. There was a rapid increase in lumen area compared with baseline after intravascular nitroglycerin in both native coronary arteries and saphenous vein bypass grafts. Maximum lumen area dilatation was 19.6 +/- 12.2% in saphenous vein bypass grafts and 19.7 +/- 13.1% in native coronary arteries. An earlier peak response in saphenous vein bypass grafts (34.5 +/- 6.9 seconds) compared with native coronary arteries (44.7 +/- 8.5 seconds; P = .003) was found. Vessel wall area remained constant during vasodilation, but there was a significant reduction in measured wall thickness (P = .034).

In patients with documented coronary artery disease, intravascular ultrasound reveals substantial atherosclerosis in angiographically normal vessel segments. In these vessel segments, both native coronary arteries and saphenous vein bypass grafts exhibit prompt vasodilation with the intravascular administration of nitroglycerin. The vasodilatory capacity in response to nitroglycerin seems to be preserved in transposed, denervated, and devascularized saphenous veins.