Spontaneous slow flow in the saphenous vein graft: a relevant distinction of macrovascular endothelial dysfunction.

Spontaneous slow flow without significant obstructive stenosis, as encountered during diagnostic angiography, has mostly been reported in native coronary arteries. This phenomenon has been associated with angina, myocardial ischemia and infarction. Slow flow and "no-reflow" in saphenous vein grafts (SVG) have mostly been observed during percutaneous interventions as a complication from distal embolization. Spontaneous slow SVG flow, however, is rarely reported and correlation with clinical events not as well documented. A case of spontaneous slow flow in a SVG without significant obstructive lesions is presented, which correlated with the patient's anginal symptoms and ischemia on the stress myocardial perfusion scintigraphy. Percutaneous coronary intervention in the bypassed native coronary artery was successful resulting in the restoration of TIMI-3 coronary flow, resolution of the patient's symptoms, and normalization of the myocardial perfusion defects. The restoration of normal flow through the stented native coronary artery suggested endothelial dysfunction of the initial slow flow state was localized at the macrovascular level, specifically at the SVG conduit. Since bypass graft failure, as with native arterial atherosclerosis, has been attributed to impaired endothelial function at both the macrovascular and microvascular levels, localization of macrovascular endothelial dysfunction in the SVG as shown may be an instructive observation.