Evaluation of the effects of systemic nitroglycerin on perfusion of ischemic myocardium in coronary heart disease assessed intraoperatively by antegrade blood flow through intact saphenous vein bypass grafts

To evaluate systemic nitroglycerin (NTG) effects on reduced perfusion of ischemic myocardium in coronary disease, intravenous NTG actions on coronary circulatory dynamics were directly assessed intraoperatively during aortocoronary bypass surgery in 24 patients. Thus metered antegrade blood flow was measured through 56 separate intack saphenous vein bypass grafts to analyze NTG perfusion response in the obstructed native coronary artery (CA). In 34 bypassed CA with proximal luminal diameter narrowing > 50% to 90%, NTG reduced (p < 0.01) graft flow (GF) 82 to 63 cc/min, thereby Indicating that NTG dilated proximal stenoses with resultant increased CA flow. In 11 bypassed CA obstructed > 90% to 100% with well developed collaterals distally, NTG decreased (p < 0.05) GF 64 to 53 cc/min, thus indicating enhanced collateral flow. In contrast, in 11 bypassed CA obstructions > 90% to 100% without collaterals, that NTG increased (p < 0.02) GF 91 to 100 cc/min indicated NTG nonresponsiveness of the severely diseased CA. Thus systemic NTG improves perfusion to ischemic myocardlum subserved by diseased coronaries with < 90% stenosis or by > 90% obstructed vessels with substantial collaterals distally.