Effects of Nitroprusside and Nitroglycerin on Coronary Blood Flow in Stenotic Arteries: Study in Patients with Single-Vessel Coronary Artery Disease

Objectives. To assess the effect of intravenous sodium nitroprusside and nitroglycerin on coronary blood flow distal to a severe coronary artery stenosis. Methods. Parameters of coronary arteries and coronary blood flow were measured distally to the stenosis during nitroprusside and nitroglycerin infusions in a dose producing a 25% decrease in mean arterial blood pressure in patients with single-vessel coronary artery disease. Results. Twenty patients (19 male, mean age 54.25 +/- 9.72 years), with a 52-90% diameter reduction of the left anterior descending (LAD) artery were included in this study. Compared to baseline, only nitroglycerin produced a significant increase in the minimal lumen diameter of 18.02 +/- 4.26% and minimal lumen area of 42.69 +/- 10.18%. Both medications increased the distal vessel diameter. Nitroglycerin also produced a significant increase in the reference segment diameter. Despite the substantial pressure drop, there was no decrease in coronary blood flow (at rest or during hyperemia produced by intracoronary adenosine) or coronary flow reserve with both drugs. Nitroglycerin increased the hyperemic diastolic/systolic velocity ratio by 21.57 +/- 8.97% (p < 0.05). Compared to baseline, there were significant reductions in the total and minimal coronary vessel resistance indices for both nitroprusside and nitroglycerin. Conclusion. In patients with a severe single coronary atherosclerotic lesion, intravenous infusion of nitroprusside and nitroglycerin in a dose sufficient to produce a substantial drop in mean arterial pressure does not lead to any decrease in coronary blood flow or coronary flow reserve.