Vasodilator responses of coronary conduit and resistance arteries to continuous nitroglycerin infusion in humans: A Doppler guide wire study

To examine the responses of coronary conduit and resistance arteries to the continuous i.v. administration of nitroglycerin in 15 patients with atypic al chest pain, we measured coronary blood flow velocity in the left anterio r descending coronary artery using a Doppler guide wire and the lumen diame ter and cross-sectional area by quantitative coronary angiography. Systolic flow, diastolic flow, total coronary flow, and coronary vascular resistanc e were calculated. Stepwise increases in dose of nitroglycerin resulted in significant dose-dependent decrease in mean aortic pressure (p < 0.01) and increase in lumen diameter (p < 0.05). After nitroglycerin administration o f 0.5 mug/kg/min, systolic flow decreased significantly by 89.9 +/- 15.7% ( p < 0.01), and diastolic flow increased significantly by 74.2 +/- 37.1% (p < 0.05). Total coronary flow did not change significantly with the various doses of nitroglycerin. However, coronary vascular resistance decreased sig nificantly at concentrations greater than 0.5 mug/kg/min nitroglycerin. Con tinuous nitroglycerin infusion did not reduce either diastolic or total cor onary blood flow despite a significant reduction in coronary perfusion pres sure. These results indicate that subendocardial blood flow might be mainta ined during continuous i.v. infusion of nitroglycerin within the clinical d ose range.