Coronary flow velocity changes after intravenous dipyridamole infusion: Measurements using intravascular Doppler guide wire a documentation of flow inhomogeneity

Objectives.This study assessed changes in coronary flow velocity measured distal to a significant stenosis of the left anterior descending coronary artery and at the adjacent normal left circumflex coronary artery, produced by intravenous administration of dipyridamole, in patients undergoing coronary angioplasty with a documented perfusion defect on dipyridamole-thallium-201 scintigraphy.Background.Significant flow inhomogeneity is believed to develop during coronary vasodilation induced by dipyridamole, causing a defect in the thallium-201 scintigram. The recently developed intracoronary Doppler guide wire permits assessment of flow velocity variables in normal and stenotic arteries.MethodsIn 17 patients with stable angina we studied changes in time-averaged peak velocity and the diastolic/systolic velocity ratio simultaneously using two 0.014-in. (0.36-mm) Doppler guide wires at baseline and after 4 min of dipyridamole infusion (0.56 mg/kg body weight). Coronary flow velocity reserve and relative flow reserve were correlated with the degree of stenosis on coronary angiography and quantitative analysis of thallium-201 images.Results.No change in distal flow velocity was observed in the stenotic vessel (5.5 ± 33.7% [mean ± SD]), in contrast to a significant increase observed in the adjacent normal vessel (162.4 ± 39.8%). Poststenotic coronary flow velocity reserve correlated with percent lumen diameter stenosis (r = −0.66, p < 0.05). A correlation was also observed between the relative flow reserve/thallium-201 relative perfusion ratio (r = 0.90, p < 0.001).Conclusions.To our knowledge, these findings represent the first direct proof of dipyridamole-induced flow inhomogeneity producing a perfusion defect on thallium-201 imaging. The degree of inhomogeneity is related to the extent of the perfusion defect