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

Objectives. This study assessed changes in coronary flow velocity measured distal to 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 documented perfusion defect on dipyridamole-thallium-201 scintigraphy. Background. Significant flow inhomogeneity is believed to develop during coronary vasodilation induced by dipyridamole, causing defect in the thallium-201 scintigram. The recently developed intracoronary Doppler guide wire permits assessment of flow velocity variables in normal and stenotic arteries. Methods In 17 patients with stable angin 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 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). 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 perfusion defect on thallium-201 imaging. The degree of inhomogeneity is related to the extent of the perfusion defect.