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 meas ured distal to a significant stenosis of the left anterior descending coronary artery and at the adjacent normal left circumflex coronary ar tery, produced by intravenous administration of dipyridamole, in patie nts undergoing coronary angioplasty with a documented perfusion defect on dipyridamole-thallium-201 scintigraphy. Background. Significant fl ow inhomogeneity is believed to develop during coronary vasodilation i nduced by dipyridamole, causing a defect in the thallium 201 scintigra m. The recently developed intracoronary Doppler guide wire permits ass essment of how velocity variables in normal and stenotic arteries. Met hods. In 17 patients with stable angina me studied changes in time-ave raged peak velocity and the diastolic/systolic velocity ratio simultan eously using two 0.014-in, (0.36-mm) Doppler guide wires at baseline a nd after 4 min of dipyridamole infusion (0.56 mg/kg body weight). Coro nary bow velocity reserve and relative bow reserve were correlated wit h the degree of stenosis on coronary angiography and quantitative anal ysis of thallium-201 images. Results. No change in distal flow velocit y was observed in the stenotic vessel (5.5 +/- 33.7% [mean +/- SD]), i n contrast to a significant increase observed in the adjacent normal v essel (162.4 +/- 39.8%), Poststenotic coronary flow velocity reserve c orrelated with percent lumen diameter stenosis (r = -0.66, p < 0.05). A correlation was also observed between the relative flow reserve/thal lium-201 relative perfusion ratio (r = 0.90, p < 0.001). Conclusions. To our knowledge, these findings represent the first direct proof of d ipyridamole-induced flow inhomogeneity producing a perfusion defect on thallium-201, imaging. The degree of inhomogeneity is related to the extent of the perfusion defect.