Pathophysiology and Natural History Coronary Flow Reserve

To determine the effects of coronary angioplasty on coronary flow reserve (CFR), we studied 32 patients before and immediately after single-vessel coronary angioplasty and 31 patients evaluated late after angioplasty (7.5 + 1.2 months, mean + SEM). The geometry (percent area stenosis and minimal cross-sectional area) of each lesion was determined by quantitative coronary angiography (Brown/Dodge method) and the integrated optical density was measured by videodensitometry. CFR was measured with a No. 3F coronary Doppler catheter placed immediately proximal to the lesion and a maximally vasodilating dose of intracoronary papaverine. The translesional pressure gradient was obtained in all lesions before and immediately after angioplasty and in 18 of 31 vessels late after angioplasty. CFR immediately after angioplasty returned to normal levels (> 3.5 peak/resting velocity ratio) in 14 of 31 patients and was improved, although not normalized, in the remaining 17 patients. CFR immediately after dilation was not significantly correlated with any of the angiographic variables of arterial stenosis nor the resting pressure gradient. Moreover, the pressure gradient and absolute distal coronary pressure at peak hyperemia were not significantly different in vessels with normal and those with abnormal flow reserve immediately after dilation, suggesting that the residual stenosis did not significantly limit hyperemia. Late after angioplasty, however, a significant relationship emerged between CFR and all four indexes of residual arterial stenosis (percent area stenosis r = .70, p < .01; minimum arterial cross-sectional area r = .70, p < .01; integrated optical density r = .60, p < .01; and translesional pressure gradient r = .77, p < .01). Furthermore, in the absence of restenosis, CFR eventually normalized in all patients. These findings demonstrate that in one-half of patients there is a transient reduction in coronary flow reserve immediately after angioplasty. In the absence of restenosis, coronary flow reserve later normalizes. Consequently, measurements of coronary flow reserve immediately after angioplasty may not reflect the eventual success of the procedure in removing physiologic obstruction to coronary blood flow. Circulation 77, No. 4, 873-885, 1988. ALTHOUGH coronary angioplasty has been shown to increase coronary luminal cross-sectional area,1 reduce the translesional pressure gradient,2 ameliorate the symptoms of myocardial ischemia,3' 4and normalize previously positive noninvasive studies of provokable myocardial ischemia (e.g., exercise electrocardiographic,3' thallium-201 scintigraphic,4 and diastolic From the Department of Internal Medicine and the Cardiovascular Center, University of Iowa, and the Veterans Administration Hospital, Iowa City, and the Department of Medicine, University of Minnesota, Minneapolis. Supported by grants from the National Heart, Lung, and Blood Institute (HL27633, 14388, 00916, and 29976), the Ischemic SCOR (HL32295-01), and the Veterans Administration (MRIS 1100.2). This work was done during the tenure of a Clinician-Scientist from the American Heart Association and the funds were contributed in part by the Iowa and Minnesota Affiliates. Address for correspondence: Robert F. Wilson, M.D., Division of Cardiology, Department of Medicine, University of Minnesota Hospital and Clinic, Minneapolis, MN 55455. Received Jan. 21, 1987; revision accepted Jan. 14, 1988. Vol. 77, No. 4, April 1988 ventricular function studies6), its efficacy in restoring normal coronary flow reserve has been difficult to assess. It has been proposed that measurements of coronary flow reserve be used during angioplasty to determine when physiologically significant obstruction to coronary blood flow has been removed.7' 8 One group of investigators, however, has reported that flow reserve in dilated coronary arteries, although improved, was still depressed compared with that in normal vessels.8' 9 They attributed this failure of coronary reserve to normalize to the effects of diffuse residual atherosclerosis. Other investigators, however, have found flow reserve to normalize immediately after dilation.l° 11 The explanation for these prior inconsistent results might reside in methodologic difficulties in measuring maximal coronary flow reserve, problems in quanti873 by gest on A ril 4, 2017 http://ciajournals.org/ D ow nladed from