Measurement of maximal coronary flow reserve: a technique for assessing the physiologic significance of coronary arterial lesions in humans.

Recent studies suggest that angiographic measurements of coronary arterial stenosis are poorly correlated with direct measurements of the capacity of the artery to conduct hyperemic blood flow. Direct measurement of coronary blood flow and the flow reserve capacity of individual coronary vessels in conscious humans, however, has been hampered by methodologic limitations. We have developed and validated a coronary Doppler catheter capable of subselectively measuring coronary blood flow velocity at the time of cardiac catheterization. Studies in seven calves demonstrated that measurements of the change in coronary blood flow velocity assessed using the Doppler catheter were highly correlated with simultaneous measurements of the change in coronary sinus blood flow (r = 0.97, slope = 1.06) and changes in blood flow velocity assessed using an epicardial Doppler probe (r = 0.95, slope = 1.04). Additional studies demonstrated that the catheter did not produce physiologically significant obstruction to coronary blood flow. Subsequent studies in 215 humans undergoing catheterization have shown that acceptable signals of phasic coronary blood flow velocity could be recorded in 176 patients. Subsequent dose response kinetic studies demonstrated that intracoronary administration of papaverine can rapidly produce maximal coronary hyperemia, equivalent in magnitude to intravenous dipyridamole, but short enough in duration to permit multiple measurements of coronary flow reserve during a single catheterization. Measurements of coronary flow reserve in patients with obstructive coronary artery disease have permitted characterization of the physiologic significance of individual obstructive coronary lesions. The development of this coronary Doppler catheter system and technique for measurement of maximal coronary flow reserve should facilitate characterization of the physiologic impact of coronary arterial lesions on coronary blood flow and studies of the coronary circulation in conscious humans.