CORONARY FLOW AND CORONARY FLOW RESERVE MEASUREMENTS IN HUMANS WITH BREATH-HELD MAGNETIC-RESONANCE PHASE-CONTRAST VELOCITY MAPPING

Objective evidence for coronary lesion significance can be obtained wi th ischemic stress testing, Since flow-limiting stenoses have already undergone compensatory vasodilatation to maintain flow, the response t o vasoactive stimulation is dampened. The degree of response limitatio n is reflected by the coronary flow reserve (CFR), Absolute volume flo w rates can be accurately and noninvasively measured with MRI techniqu es, The purpose was to assess the ability to measure coronary volume f low rate noninvasively, and characterize the effect of pharmacologic s tress on coronary flow quantitatively by using ultrafast, breath-held segmented k-space phase-contrast-MR imaging (PC-MRI), Ten healthy volu nteers were examined by using ultrafast breath-held PC-MRI. Coronary v olume flow rates were measured in the anterior descending coronary art ery (LAD) at rest and following intravenous administration of dipyrida mole. CFR was determined based on these data. Mean LAD volume flow rat es increased from 38 +/- 11 ml/min before application of dipyridamole to 169 +/- 42 ml/min, The mean CFR amounted to 5.0 +/- 2.6 (median = 4 .15). This study demonstrates the feasibility of breath-held PC-MRI to noninvasively quantify coronary volume flow rates over the cardiac cy cle, Pharmacologically induced changes in volume flow rate and thus CF R can be quantitated.