Magnetic Resonance–Based Assessment of Global Coronary Flow and Flow Reserve and Its Relation to Left Ventricular Functional Parameters

Abstract

Background —Measurement of coronary sinus blood flow (CSF) by phase-contrast magnetic resonance (PC-MR) imaging at rest and during hyperemia may allow noninvasive assessment of global coronary hemodynamics. Methods and Results —Sixteen healthy volunteers (age, 22 to 32 years) were examined with MR and PET in random order within 1 to 2 days. At rest and during hyperemia (dipyridamole 0.56 mg/kg), CSF was measured by a cine PC-MR technique (temporal resolution, 40 ms; spatial resolution, 1.25×0.8 mm 2 ), and myocardial blood flow (MBF) was measured by [ 13 N]NH 3 PET. PET and MR agreed closely for coronary flow reserve (CFR; mean difference, 2.2±14.7%; Bland-Altman method). CSF divided by either total left ventricular mass or an estimate of drained myocardium (LVM drain ) correlated highly with PET flow data ( r =0.93 and 0.95, respectively) and with measures of oxygen demand, ie, heart rate, afterload-corrected fiber shortening, and peak systolic stress determined by MR (overall correlation coefficients, 0.81 and 0.87, respectively, multivariate analysis). CSF/LVM drain did not differ significantly from PET-derived MBF (difference, 3.6±16.6%). In orthotopic heart transplant recipients (n=9), CFR was reduced and blood supply-demand relationships at rest were shifted toward higher flows ( P <0.0001). Conclusions —This integrated MR approach allows comprehensive assessment of autoregulated and hyperemic coronary flow and is suitable for serial measurements in patients. In transplanted hearts, elevated resting flow is the major cause of reduced CFR.