Magnetic resonance-based assessment of global coronary flow and flow reserve and its relation to left ventricular functional parameters - Comparison with positron emission tomography

Background-Measurement of coronary sinus blood now (CSF) by phase-contrast magnetic resonance (PC-MR) imaging at rest and during hyperemia may allow n oninvasive assessment of global coronary hemodynamics. Methods and Results-Sixteen healthy volunteers (age, 22 to 32 years) were e xamined with MR and PET in random order within 1 to 2 days. At rest and dur ing hyperemia (dipyridamole 0.56 mg/kg), CSF was measured by a cine PC-MR t echnique (temporal resolution, 40 ms; spatial resolution, 1.25x0.8 mm(2)), and myocardial blood flow (MBF) was measured by [N-13]NH3 PET.PET and MR ag reed closely for coronary flow reserve (CFR; mean difference, 2.2 +/- 14.7% ; Bland-Altman method). CSF divided by either total left ventricular mass o r an estimate of drained myocardium (LVMdrain) correlated highly with PET f low data (r=0.93 and 0.95, respectively) and with measures of oxygen demand , ie, heart rate, afterload-corrected fiber shortening, and peak systolic s tress determined by MR (overall correlation coefficients, 0.81 and 0.87, re spectively, multivariate analysis). CSF/LVMdrain did not differ significant ly from PET-derived MBF (difference, 3.6+/-16.6%). In orthotopic heart tran splant recipients (n=9), CFR was reduced and blood supply-demand relationsh ips 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 measur ements in patients. In transplanted hearts, elevated resting flow is the ma jor cause of reduced CFR.