QUANTITATION OF CARDIAC-OUTPUT WITH VELOCITY-ENCODED, PHASE-DIFFERENCE MAGNETIC-RESONANCE-IMAGING

Velocity-encoded, phase-difference magnetic resonance imaging (MRI) pr eviously has been used to measure flow in the aorta, as well as in the pulmonary, carotid, and renal arteries, but these measurements have n ot been validated against currently accepted invasive techniques. To d etermine he accuracy of velocity-encoded, phase-difference MRI measure ments of cardiac output, 23 subjects (11 men and 12 women, aged 15 to 72 years) underwent velocity-encoded, phase-difference MRI measurement s of cardiac output in the proximal aorta, followed immediately by car diac catheterization, with measurement of cardiac output by the Fick p rinciple and by thermodilution. For MRI, Fick, and thermodilution meas urements, stroke volume was calculated by dividing cardiac output by h eart rate. The magnetic resonance images were acquired in 1 to 3 minut es. For all patients, the agreement between measurements of stroke vol ume was 3 +/- 9 ml for MRI and Fick, -3 +/- 11 ml for MRI and thermodi lution, and 0 +/- 8 ml for MRI and he average of Fick and thermodiluti on. Compared with standard invasive measurements, velocity-encoded, ph ase-difference MRI can accurately and rapidly determine cardiac output .