Assessment of Coronary Arterial Flow and Flow Reserve in Humans With Magnetic Resonance Imaging

Abstract

Background The noninvasive measurement of absolute epicardial coronary arterial flow and flow reserve would be useful in the evaluation of patients with coronary circulatory disorders. Phase-contrast magnetic resonance imaging (PC-MRI) has been used to measure coronary arterial flow in animals, but its accuracy in humans is unknown. Methods and Results Twelve subjects (7 men, 5 women; age, 44 to 67 years) underwent PC-MRI measurements of flow in the left anterior descending coronary artery or one of its diagonal branches at rest and after administration of adenosine (140 μg·kg −1 ·min −1 IV). Immediately thereafter, intracoronary Doppler velocity (IDV) and flow measurements were made during cardiac catheterization at rest and after intravenous administration of adenosine. For the 12 patients, the correlation between MRI and invasive measurements of coronary arterial flow and coronary arterial flow reserve was excellent: coronary flow MRI (mL/min)= 0.85×coronary flow IDV (mL/min)+17 (mL/min), r =.89, and coronary flow reserve MRI =0.79×coronary velocity reserve IDV +0.34, r =.89. For the range of coronary arterial flows (18 to 161 mL/min) measured by MRI, the limit of agreement between MRI and catheterization measurements of flow was −13±30 mL/min; for the range of coronary reserves (0.7 to 3.7) measured by MRI, the limit of agreement between the two techniques was 0.1±0.4. Conclusions Cine velocity-encoded PC-MRI can noninvasively measure absolute coronary arterial flow in the left anterior descending artery in humans. PC-MRI can detect pharmacologically induced changes in coronary arterial flow and can reliably distinguish between those subjects with normal and abnormal coronary artery flow reserve.