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.
Background Velocity-encoded, phase-difference magnetic resonance imaging (MRI) has been shown to provide an accurate assessment of shunt magnitude in patients with large atrial septal defects, but its ability to determine shunt magnitude in patients with intracardiac left-to-right shunts of various locations and sizes has not been evaluated in a prospective and blinded manner. The objective of the present study was to determine whether velocity-encoded, phase-difference MRI can assess the magnitude of intracardiac left-to-right shunting in humans. Methods and Results Twenty-one subjects (15 women and 6 men; age range, 15 to 72 years) underwent velocity-encoded, phase-difference MRI measurements of flow in the proximal aorta and pulmonary artery, followed immediately by cardiac catheterization. The presence of left-to-right intracardiac shunting was assessed with hydrogen inhalation, after which shunt magnitude was measured by the oximetric and indocyanine green techniques. Of the 21 patients, 12 had left-to-right intracardiac shunting detected by hydrogen inhalation. There was a good correlation ( r =.94) between the invasive and MRI assessments of shunt magnitude. In comparison to oximetry and indocyanine green, MRI correctly identified the 12 patients with a ratio of pulmonary to systemic flow (Qp/Qs) of <1.5 (9 without intracardiac shunting and 3 with small shunts) and the 9 patients with a Qp/Qs of ≥1.5 (6 with atrial septal defect, 1 with ventricular septal defect, 1 with patent ductus arteriosus, and 1 with both atrial septal defect and patent ductus arteriosus). Conclusions Compared with measurements obtained during cardiac catheterization, velocity-encoded, phase-difference MRI measurements of flow in the proximal great vessels can reliably assess the magnitude of intracardiac left-to-right shunting.
Background In the patient with mitral regurgitation who is being considered for valvular surgery, cardiac catheterization is usually performed to quantify the severity of regurgitation and to determine its influence on left ventricular volumes and systolic function. Magnetic resonance imaging (MRI) potentially provides a rapid, noninvasive method of acquiring these data. Thus, this study was done to determine whether MRI can reliably measure the magnitude of mitral regurgitation and evaluate the effect of regurgitation on left ventricular volumes and systolic function. Methods and Results Twenty-three subjects (14 women and 9 men 15 to 72 years of age) with (n=17) or without (n=6) mitral regurgitation underwent MRI scanning followed immediately by cardiac catheterization. The presence (or absence) of valvular regurgitation was determined, and left ventricular volumes and regurgitant fraction were quantified during each procedure. There was excellent correlation between invasive and MRI assessments of left ventricular end-diastolic ( r =.95) and end-systolic ( r =.95) volumes and regurgitant fraction ( r =.96). All MRI examinations were completed in <28 minutes. Conclusions In the patient with mitral regurgitation, MRI compares favorably with cardiac catheterization for assessment of the magnitude of regurgitation and its influence on left ventricular volumes and systolic function.
