Variability of myocardial blood flow measurements by magnetic resonance imaging in the Multi-Ethnic Study of Atherosclerosis

OBJECTIVE: Magnetic resonance imaging (MRI) allows the noninvasive assessment of absolute myocardial blood flow (MBF) in mL/min/g during rest, and hyperemia induced by intravenous adenosine, a powerful coronary vasodilator with short decay time. The longitudinal variability in healthy volunteers of the hemodynamic response to adenosine, and of the MBF response, remain largely unknown. The purpose of this study was to assess the longitudinal variability for resting and hyperemic MBFs in the Multi-Ethnic Study of Atherosclerosis. MATERIALS AND METHODS: Thirty participants (19 women, 11 men, mean age 63.2 ± 9.6; range 45-79 years) underwent 2 MRI exams with an average separation of 334 ± 158 days (range: 20-645) between the 2 exams, using a rapid, multislice T1-weighted gradient-echo imaging technique at rest and during maximal vasodilation with intravenous adenosine. RESULTS: The absolute repeatability coefficient, corresponding to the 95% confidence intervals of the within subject differences, was 0.29 mL/min/g for rest studies, and 1.13 mL/min/g for hyperemic MBF. The relative repeatability coefficients, expressed as a percentage of the mean blood flow, averaged 30% at rest, and 41% during hyperemia. Differences in resting MBF between the 2 exams from 1.01 ± 0.22 to 0.91 ± 0.18 mL/min/g (P = 0.001) were associated with changes in hemodynamic conditions, but no such association was observed for hyperemic MBFs, which averaged 2.84 ± 0.87 mL/min/g in the first examination, and 2.69 ± 0.65 mL/min/g at follow-up. Over ∼1 year of aging between perfusion studies there was no observable decline of the hyperemic response, but the variability of the hyperemic MBF response increased with the lag between baseline and follow-up measurements. CONCLUSIONS: The repeatability of MBF measurements by MRI at rest was similar to results from previous studies with positron emission tomography.