Abstract 1077: Non-Invasive MRI Assessment of Coronary Endothelial-Dependent Vasoreactivity
Endothelial-dependent coronary artery vasoreactivity is an important indicator of vascular function and is traditionally measured invasively. We hypothesized that coronary vasoreactivity can be measured non-invasively and abnormal function detected using high-field MRI. We studied 16 healthy adults (mean age ± SD 41.1±14.1 years, seven men) and eight patients with coronary artery disease (CAD, mean age 56.6±11.3, two men). To measure endothelial-dependent vasoreactivity, 3T coronary MRI was performed before and during continuous isometric hand-grip exercise, a known endothelial-dependent stressor. Cross-sectional coronary artery area and peak diastolic coronary flow velocities were quantified. In healthy adults, coronary arteries significantly dilated and increased in flow velocity with stress (baseline vs. stress area: 13.0±3.0 vs.14.9±4.1mm2, p<0.001; and velocity: 23.4±7.7 vs. 31.2±11.2 cm/s, p<0.0001). In CAD patients, the coronary arteries did not dilate (baseline vs. stress area: 18.4±5.2 vs. 17.5±4.5mm2, p=0.11) and decreased in flow velocity with stress (24.2±9.2 vs. 20.6±5.9cm/s, p=0.04). Relative changes are shown in Figure 1⇓. We provide first evidence that MRI and isometric handgrip exercise, an established endothelial-dependent stressor, non-invasively detects significant changes in two common indices of coronary endothelial vasoreactivity: coronary artery area and flow velocity. This novel technique demonstrates physiologic coronary artery vasodilation and increased flow velocity in healthy subjects in response to handgrip stress, and their pathologic absence in patients with CAD.