Noninvasive test of nitrate-induced coronary vasomotion by 1.5-T whole-heart 3D magnetic resonance angiography using a T2-prepared SSFP sequence.

This study was aimed to investigate the use of 1.5-T whole-heart 3D coronary MRA employing a T2-prepared SSFP sequence for assessing epicardial coronary artery vasodilation following exogenous nitrates. Navigator-gated whole-heart 3D coronary MRA was performed before and after sublingual nitroglycerin (NTG) in 22 volunteers and a T2-prepared SSFP sequence was used for imaging of coronary arteries without MR contrast agent. Coronary cross-sectional area was measured on pre- and post-NTG images of equivalent coronary segments in the major coronary arteries and whole-heart coronary vasodilation was analyzed quantitatively. Measurements were obtained by two independent investigators. Coronary vasodilation could be observed directly on multiplanar reformatted and three-dimensional volume-rendered MR images. On quantitative analysis, NTG administration results in the whole-heart coronary vasodilation by an average of 37.3 ± 12.7%. There was moderate yet significant correlation between the NTG-induced vasodilation and age (r = -0.52, P = 0.02). The mean absolute cross-sectional area of the coronary arteries was significantly higher after sublingual NTG in all the major coronary arteries. The coronary area measurements had an interobserver variability of 8 ± 3% and an intraobserver variability of 4 ± 2%. Non-contrast-enhanced 1.5-T SSFP whole-heart coronary MRA can noninvasively measure endothelium-independent coronary vasodilation over the entire heart with high feasibility and is a promising noninvasive method to explore whole-heart coronary smooth muscle cell function following exogenous nitrates in clinical practice.