High resolution CMR perfusion imaging demonstrates reduced flow reserve and endo/epi ratio in microvascular coronary disease

Background Patients with angina without obstructive coronary artery disease are increasingly recognized and microvascular disease (MVD) is felt to play a significant role. Patients with MVD have an abnormal myocardial perfusion reserve (MPR). An abnormal MPR by positron emission tomography is prognostic of increased cardiovascular events, particularly in women, diabetics, and those with metabolic syndrome. Also, high resolution CMR perfusion imaging has been shown to detect transmural differences in perfusion as evidenced by an endocardial-toepicardial ratio (EER) >1 in normal segments and a reduced ratio in segments with obstructive CAD. We hypothesize that there would be a global reduction in MPR and EER with stress due to subendocardial ischemia in patients with anginal symptoms and non-obstructive CAD/normal coronaries. Methods Patients with high suspicion for microvascular disease with angina or anginal equivalent symptoms with no significant epicardial stenosis as demonstrated by x-ray angiography underwent vasodilator stress perfusion studies on a 1.5T Siemens Avanto. High resolution firstpass spiral perfusion pulse sequences were performed. Sequence parameters included: 8 interleaves of variable density spirals from 0.75 to 0.2 Nyquist, 6.1ms readout per interleaf, TE 1.0 ms, TR 9ms, TI 80ms, FA 35, FOV 340mm, in-plane resolution 1.48mm. Images were acquired at 3 short axis slice locations during rest and stress (adenosine n=5, regadenoson n=8). Quantification of perfusion was performed on a pixel-wise basis using Fermi-function deconvolution after images were reconstructed by SPIRIT and then aligned with non-rigid registration ANTs (Advanced Normalization Tools).