Magnetic Resonance First-Pass Myocardial Perfusion Imaging

Magnetic resonance first-pass perfusion imaging has developed considerably over the past decade. It is possible to acquire 7-8 imaging planes every heartbeat at rest and in two heartbeats during stress using high-performance gradients and hybrid echoplanar methods. T1 weighting can be achieved with volumetric saturation pulses or selective "notch" pulses. First-pass studies can be quantified, but it also is possible to directly visualize myocardial perfusion abnormalities as subendocardial defects with less contrast enhancement than surrounding myocardium. It is feasible to detect stress-induced perfusion abnormalities in patients with coronary artery disease. Magnetic resonance imaging (MRI) perfusion abnormalities associated with myocardial infarction have significantly different characteristics from those seen on nuclear methods such as thallium, where the final appearance of images represents a combination of perfusion, viability, and wall thickness. Infarcted myocardium enhances during the first-pass MRI study unless there is microvascular or epicardial obstruction. Microvascular obstruction after myocardial infarction is easily detected and has adverse prognostic significance. Stress-induced perfusion abnormalities are not synonymous with coronary artery disease, as they can be detected in hypertrophic cardiomyopathy. MRI perfusion methods appear promising as long as physicians interpret the results in accordance of the physiology portrayed in the images.