What cardiologists need to know about cardiovascular magnetic resonance (CMR)

Abstract

What cardiologists need to know about cardiovascular magnetic resonance (CMR) acquire and interpret the scan. CMR is an interactive process that doesn't just require the operator to simply "push a button".Clinical scans are acquired on a 1.5 or 3 Tesla machine. Surprisingly the stronger field strength does not always provide superior cardiac imaging due to a number of specific artifacts at 3T.(2) Most scans generally take 20 -40 minutes to complete although more complex cases such as adult congenital imaging can take up to 1 hour. The patient therefore has to be able to tolerate lying supine, generally, for this period of time without a break -which can be problematic in patients with decompensated heart failure.Images are acquired during breath-holds of 10 -15 seconds. The image is formed from data collected over consecutive heartbeats and mis-registration occurs if the heart is moving with respiration.Similar artifacts occur with arrhythmias which can render a scan non-diagnostic. Controlled atrial fibrillation and low frequency ectopy are manageable, high frequency ectopy can however cause major problems. Pharmacological control of the arrhythmia should be considered prior to imaging (e.g. beta blockers).