Cardiovascular Magnetic Resonance Imaging in Mitral Regurgitation

Background Cardiovascular magnetic resonance (CMR) is the reference-standard for biventricular assessment and has potential diagnostic and prognostic advantages in the assessment of primary mitral regurgitation (MR). Aims 1) To establish whether 4-dimensional flow CMR (4DF-CMR) has associations with post-operative LV reverse remodelling in primary MR. 2) To evaluate feasibility and reproducibility of exercise-CMR in asymptomatic, primary MR. 3) To attempt to develop a clinically applicable pulse sequence for acquisition of 4DF-CMR during continuous exercise. 4) To assess the incidence and characteristics of silent cerebral infarction (SCI) in mitral valve surgery for primary MR. Methods 1) Forty-four patients with primary MR underwent 4DF-CMR at index assessment. Of those, 29 patients underwent mitral valve surgery and subsequently a follow-up CMR scan at 6-months. 2) Twenty-five asymptomatic patients with primary MR underwent CMR during continuous in-scanner exercise, utilising a free-breathing, respiratory navigated Compressed-SENSE pulse sequence for the acquisition of short-axis cine stack and aortic flow. 3) Ten healthy volunteers underwent 4DF-CMR acquisition during continuous in-scanner exercise. The clinically available 4DF-CMR pulse sequence was optimised during 6 attempts to allow 4DF acquisition in the presence of moderate-intensity heart rate. 4) Seventy-seventy patients underwent cerebral diffusion-weighted MRI (DWI-MRI) at index visit. Of those, 50 patients underwent mitral valve surgery and subsequently a second cerebral MRI scan pre-discharge. SCI was defined as a new high-intensity lesion on the DWI-MRI. Findings - ix - 1) There was a significant association between pre-operative 4DF-CMR-derived MR volume and the post-operative left ventricular remodelling. 2) MR assessment by exercise-CMR is feasible and reproducible. 3) Although a clinically applicable 4DF-CMR pulse sequence during exercise was not fully developed, incremental improvements to pulse sequence were made such that the acquisition was possible during moderate-intensity exercise, with excellent quality images in 1 volunteer. 4) Silent cerebral infarction occurred in a third of patients undergoing mitral valve surgery for primary MR. There were no significant difference between the mitral valve repair and replacement techniques. SCI had no impact on patient quality of life, functional capacity or clinical outcomes.