An advantage of CMR compared with TTE is that because there is no limitation of imaging windows the CMR mapping protocol enabled a complete and systematic assessment of the mitral valve in every patient. Contiguous slices perpendicular to the valve closure line were consistently and easily obtained producing a standardised data set for interpretation. The very high inter- and intra-observer agreement obtained reflect this. Acquisition of the mapping images was efficient, requiring on average 7 cine images, and between 5 to 10 minutes per patient.
In patients with mitral valve prolapse, CMR has an established role in the assessment of LV size and function and mitral regurgitation severity. Wit
the addition of mitral valve mapping, CMR can potentially provide a comprehensive assessment of mitral regurgitation secondary to mitral valve prolapse in patients undergoing evaluation for valve surgery.
A limitation of this study is that a gold standard mapping assessment, either operative findings or TOE imaging, was available in only one third of patients. A larger study with surgical and/or TOE corroboration is required to assess the accuracy of CMR in segmental mapping of mitral valve leaflet pathology.
The study cohort comprised patients with known mitral valve prolapse with at least moderate mitral regurgitation on prior echocardiography. The ability of systematic CMR assessment of the mitral valve to detect mitral regurgitation jet lesions or leaflet abnormalities in patients with mild mitral regurgitation or other leaflet pathologies was not examined. The utility of CMR in the evaluation of mitral regurgitation in patients with atrial fibrillation was not assessed. These patients were excluded due to concern regarding reduced image quality due to the irregular rhythm. In addition to mapping of the abnormal segments, mitral valve leaflet length, the presence of mitral annular calcification and the assessment of sub-valvular structures are often important in assessing the ability to repair the mitral valve. These parameters were not formally assessed in this study. Whilst CMR is likely to be useful for assessment of mitral leaflet length and potentially the three-dimensional relationships between leaflets and subvalvular structures, the assessment of calcification by CMR is poor.
In patients with mitral regurgitation due to mitral valve prolapse, assessment of the mechanism of mitral regurgitation, jet direction and systematic valve mapping using a simple and efficient CMR protocol is feasible and should be considered as part of the standard CMR examination in patients with mitral regurgitation. Further studies are required to evaluate whether CMR valve mapping could be an alternative when preoperative TOE mapping is required.
TTE trans-thoracic echocardiogram, TOE trans-oesophageal echocardiogram, CMR Cardiovascular Magnetic Resonance, AMVL Anterior Mitral Valve Leaflet, PMVL Posterior Mitral Valve Leaflet
The author(s) declare that they have no competing interests.
The authors are grateful to Barbara Semb, Research Secretary, Green Lane Research and Education Fund, for secretarial assistance.
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