Standard and emerging CMR methods for mitral regurgitation quantification

Background: There are several methods to quantify mitral regurgitation (MR) by cardiovascular magnetic resonance (CMR). The interoperability of these methods and their reproducibility remains undetermined. Objective: To determine the agreement and reproducibility of different MR quantification methods by CMR across all aetiologies. Methods: Thirty-five patients with MR were recruited (primary MR = 12, secondary MR = 10 and MVR = 13). Patients underwent CMR, including cines and four-dimensional flow (4D flow). Four methods were evaluated: MR _Standard (left ventricular stroke volume - aortic forward flow by phase contrast), MR _LVRV (left ventricular stroke volume - right ventricular stroke volume), MR _Jet (direct jet quantification by 4D flow) and MR _MVAV (mitral forward flow by 4D flow - aortic forward flow by 4D flow). For all cases and MR types, 520 MR volumes were recorded by these 4 methods for intra−/inter-observer tests. Results: In primary MR, MR _MVAV and MR _LVRV were comparable to MR _Standard (P > 0.05). MR _Jet resulted in significantly higher MR volumes when compared to MR _Standard (P < 0.05) In secondary MR and MVR cases, all methods were comparable. In intra-observer tests, MR _MVAV demonstrated least bias with best limits of agreement (bias = −0.1 ml, −8 ml to 7.8 ml, P = 0.9) and best concordance correlation coefficient (CCC = 0.96, P < 0.01). In inter-observer tests, for primary MR and MVR, least bias and highest CCC were observed for MR _MVAV. For secondary MR, bias was lowest for MR _Jet (−0.1 ml, P[dbnd]NS). Conclusion: CMR methods of MR quantification demonstrate agreement in secondary MR and MVR. In primary MR, this was not observed. Across all types of MR, MR _MVAV quantification demonstrated the highest reproducibility and consistency.