4D Flow Cardiac MR in Primary Mitral Regurgitation

Abstract

BackgroundFour‐dimensional‐flow cardiac MR (4DF‐MR) offers advantages in primary mitral regurgitation. The relationship between 4DF‐MR‐derived mitral regurgitant volume (MR‐Rvol) and the post‐operative left ventricular (LV) reverse remodeling has not yet been established.PurposeTo ascertain if the 4DF‐MR‐derived MR‐Rvol correlates with the LV reverse remodeling in primary mitral regurgitation.Study TypeProspective, single‐center, two arm, interventional vs. nonintervention observational study.PopulationForty‐four patients (male N = 30; median age 68 [59–75]) with at least moderate primary mitral regurgitation; either awaiting mitral valve surgery (repair [MVr], replacement [MVR]) or undergoing “watchful waiting” (WW).Field Strength/Sequence5 T/Balanced steady‐state free precession (bSSFP) sequence/Phase contrast imaging/Multishot echo‐planar imaging pulse sequence (five shots).AssessmentPatients underwent transthoracic echocardiography (TTE), phase‐contrast MR (PMRI), 4DF‐MR and 6‐minute walk test (6MWT) at baseline, and a follow‐up PMRI and 6MWT at 6 months. MR‐Rvol was quantified by PMRI, 4DF‐MR, and TTE by one observer. The pre‐operative MR‐Rvol was correlated with the post‐operative decrease in the LV end‐diastolic volume index (LVEDVi).Statistical TestsIncluded Student t‐test/Mann–Whitney test/Fisher's exact test, Bland–Altman plots, linear regression analysis and receiver operating characteristic curves. Statistical significance was defined as P < 0.05.ResultsWhile Bland–Altman plots demonstrated similar bias between all the modalities, the limits of agreement were narrower between 4DF‐MR and PMRI (bias 15; limits of agreement −36 mL to 65 mL), than between 4DF‐MR and TTE (bias −8; limits of agreement −106 mL to 90 mL) and PMRI and TTE (bias −23; limits of agreement −105 mL to 59 mL). Linear regression analysis demonstrated a significant association between the MR‐Rvol and the post‐operative decrease in the LVEDVi, when the MR‐Rvol was quantified by PMRI and 4DF‐MR, but not by TTE (P = 0.73). 4DF‐MR demonstrated the best diagnostic performance for reduction in the post‐operative LVEDVi with the largest area under the curve (4DF‐MR 0.83; vs. PMRI 0.78; and TTE 0.51; P = 0.89).Data ConclusionThis study demonstrates the potential clinical utility of 4DF‐MR in the assessment of primary mitral regurgitation.Evidence Level2Technical EfficacyStage 5