Grading mitral regurgitation using 4D flow CMR: Comparison to transthoracic echocardiography.

OBJECTIVES: To determine the 4D Flow Cardiac Magnetic Resonance (CMR) thresholds that achieve the best agreement with transthoracic echocardiography (TTE) for grading mitral regurgitation (MR). METHODS: We conducted a single-center prospective study of patients evaluated for chronic primary MR in 2016-2020. MR was evaluated blindly by TTE and 4D Flow CMR, respectively by two cardiologists and two radiologists with decades of experience. MR was graded with both methods as mild, moderate, or severe. 4D Flow CMR measurements included MR regurgitant volume per beat (RV) and mitral anterograde flow per beat (MF). RF was obtained as the ratio RV/MF. Additionally, MF was compared to left ventricular stroke volume (LVSV) by cine-CMR. RESULTS: We included 33 patients in the initial cohort and 33 in the validation cohort. Inter-observer agreement was excellent for 4D Flow CMR ICC = .94 (95% CI, .86-.97, p < 0.0001). Using recommended TTE thresholds (30 ml, 60 ml, 30%, 50%), agreement was moderate for RV and RF. The best agreement between 4D Flow CMR and TTE was obtained with CMR thresholds of 20 and 40 ml for RV (κ = .93; 95% CI, .8-1) and 20% and 37% for RF (κ = .90; 95% CI, .7-.9). In the validation cohort, agreement between TTE and 4D Flow CMR was good with the optimal thresholds (κ = .78; 95% CI, .61-.94). CONCLUSION: We propose CMR thresholds that provide a good agreement between TTE and CMR for grading MR. Further studies are needed to fully validate 4D-Flow CMR accuracy for primary MR quantification.

4D flow cardiac magnetic resonance in children and adults with congenital heart disease: Clinical experience in a high volume center.

BACKGROUND: Cardiac magnetic resonance (CMR) imaging with velocity encoding along all three directions of flow, known as 4DFlow CMR, provides both anatomical and functional information. Few data are available on the usefulness of 4DFlow CMR in everyday practice. Here, our objective was to investigate the usefulness of 4DFlow CMR for assessing congenital heart disease (CHD) in everyday practice. METHODS: From 2017 to 2019, consecutive patients who underwent 4DFlow CMR were included prospectively at a single high-volume centre. The parameters recommended by an expert's consensus statement for each diagnosis (congenital valvulopathy, septal defect, complex CHD, tetralogy of Fallot, aortic abnormalities) were assessed by two blinded experienced readers. 4DFlow CMRs that provided all recommended parameters were considered successful. Inter-observer and intra-observer agreement were investigated. RESULTS: We included 187 adults and 60 children covering broad ranges of weight (4.5-142 kg) and age (0.1-67 years). 4DFlow CMR was always the second-line imaging modality, after inconclusive echocardiography, and was successful in 231/247 (91%) patients, with no significant difference between children and adults (54/60, 90%; and 177/187, 95%; respectively; p = .13). Longer time using 4DFlow CMR at our centre was associated with success; in children, older age was also associated with exam success. There was an about 12-month learning curve in children. The success rate was lowest in neonates. Inter-observer and intra-observer agreement were substantial. CONCLUSION: Our results suggest that 4DFlow CMR usually provides a comprehensive assessment of CHD in adults and children. A learning curve exists for children and the investigation remains challenging in neonates.