However, CMR SSFP - PC imaging examination is time consuming, requiring up to one hour of overall scan time. More recently, time-resolved phase contrast CMR with velocity encoding along all three flow directions and three-dimensional (3D) anatomic coverage (also termed ‘4D flow’) has been developed. CMR 4D flow imaging has the potential for a comprehensive morphofunctional cardiac evaluation reducing the overall scan time to 15 minutes even without contrast agents administration.
The purpose of this study was to compare CMR 4D flow and SSFP imaging for the assessment of MR severity using the degree of left ventricular (LV) remodeling after surgery as the reference standard.
METHODS: 10 consecutive patients (age: 59 ± 10) with indication to mitral valve plasty for severe mitral regurgitation were enrolled. MR severity was assessed using both CMR SSFP - PC imaging and CMR 4D flow imaging without the use of contrast agents. The pre-surgical estimate of regurgitant severity was correlated with the postoperative decrease in LV end-diastolic volume.
RESULTS: Agreement between CMR SSFP-PC imaging and CMR 4D flow imaging for MR regurgitant volume (RV) was excellent for both pre (r = 0.8, p<0.05, mean difference 5.1 mL) and post surgery (r= 0.9, p<0.05) evaluations. There was a strong correlation between post-surgical LV remodeling and MR severity as assessed by CMR 4D flow imaging (r=0.81, p <0.005) that was comparable to CMR SSFP-PC (r=0.78, p<0.005). The average time for MR assessment with CMR SSFP and PC imaging evaluation was 10 minutes, 2 minutes with CMR 4D flow imaging.
CONCLUSIONS: CMR 4D flow imaging without contrast agents allows an accurate and quick evaluation of MR regurgitant volume. There is a strong correlation between MR severity assessed with CMR 4D flow imaging and post-surgical LV remodeling. Indeed, CMR 4D flow imaging may represent an alternative method for MR severity assessment.