Cardiovascular Magnetic Resonance for Direct Assessment of Anatomic Regurgitant Orifice in Mitral Regurgitation

Abstract

Background— In patients with mitral regurgitation (MR), assessment of the severity of valvular dysfunction is crucial. Recently, regurgitant orifice area has been proposed as the most useful indicator of the severity of MR. The purpose of our study was to determine whether planimetry of the anatomic regurgitant orifice (ARO) in patients with MR is feasible by cardiovascular magnetic resonance (CMR) and correlates with invasive catheterization and echocardiography effective regurgitant orifice [ECHO-ERO] by proximal isovelocity surface area. Methods and Results— Planimetry of ARO was performed with a 1.5-T CMR scanner using a breath-hold balanced gradient echo sequence true fast imaging with steady state precession (TrueFISP). CMR planimetry of ARO was possible in 35 of 38 patients and was closely correlated with angiographic grading ( r =0.84, P <0.0001). In patients with MR grade ≥III on catheterization, CMR-ARO (0.60�0.29 cm 2 versus 0.30�0.19 cm 2 , P <0.0001) as well as ECHO-ERO (0.49�0.17 cm 2 versus 0.27�0.10 cm 2 ) were significantly elevated in comparison with MR grade <III. Further, CMR-ARO was closely correlated to CMR regurgitant fraction and volume ( r =0.90 and r =0.91, P <0.0001, respectively) and catheterization regurgitant fraction and volume ( r =0.86 and 0.83, P <0.0001, respectively). The correlation between CMR-ARO and ECHO-ERO was 0.81 ( P <0.0001) and CMR slightly overestimated ECHO-ERO by 0.06 cm 2 ( P <0.05). As assessed by receiver operating characteristic analysis, CMR-ARO at a threshold of 0.40 cm 2 detected MR grade ≥III as defined by catheterization, with a sensitivity and specificity of 94% and 94%, respectively. Conclusion— CMR planimetry of the anatomic mitral regurgitant lesion in patients with MR is feasible and permits quantification of MR with good agreement with the accepted invasive and noninvasive methods. Direct measurement by CMR is a promising new method for the precise assessment of ARO area and the severity of MR.