Table 3.

Relevant published studies in contemporary practice focusing on the volumetric method by echocardiography to quantify primary MR.

First author, year (Ref #)	Number of patients	Comparative method	Main findings
Cawley et al., 2013 (129)	26 with primary MR in sinus rhythm	–CMR volumetric method	–Good correlation between RegVol assessed by 2D-TTE versus CMR volumetric methods (r = 0.79). –Under-estimation of LV volumes assessed by 2D-TTE compared with CMR
Maréchaux et al., 2014 (130)	60 with primary MR due to prolapse (all grades) in sinus rhythm	–MR 4-grades 1+ to 4+ integrated approach	–High feasibility for determining 3D-TTE RegFrac (90% of patients) –Highly specific cut-off value of 3D-TTE RegFrac ≥ 40% to detect significant MR (3+ or 4+) –Large overlap zone for 3D-TTE RegFrac between 3 + and 4+ MR grades –Better discriminative value of 3D-TTE compared with 2D-TTE RegFrac between 1 and 2+ vs. 3–4+ MR grades
Heo et al., 2017 (131)	–37 (validation group out of 152) who underwent CMR with primary (n = 27) or secondary (n = 10) MR (all grades)	–RegFrac by CMR volumetric method	–Moderate correlation (r = 0.53) with poor agreement (−75; 40 ml) between RegVol assessed by 2D-TTE versus CMR volumetric methods.
Levy et al., 2018 (132)	–53 with primary MR due to prolapse (all grades)	–RegVol by CMR volumetric and 2D-PISA methods	–High feasibility (86% of patients) for determining 3D-TTE RegVol using automated fast 3D-TTE software (HeartModel) –Excellent inter- and intraobserver reproducibility for RegVol between 3D-TTE and CMR volumetric methods (56 ± 28 ml vs. 57 ± 23 ml) but significantly higher using 2D-PISA (69 ± 30 ml)
Lee et al., 2018 (133)	–166 with severe primary MR due to chordae rupture in sinus rhythm	–RegVol by 2D-PISA	–Discordant MR severity grading found in 41% of patients using RegVol (>60 ml by 2D-PISA but < 60 ml by 2D-TTE volumetric method) –Moderate correlation (r = 0.53) with poor agreement (−25; 162 ml) between RegVol assessed by 2D-TTE volumetric versus 2D-PISA methods. –Small LV EDV or narrow PISA angle associated with over-estimation of RegVol by PISA versus 2D-TTE volumetric methods.
Altes et al., 2022 (134)	–188 with moderate-to-severe or severe primary MR due to prolapse in sinus rhythm	–RegVol by 2D-PISA and CMR volumetric methods	–Weak correlation (r = 0.30) with poor agreement (–37; 63 ml) between RegVol assessed by 2D-TTE volumetric versus 2D-PISA methods. –Moderate correlation (r = 0.55) between RegVol assessed by 2D-TTE versus CMR volumetric methods –Fair correlation between LVEDV and RegVol (r = 0.68) but not RegFrac (r = 0.17) assessed by 2D-TTE volumetric methods