Patient characteristics and echocardiographic data were collected from the medical records and echocardiography reports. The study protocol was approved by the Institutional Review Board of New Tokyo Hospital and was in accordance with the guidelines of the Declaration of Helsinki. The requirement for informed consent was waived because of the retrospective nature of this study. Based on integrative methods using qualitative, semiquantitative, and quantitative approaches, 154 patients with at least mild SMR were identified via a review of echocardiography databases at New Tokyo Hospital between January 2018 and March 2021. These patients underwent 3D-TEE based on clinical indications and transthoracic echocardiography (TTE) within 1 month of 3D-TEE at our center [4]. SMR was defined as incomplete mitral leaflet closure because of regional myocardial dysfunction, global left ventricular remodeling, apical tethering of the mitral valve (MV), or annular dilation in the presence of an anatomically normal valve apparatus [4, 13]. Of 172 patients, those with multiple or nonholosystolic SMR jet (6 patients), previous MV intervention (7 patients), concomitant mitral stenosis (2 patients) [14], and mitral annular calcification (3 patients) were excluded from this study.

Overall, 19 of 154 patients were excluded because the quality of 3D imaging was inadequate for VCA${}_{\text{3D}}$ analysis, and 7 patients were excluded because of incomplete data for the quantitative assessment of SMR; hence, 128 patients were included in the final analysis.

Echocardiographic examinations were performed using iE33 system (Philips Healthcare, Andover, MA, USA) and EPIQ7 system (Philips Healthcare, Andover, MA, USA) equipped with a matrix-array transducer for transthoracic (X5-1) and transesophageal echocardiography (X7-2t and X8-2t), according to the guidelines for the clinical application of echocardiography [4, 14, 15, 16, 17, 18]. For offline analysis, echocardiographic data were stored in a computer at a dedicated workstation.

Regarding two-dimensional TTE (2D-TTE) parameters, left ventricular end-diastolic and -systolic volumes, left ventricular ejection fraction (LVEF), and left atrial volume were estimated using the biplane Simpson disk method via transthoracic echocardiography.

Regarding TEE parameters, EROA${}_{\text{PISA}}$ and regurgitant volume (RV${}_{\text{PISA}}$) were estimated using the proximal isovelocity surface area method [4]. A continuous wave Doppler cursor was aligned parallel to the SMR jet for obtaining peak velocity and velocity–time integral at a Nyquist limit of 50–70 cm/s, with the gain set to a level immediately below the threshold for noise. EROA${}_{\text{PISA}}$ was derived using a color Doppler in a four-chamber view at an aliasing velocity of 30–40 cm/s. Moreover, during systole, proximal isovelocity surface area (PISA) radius and flow velocity parameters were obtained at similar time points for calculating EROA${}_{\text{PISA}}$. To determine VC parameters, 3D color Doppler datasets were acquired from an intercommissural view using full volume for each patient. The quantification of VCA${}_{\text{3D}}$ was performed via multiplanar reconstruction using dedicated software (Philips QLAB Versions 9.0, Philips Healthcare, Andover, MA, USA) (Fig. 1) [4]. The cropping plane was moved along the direction of the jet until the smallest jet cross-sectional area became visible at the level of VC. Subsequently, VCA${}_{\text{3D}}$ was measured using manual planimetry of the color Doppler flow signal. VCW${}_{\text{AP}}$ and VCW${}_{\text{ML}}$ were also measured as anteroposterior and mediolateral VCWs, respectively, in reconstructed 2D planes from the 3D-TEE dataset; VCW${}_{\text{AP}}$ and VCW${}_{\text{ML}}$ were obtained in the left ventricular outflow tract and intercommissural views (or views that were close to intercommissural views), respectively [8]. VCW${}_{\text{Average}}$ was calculated as (VCW${}_{\text{AP}}$ + VCW${}_{\text{ML}}$)/2, VCA${}_{\text{Ellipse}}$ was calculated as $\pi$ $\times$ (VCW${}_{\text{AP}}$/2) $\times$ (VCW${}_{\text{ML}}$/2) [8], and VCA${}_{\text{3D}}$ shape index was calculated as VCW${}_{\text{ML}}$/VCW${}_{\text{AP}}$. In patients with irregular rhythm (i.e., atrial fibrillation or flutter not requiring constant ventricular pacing for bradycardia), these parameters were calculated as the mean of 3–5 parameters performed by avoiding remarkable irregular RR intervals. EROA${}_{\text{PISA}}$ and VC parameters were performed by one observer (H.O.).

Fig. 1.

Assessment of vena contracta using 3D-TEE. A case of an 84-year-old woman with dilated cardiomyopathy and secondary mitral regurgitation. (A) Vena contracta described by multiplanar reconstruction of 3D color Doppler datasets. (B) VCA${}_{\text{3D}}$ measured using manual planimetry of the vena contracta was 0.42 cm${}^2$. VCW${}_{\text{AP}}$ and VCA${}_{\text{ML}}$ measured as the narrow and wide VCWs in the anteroposterior and mediolateral directions were 0.43 and 1.21 cm, respectively. VCW${}_{\text{Average}}$, calculated as (VCW${}_{\text{AP}}$ + VCW${}_{\text{ML}}$)/2, was 0.82 cm. VCA${}_{\text{Ellipse}}$, calculated as $\pi$ $\times$ (VCW${}_{\text{AP}}$/2) $\times$ (VCW${}_{\text{ML}}$/2), was 0.41 cm${}^2$. IC, intercommissural; LVOT, left ventricular outflow tract; 3D-TEE, three-dimensional transesophageal echocardiography; VCA${}_{\text{3D}}$, three-dimensional vena contracta area; VCW${}_{\text{AP}}$, anteroposterior vena contracta width; VCW${}_{\text{ML}}$, mediolateral vena contracta width; VCW${}_{\text{Average}}$, average of anteroposterior and mediolateral vena contracta widths; VCA${}_{\text{Ellipse}}$, vena contracta area as an ellipse.

VCA${}_{\text{3D}}$ of $\ge$0.39 cm${}^2$ was used as a reference standard of severe SMR in the current study, considering that the severity of SMR may be underestimated using EROA${}_{\text{PISA}}$ and that VCA${}_{\text{3D}}$ is a more robust parameter for distinguishing severe SMR than EROA${}_{\text{PISA}}$ [4, 11].

Categorical variables were presented as frequencies and analyzed using chi-square, Fisher’s exact, or Cochran–Armitage test, as appropriate. Continuous variables were presented as mean $\pm$ standard deviation or median with interquartile range and were compared using Mann–Whitney U or Jonckheere–Terpstra test, as appropriate. The overall rates of correct SMR severity classifications based on VCA${}_{\text{3D}}$ were statistically compared using McNemar’s test in 2 $\times$ 2 tables. Correlations between different parameters were determined using Pearson’s test and linear regression analysis. Receiver operating characteristic (ROC) curve analyses were performed to assess the ability of each parameter to identify severe SMR based on VCA${}_{\text{3D}}$. The Youden index was used to determine the best cutoff value for severe SMR based on VCA${}_{\text{3D}}$ considering optimal sensitivity and specificity. Discrimination of severe SMR based on VCA${}_{\text{3D}}$ was assessed using the C-statistic. All statistical tests were two-tailed, and a two-sided p-value of 0.05 was considered to indicate statistical significance. Data analysis was performed using EZR software version 1.50 (Saitama Medical Center, Jichi Medical University, Saitama, Japan) [19].

The mean age of the patients was 77.0 $\pm$ 8.9 years, and 78 (60.9%) patients were men (Table 1). Regarding echocardiographic data, the mean LVEF was 37.5% $\pm$ 13.4%, with an LVEF of 50% in 95 (74.2%) patients (Table 2). The mean tenting height of MV was 0.88 $\pm$ 0.34 cm. Regarding SMR quantification, EROA${}_{\text{PISA}}$ and RV${}_{\text{PISA}}$ were 0.26 $\pm$ 0.12 cm${}^2$ and 40.6 $\pm$ 17.3 mL, respectively, with severe SMR based on EROA${}_{\text{PISA}}$ of $\ge$0.40 cm${}^2$ (according to the current guidelines) in 16 (12.5%) patients [4]. VCA${}_{\text{3D}}$ was 0.46 $\pm$ 0.26 cm${}^2$, with severe SMR based on VCA${}_{\text{3D}}$ in 75 (58.6%) patients. VCW${}_{\text{Average}}$ and VCA${}_{\text{Ellipse}}$ were 0.84 $\pm$ 0.26 cm and 0.49 $\pm$ 0.28 cm${}^2$, respectively.

EROA${}_{\text{PISA}}$ showed a strong correlation with VCA${}_{\text{3D}}$ (r = 0.801, p 0.001) (Fig. 2A). ROC curve analysis revealed that EROA${}_{\text{PISA}}$ showed good discrimination of severe SMR based on VCA${}_{\text{3D}}$ (C-statistic, 0.910; 95% confidence interval [CI], 0.859–0.961; p 0.001), with the best cutoff value of 0.21 cm${}^2$ (Fig. 2B). The sensitivity and specificity of EROA${}_{\text{PISA}}$ for severe SMR based on VCA${}_{\text{3D}}$ were as follows: EROA${}_{\text{PISA}}$ of 0.20 cm${}^2$, 92.0% and 73.6%; EROA${}_{\text{PISA}}$ of 0.30 cm${}^2$, 49.3% and 94.3%; and EROA${}_{\text{PISA}}$ of 0.40 cm${}^2$, 22.6% and 100.0%; respectively. In addition, VCA${}_{\text{3D}}$ and SMR incidence were significantly lower (p 0.001) in patients with nonsevere SMR based on EROA${}_{\text{PISA}}$ of 0.40 cm${}^2$ (according to the current guidelines) than in those with severe SMR based on EROA${}_{\text{PISA}}$ of $\ge$0.40 cm${}^2$ (Fig. 2C,D) [4]. Notably, among 112 patients with nonsevere SMR based on EROA${}_{\text{PISA}}$ of 0.40 cm${}^2$, 59 (52.7%) had discordantly severe SMR based on VCA${}_{\text{3D}}$. SMR severity based on VCA${}_{\text{3D}}$ was not correctly reclassified as severe SMR by EROA${}_{\text{PISA}}$ (McNemar’s test; p 0.001).

Fig. 2.

Associations of VCA${}_{\text{𝟑𝐃}}$ with EROA${}_{\text{𝐏𝐈𝐒𝐀}}$. (A) Correlations between VCA${}_{\text{3D}}$ and EROA${}_{\text{PISA}}$. (B) Receiver operating characteristic curve analyses of EROA${}_{\text{PISA}}$ to identify severe SMR. (C) Comparison of VCA${}_{\text{3D}}$ between the nonsevere (EROA${}_{\text{PISA}}$ of 0.40 cm${}^2$) and severe (EROA${}_{\text{PISA}}$ of $\ge$0.40 cm${}^2$) SMR groups. (D) Incidence of severe SMR based on VCA${}_{\text{3D}}$ of $\ge$0.39 cm${}^2$ in the nonsevere (EROA${}_{\text{PISA}}$ of 0.40 cm${}^2$) and severe (EROA${}_{\text{PISA}}$ of $\ge$0.40 cm${}^2$) SMR groups. VCA${}_{\text{3D}}$, three-dimensional vena contracta area; EROA${}_{\text{PISA}}$, effective regurgitant orifice area by proximal isovelocity surface area method; SMR, secondary mitral regurgitation.

VCW${}_{\text{AP}}$ showed a strong correlation with VCA${}_{\text{3D}}$ (r = 0.786, p 0.001). ROC curve analysis indicated that VCW${}_{\text{AP}}$ showed relatively good discrimination of severe SMR based on VCA${}_{\text{3D}}$ (C-statistic, 0.874; 95% CI, 0.812–0.936; p 0.001), with the best cutoff value of 0.43 cm.

VCW${}_{\text{Average}}$ and VCA${}_{\text{Ellipse}}$ had a strong correlation with VCA${}_{\text{3D}}$ (r = 0.940, p 0.001 and r = 0.980, p 0.001, respectively) (Figs. 3A,4A). According to ROC curve analysis, VCW${}_{\text{Average}}$ and VCA${}_{\text{Ellipse}}$ showed fairly good discrimination of severe SMR based on VCA${}_{\text{3D}}$ (C-statistic, 0.981; 95% CI, 0.963–1.000; p 0.001 and C-statistic, 0.985; 95% CI, 0.970–1.000; p 0.001, respectively), with the best cutoff values of 0.78 cm and 0.42 cm${}^2$, respectively (Figs. 3B,4B). Moreover, regarding the comparison of C-statistics, VCW${}_{\text{Average}}$ and VCA${}_{\text{Ellipse}}$ showed significantly better discrimination than EROA${}_{\text{PISA}}$ (p = 0.007 and p = 0.003, respectively).

Fig. 3.

Associations of VCA${}_{\text{𝟑𝐃}}$ with VCW${}_{\text{𝐀𝐯𝐞𝐫𝐚𝐠𝐞}}$. (A) Correlations between VCA${}_{\text{3D}}$ and VCW${}_{\text{Average}}$. (B) Receiver operating characteristic curve analyses of VCW${}_{\text{Average}}$ to identify severe SMR. (C) Comparison of VCA${}_{\text{3D}}$ between the nonsevere (VCW${}_{\text{Average}}$ of 0.78 cm) and severe (VCW${}_{\text{Average}}$ of $\ge$0.78 cm) SMR groups. (D) Incidence of severe SMR based on VCA${}_{\text{3D}}$ of $\ge$0.39 cm${}^2$ in the nonsevere (VCW${}_{\text{Average}}$ of 0.78 cm) and severe (VCW${}_{\text{Average}}$ of $\ge$0.78 cm) SMR groups. VCA${}_{\text{3D}}$, three-dimensional vena contracta area; VCW${}_{\text{Average}}$, average of anteroposterior and mediolateral vena contracta widths; SMR, secondary mitral regurgitation.

Fig. 4.

Associations of VCA${}_{\text{𝟑𝐃}}$ with VCA${}_{\text{𝐄𝐥𝐥𝐢𝐩𝐬𝐞}}$. (A) Correlations between VCA${}_{\text{3D}}$ and VCA${}_{\text{Ellipse}}$. (B) Receiver operating characteristic curve analyses of VCA${}_{\text{Ellipse}}$ to identify severe SMR. (C) Comparison of VCA${}_{\text{3D}}$ between the nonsevere (VCA${}_{\text{Ellipse}}$ of 0.42 cm${}^2$) and severe (VCA${}_{\text{Ellipse}}$ of $\ge$0.42 cm${}^2$) SMR groups. (D) Incidence of severe SMR based on VCA${}_{\text{3D}}$ of $\ge$0.39 cm${}^2$ in the nonsevere (VCA${}_{\text{Ellipse}}$ of 0.42 cm${}^2$) and severe (VCA${}_{\text{Ellipse}}$ of $\ge$0.42 cm${}^2$) SMR groups. VCA${}_{\text{3D}}$, three-dimensional vena contracta area; VCA${}_{\text{Ellipse}}$, vena contracta area as an ellipse; SMR, secondary mitral regurgitation.

In addition, patients with nonsevere SMR, according to VCW${}_{\text{Average}}$ of 0.78 cm and VCA${}_{\text{Ellipse}}$ of 0.42 cm${}^2$, showed significantly lower VCA${}_{\text{3D}}$ (p 0.001 for both) and SMR incidence based on VCA${}_{\text{3D}}$ (p 0.001 for both) than those with severe SMR based on VCW${}_{\text{Average}}$ and VCA${}_{\text{Ellipse}}$ (Fig. 3C,D and Fig. 4C,D). Notably, SMR severity based on VCA${}_{\text{3D}}$ was correctly reclassified as severe SMR based on VCW${}_{\text{Average}}$ (p = 0.505) and VCA${}_{\text{Ellipse}}$ (p = 0.182).

Our patients were classified into the following three subgroups based on EROA${}_{\text{PISA}}$ according to the current guidelines [4]: 88 patients with EROA${}_{\text{PISA}}$ of 0.30 cm${}^2$, 24 patients with EROA${}_{\text{PISA}}$ of 0.30–0.40 cm${}^2$, and 16 patients with EROA${}_{\text{PISA}}$ of $\ge$0.40 cm${}^2$. According to the incremental EROA${}_{\text{PISA}}$, VCA${}_{\text{3D}}$ (p 0.001) and SMR incidence based on VCA${}_{\text{3D}}$ (p 0.001) significantly increased (Fig. 5A,B). Notably, in patients with EROA${}_{\text{PISA}}$ of 0.30 cm${}^2$, which is suggestive of moderate SMR according to the current guidelines, 38 of 88 (43.2%) patients had severe MR based on VCA${}_{\text{3D}}$. However, SMR severity based on VCA${}_{\text{3D}}$ in patients with EROA${}_{\text{PISA}}$ of 0.30 cm${}^2$ was correctly reclassified as severe MR based on VCW${}_{\text{Average}}$ (p = 0.505) and VCA${}_{\text{Ellipse}}$ (p = 0.182) (Fig. 6A,B).

Fig. 5.

Associations between VCA${}_{\text{𝟑𝐃}}$ and EROA${}_{\text{𝐏𝐈𝐒𝐀}}$ among the three subgroups (EROA${}_{\text{𝐏𝐈𝐒𝐀}}$ of 0.30 cm${}^{\mathrm{2}}$, EROA${}_{\text{𝐏𝐈𝐒𝐀}}$ of 0.30–0.40 cm${}^{\mathrm{2}}$, and EROA${}_{\text{𝐏𝐈𝐒𝐀}}$ of $\mathrm{\ge }$0.40 cm${}^{\mathrm{2}}$). (A) Increase in VCA${}_{\text{3D}}$ according to the increase in SMR severity. (B) Incidence of severe SMR based on VCA${}_{\text{3D}}$ of $\ge$0.39 cm${}^2$ according to the increase in SMR severity. VCA${}_{\text{3D}}$, three-dimensional vena contracta area; EROA${}_{\text{PISA}}$, effective regurgitant orifice area by proximal isovelocity surface area method; SMR, secondary mitral regurgitation.

Fig. 6.

Associations of VCA${}_{\text{𝟑𝐃}}$ with VCW${}_{\text{𝐀𝐯𝐞𝐫𝐚𝐠𝐞}}$ and VCA${}_{\text{𝐄𝐥𝐥𝐢𝐩𝐬𝐞}}$ in the EROA${}_{\text{𝐏𝐈𝐒𝐀}}$ 0.30 cm${}^{\mathrm{2}}$ group. (A) Incidence of severe SMR based on VCA${}_{\text{3D}}$ of $\ge$0.39 cm${}^2$ between the nonsevere (VCW${}_{\text{Average}}$ of 0.78 cm) and severe (VCW${}_{\text{Average}}$ of $\ge$0.78 cm) SMR groups. (B) Incidence of severe SMR based on VCA${}_{\text{3D}}$ of $\ge$0.39 cm${}^2$ between the nonsevere (VCA${}_{\text{Ellipse}}$ of 0.42 cm${}^2$) and severe (VCA${}_{\text{Ellipse}}$ of $\ge$0.42 cm${}^2$) SMR groups. VCA${}_{\text{3D}}$, three-dimensional vena contracta area; VCW${}_{\text{Average}}$, average of anteroposterior and mediolateral vena contracta widths; VCA${}_{\text{Ellipse}}$, vena contracta area as an ellipse; EROA${}_{\text{PISA}}$, effective regurgitant orifice area determined by the proximal isovelocity surface area method; SMR, secondary mitral regurgitation.

Although VCW${}_{\text{AP}}$ was shown to be a reliable semiquantitative parameter for evaluating SMR severity according to the current guidelines, VCW${}_{\text{ML}}$ evaluation is not routinely used as a stand-alone parameter [4]. However, according to a previous study by Kahlert et al. [8], VCW${}_{\text{ML}}$ was more strongly correlated with VCA${}_{\text{3D}}$ than with VCW${}_{\text{AP}}$. Furthermore, VCW${}_{\text{Average}}$ is strongly correlated with VCA${}_{\text{3D}}$ [8]. To accurately identify severe SMR, the current guidelines recommend calculating VCW${}_{\text{Average}}$ with a cutoff value of 0.80 cm for severe SMR if the regurgitant orifice area is elliptical [4]. However, there is little information on the discrimination and best cutoff value of VCW${}_{\text{Average}}$ for severe SMR. Our study indicated that VCW${}_{\text{Average}}$ had a fairly strong correlation with VCA${}_{\text{3D}}$ and showed adequately good discrimination of severe SMR. Notably, the best cutoff value of VCW${}_{\text{Average}}$ was 0.78 cm—which is close to the value of 0.80 cm according to the current guidelines—with adequately high sensitivity and specificity for severe SMR based on VCA${}_{\text{3D}}$ [4]. Further, VCA${}_{\text{Ellipse}}$ had a strong correlation with VCA${}_{\text{3D}}$ and showed good discrimination of severe SMR. Moreover, the best cutoff value of VCA${}_{\text{Ellipse}}$ was 0.42 cm${}^2$, with high sensitivity and specificity for severe SMR based on VCA${}_{\text{3D}}$.

The current study and previous studies have demonstrated that the regurgitant orifice area in SMR may be elliptical [8, 12], indicating that SMR severity based on VCW${}_{\text{AP}}$ and EROA${}_{\text{PISA}}$ is underestimated [4, 5, 6]. Furthermore, there was a weak correlation between the VCA${}_{\text{3D}}$ shape index and difference between VCA${}_{\text{3D}}$ and EROA${}_{\text{PISA}}$; this finding conforms to that reported by Goebel et al. [11], suggesting that the ellipticity of the regurgitant orifice area rather than the extent of ellipticity is related to the underestimation of SMR severity based on EROA${}_{\text{PISA}}$.

Patients with SMR having EROA${}_{\text{PISA}}$ of 0.30 cm${}^2$, corresponding to moderate SMR according to the current guidelines, have a potential risk of underestimation of SMR severity because of the elliptical regurgitant orifice area [4]. Of the 88 patients with EROA${}_{\text{PISA}}$ of 0.30 cm${}^2$ in the current study, 38 (43.2%) had severe MR based on VCA${}_{\text{3D}}$. In such cases, VCW${}_{\text{Average}}$ of $\ge$0.78 cm and/or VCA${}_{\text{Ellipse}}$ of $\ge$0.42 cm${}^2$ might be useful in identifying discordantly severe SMR based on VCA${}_{\text{3D}}$. If EROA${}_{\text{PISA}}$ is $\ge$0.30 cm${}^2$, SMR severity is expected to be truly severe based on VCA${}_{\text{3D}}$; however, EROA${}_{\text{PISA}}$ of 0.30 cm${}^2$ does not necessarily indicate nonsevere SMR based on VCA${}_{\text{3D}}$. If VCW${}_{\text{Average}}$ of $\ge$0.78 cm and/or VCA${}_{\text{Ellipse}}$ of $\ge$0.42 cm${}^2$ are calculated using VCW${}_{\text{AP}}$ and VCW${}_{\text{ML}}$, SMR severity might be considered discordantly severe despite the EROA${}_{\text{PISA}}$ of 0.30 cm${}^2$. After the exclusion of severe SMR according to the abovementioned assessment, symptomatic patients may be evaluated using exercise-stress echocardiography to confirm significantly worsening SMR, if applicable.

Although severe SMR is associated with adverse clinical outcomes [1, 2, 3], it may be underestimated using conventional echocardiographic parameters, including VCW${}_{\text{AP}}$ and EROA${}_{\text{PISA}}$. Moreover, an inaccurate assessment of SMR severity can lead to misleading indications for optimal MV interventions, including MV transcatheter edge-to-edge repair, which is known to be effective and is recommended in patients with SMR with reduced LVEF [5, 20, 21]. Karam et al. [22] reported that MV transcatheter edge-to-edge repair for SMR is equally effective in patients with EROA${}_{\text{PISA}}$ of 0.30 cm${}^2$ and those with EROA${}_{\text{PISA}}$ of $\ge$0.30 cm${}^2$ in terms of clinical outcomes, suggesting that patients with EROA${}_{\text{PISA}}$ of 0.30 cm${}^2$ may have a higher severity of SMR than expected based on EROA${}_{\text{PISA}}$. To obtain an accurate evaluation of SMR severity, VCA${}_{\text{3D}}$ is useful as a substantially reliable echocardiographic parameter [11]. However, the assessment of VCA${}_{\text{3D}}$ is relatively time-consuming and requires good quality of 3D-echocardiographic data [4]. VCW${}_{\text{Average}}$ and VCA${}_{\text{Ellipse}}$, which were calculated via simple equations using VCW${}_{\text{AP}}$ and VCW${}_{\text{ML}}$, showed fairly strong correlations with VCA${}_{\text{3D}}$ and good discrimination of severe SMR based on VCA${}_{\text{3D}}$. Therefore, instead of VCA${}_{\text{3D}}$, VCW${}_{\text{Average}}$ and VCA${}_{\text{Ellipse}}$, with best cutoff values of 0.78 cm and 0.42 cm${}^2$, respectively, might be helpful in identifying true severe SMR.