Study population
This retrospective single-center cross-sectional study examined consecutive patients with MR who were scheduled for open surgical or transcatheter mitral valve repair at Osaka Metropolitan University Hospital between April 2014 and June 2019. All patients underwent two-dimensional transthoracic echocardiography (TTE) and 3D TEE before the procedure. Those with inadequate 3D TV visualization or moderate or severe aortic valve disease were excluded from analysis (n = 11). Informed consent was obtained using an opt-out approach in this study. The study protocol conformed to the ethical guidelines of the 1975 Declaration of Helsinki and the study protocol was approved by the Ethical Committee of Osaka City University Graduate School of Medicine (Approval Number: 2021-064).
Transthoracic Echocardiography Measurement
Comprehensive TTE was performed with one of the following systems using a high-frequency transducer: EPIQ CVx (Philips Medical Systems, Andover, MA, USA), iE33 (Phillips Medical Systems), Vivid E9 (GE Healthcare, Milwaukee, WI, USA), or Aplio 500 (Canon Medical Systems, Tochigi, Japan). Left ventricle end-diastolic diameter, left ventricular end-systolic diameter, interventricular septum thickness, and posterior wall thickness were measured according to 2017 European Society of Cardiology/European Association for Cardiothoracic Surgery guidelines [10]. Left atrial volume and left ventricular ejection fraction (LVEF) were evaluated using the biplane modified Simpson method; left atrial volume was indexed for body surface area [11]. The severity of MR was evaluated using a multiparametric approach that included assessment of the vena contracta, effective regurgitant orifice area (determined using the proximal isovelocity surface area method), and Doppler-derived regurgitant volume [12]. Severe MR was defined as effective regurgitant orifice area ≥ 0.40 cm2, regurgitant volume ≥ 60 mL, or regurgitant fraction ≥ 50% [7]. TR severity was evaluated using a multiparametric assessment of jet size, jet eccentricity, and vena contracta of the right ventricular (RV) inflow on parasternal short-axis and apical four-chamber views [13]. Significant TR was defined as moderate or severe TR. Peak TR jet velocity was measured from the cardiac apex. TR pressure gradient (TRPG) was calculated using the simplified Bernoulli equation and RV diameter was measured on an RV-focused four-chamber view at the base and mid-cavitary levels [14].
Three-dimensional Transesophageal Echocardiography Measurement
TEE was performed under intravenous propofol sedation with the iE33 or EPIQ CVx system (Philips Medical Systems, Andover, MA, USA) using a matrix-array transducer (X7-2t transducer and X8-2t transducer, Philips Medical Systems, Andover, Massachusetts, USA). Volume data sets were obtained using the live 3D zoom mode or 4-beat full-volume mode focused on the TV. Images were optimized for depth and gain settings before 3D acquisition. In patients with AF, live 3D zoom mode was selected to avoid stitch artifact and volume acquisition was performed for one beat [15]. All 3D TEE data were digitally stored for off-line analysis. TV parameters were acquired from the 3D reconstruction images of the TV annulus and analyzed using commercially available software (QLAB 3DQ and MVQ, Philips Medical Systems, Andover, MA, USA).
Analysis Of Tv Annulus And Leaflets And Morphology
3D data were displayed in the en face view with the interatrial septum positioned inferiorly (6 o'clock position), regardless of the orientation of the atria and ventricles (Fig. 1A) [16]. 3D parameters of the TV annulus were measured using QLAB mitral valve quantification software (QLAB MVQ, Philips Medical Systems, Andover, MA, USA). All three commissures between each three leaflets were detected (Fig. 1B). TA intercommissural distances, which are between the anteroseptal, anteroposterior, and posteroseptal commissures of the TV were also measured [9, 17, 18]. The distance between the anteroseptal and posteroseptal commissures, anteroseptal and anteroposterior commissures, and anteroposterior and posteroseptal commissures was defined as septal-leaflet length (SL), anterior-leaflet length (AL), and posterior-leaflet length (PL), respectively (Fig. 1C).
Statistical analysis
Continuous variables are expressed as medians with interquartile range. (IQR) and were compared using the unpaired t-test or Mann–Whitney U test as appropriate. Categorical variables are expressed as numbers with percentage and were compared using the χ2 test or Fisher’s exact test. Receiver operating characteristic (ROC) curve analysis was used to determine diagnostic performance of SL and PL for predicting significant TR. The appropriate cut-off value was selected to maximize the (sensitivity + [1 − specificity]) value. Inter- and intra-observer variabilities of 3D TEE annulus and distance measurements were evaluated by analysis of measurements in 20 random cases using the intraclass correlation coefficient. For interobserver variability, measurements were performed by two independent blinded observers; for intraobserver variability, measurements were performed by the same observer at two different time points. P < 0.05 was considered significant. Statistical analyses were performed using open source EZR software.