Methods
Patient population
We included seventy-seven consecutive patients who underwent TMVr using the MitraClip system at a single center in Asia from April 2018 to November 2019. Indications for TMVr included symptomatic, moderate-to-severe (3+), or severe (4+) MR(11) with a high risk for surgery. An interdisciplinary heart team, which included an interventional cardiologist, a cardiac surgeon, an echocardiologist, and a cardiac anesthetist, discussed each subject’s eligibility for TMVr. All patients gave written informed consent in a local registry to be included in the study. The protocol of this study was approved by the ethical committee of St. Marianna University School of Medicine.
Transthoracic echocardiographic measurement
Transthoracic echocardiography was performed at baseline (within a week prior to TMVr) and before discharge (shortly after TMVr). MR severity was defined as none or trace (0/4+), mild (1+/4+), moderate (2+/4+), moderate-to-severe (3+/4+), and severe (4+/4+) using the American Society of Echocardiography (ASE) guidelines for an integrative approach.(12,13) Systolic pulmonary artery (PA) pressure was calculated from the peak tricuspid regurgitant (TR) jet velocity using the simplified Bernoulli’s equation, with the addition of the right atrial pressure estimated from inferior vena cava diameter.(14) TR quantification, as well as the evaluation of RV dimensions and function, was performed according to the recommendations of the ASE guidelines.(11,14) Briefly, RV function was assessed through tricuspid annular plane systolic excursion (TAPSE) acquired on M-mode tracings through the tricuspid annulus by the RV-focused apical 4-chamber view (Figure1). RV fractional area change (FAC) by the apical 4-chamber view is the area difference between RV end-diastolic and end-systolic areas measured through ideally RV-focused apical view. RV systolic excursion velocity (S’) was defined by tissue Doppler echocardiography as a parameter of the longitudinal velocity of the tricuspid annulus.(15)
Clinical follow-up
Clinical outcome was defined as the presence or absence of cardiovascular (CV) events, which included cardiovascular death and hospitalization for heart failure (HF). HF was defined as dyspnea and objective signs consistent with New York Heart Association (NYHA) class II–IV requiring hospitalization and medication. Clinical follow-up data were obtained by review of medical records.
Statistical analysis
Data are expressed as median and interquartile range (IQR) for continuous variables and number and percentage for categorical variables. The t -test was used to determine between-group differences for continuous variables, and the chi-squared test was used to determine between-group differences for categorical variables. We tested the ability of TAPSE to predict CV events by evaluating the area under the curve (AUC) of its receiver operating characteristic (ROC) curve, and compared its AUC with those of FAC and RV S’. Event-free curves were generated using the Kaplan-Meier method. Log-rank tests were used to evaluate the differences between groups. Multivariate cox regression analysis was used to ascertain the relationship between clinical and echocardiographic variables, which could indicate a potential relationship with outcomes. The results of cox regression analysis are given as hazard ratios (HR) with their respective 95% confidence intervals (CIs). A probability value of less than 0.05 was considered to indicate statistical significance. Analysis was conducted using a standard statistical software program (SPSS version 19, IBM Corp., Armonk, NY, USA).