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).