Methods
Settings and Patient population
Institutional electronic medical records from a tertiary care center in
the United States were queried for patients who had mitral valve surgery
for mitral regurgitation (MR) caused degenerative mitral valve disease
between January 2011 and December 2016. Patients with MR due to
pathology other than degenerative (endocarditis, hypertrophic
obstructive cardiomyopathy, ischemic, and functional MR) were excluded
from the analysis. Patient demographics, baseline characteristics, and
other risk factors were recorded. Operative reports were reviewed by a
research resident (S.Y.) trained by the senior author (A.G.). Mortality
data were retrieved from the hospital electronic record system on the
date of censoring (02/22/2020). Of note: hospital mortality data is
updated monthly from the Connecticut state vital statistics which
captures subjects who died within the state. The Institutional Review
Board at Yale University approved this study. IRB protocol ID:
2000020356, approval date: 2/13/2019. Need for written patient consent
was waived by the IRB.
Definitions
Experienced surgeon was defined as a surgeon who performed an average of
≥25 mitral valve surgeries/year (all mitral valve pathologies)
throughout the study period, surgeons with <25 were defined as
less experienced8. Valve pathology was defined
according to leaflet involvement (posterior leaflet, anterior leaflet or
bi-leaflet prolapse). Residual MR was defined as mild MR or less on
intraoperative transthoracic echocardiogram (ECHO) at end of operation.
Repair complexity was defined by a technical score summing the number of
techniques used in the repair: Simple repairs used only a single
technique, moderate repairs used 2-4, and complex repairs used 5 or
more9. Recurrent MR was defined as moderate or higher
MR on any follow-up ECHO.
Outcomes
The primary outcome of the study was successful valve repair versus
replacement. Secondary outcomes included recurrent MR, reoperation for
recurrence, and mortality.
Statistical analysis
Differences in patient characteristics according to surgeon experience
were compared with two-tailed t-tests for continuous variables and
Fisher’s exact tests for categorical variables. Multivariable logistic
regression analysis was performed to identify independent risk factors
for MR recurrence by 2-year follow-up. Survival analysis for mortality
was performed with Kaplan-Meier curve and Cox proportional hazard model.
To identify variables to be included in the model, we first compared
patients who died to patients who were still alive on the day of
censoring and variables with P values ≤0.02 were included in the model.
These variables are patient’s age at the time of surgery, surgeon
experience, valve replacement vs repair, hypertension, dyslipidemia,
diabetes mellitus (DM), atrial fibrillation, congestive heart failure
(CHF), chronic lung disease, and urgent/emergent operation. P value of
<0.05 and 95% confidence interval (CI) were used to define
statistically significant differences. Analyses were conducted using
Microsoft Excel 2019 and Prism 8.2 (GraphPad Software, San Diego, CA),
and SAS 9.4 (SAS Institute Inc, Cary, NC).