Statistical Analysis
Pre-operative covariates were assessed for normal distribution using the
Shapiro-Wilk test. Between group characteristics were assessed for
statistical differences using the Student T-test or Wilcoxon Rank Test
for non-parametric variables. Differences in discrete data was assessed
using Pearson’s χ2 test. Multivariate logistic
regression models were constructed to assess the influence of a variety
of covariates on a composite end-point (moderate/severe aortic
regurgitation, reintervention on the aortic root or valve and
mortality).
Crude survival curves were estimated using the nonparametric
Kaplan-Meier method, and log rank tests were used to compare the
survival distribution among groups. Cox proportional hazard regression
was conducted to calculate the adjusted hazards ratio with 95%
confidence intervals. Stepwise selection was performed using age, sex,
COPD, Euroscore, NYHA class and LV function in the model. Statistical
analyses were conducted using the Stata 13.0 software (Stata Corp.,
College Station, TX, USA).