2.3 Statistical Analysis
Categorical variables were expressed as frequencies and percentages.
Continuous variables were expressed as the mean ± standard deviation.
The Fisher exact test was used to compare categorical variables, and the
Student’s t-test or the Mann-Whitney U-test was used to compare
continuous variables. Overall survival and freedom from death from heart
failure were analyzed using the Kaplan-Meier method. The log-rank test
was used for intergroup comparisons.
Backward stepwise Cox proportional hazards regression analysis was used
to determine the effect of perioperative variables on late mortality and
death from heart failure. The variables analyzed included age, sex, BSA,
the New York Heart Association (NYHA) 3/4, hypertension, diabetes,
ischemic heart disease, pulmonary hypertension, chronic obstructive
pulmonary disease, atrial fibrillation, cerebrovascular disease, chronic
kidney disease (serum creatinine >1.5 mg/dL), hemodialysis,
peripheral artery disease, prior cardiac surgery, preoperative left
ventricular (LV) ejection fraction (EF), postoperative LA diameter,
postoperative LV diastolic diameter, serum albumin, serum hemoglobin,
endocarditis/prosthetic valve endocarditis (PVE), emergency and PPM at
discharge. Variables showing P < .20 on univariable
analysis were subjected to multivariable Cox proportional hazards
regression analysis.
All statistical analyses were performed using the SPSS software version
25 (IBM Corp., Armonk, NY, USA). A P value < .05 was
considered statistically significant.