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.