Statistical analysis
All analyses were performed using the STATA software (StataCorp, TX, USA). All extracted data are summarized as mean (±SD) and number (percentage). All values were concomitantly presented with 95% confidence interval (CI). Median values for continuous variables were converted into mean values.3 The weighted prevalence of endpoints during follow-up was calculated using the random-effects model and was presented as forest plots. To estimate the percentage of variation across studies, the Cochrane Q test was calculated and reported as the I2 statistic. The I2 value was classified into low heterogeneity (I2 = 25% to 49%), moderate heterogeneity (I2 = 50% to 74%), or high heterogeneity (I2>75%).4 To address heterogeneities, subgroup analyses using the Z-test were conducted. The test compared groups for estimation of the subgroup effect sizes and subgroup effects on heterogeneity. A meta-regression analysis was also conducted to find the potential effects of variables (i.e., age, gender, hypothermic circulatory arrest time, and the chronicity of surgery) on the pooled outcome. Publication bias was also estimated via the funnel plot visual inspection and the Begg’s test.