Statistical Analysis
Statistical analysis was performed using SPSS Statistics 25.0 (IBM SPSS Statistics for Windows, Version 25.0, Armonk, NY).
Since both surgical procedures were performed consecutively over time yielding only a limited time overlap during the learning phase of MIVT, this study is inherently biased. Therefore, a propensity-score matched analysis with a tolerance of 0.05 and without replacement was executed for the patient characteristics having a baseline significant difference. Adjustment was performed for differences in preoperative NYHA class and previous cardiac surgery to match both study groups.
Data distribution is verified for normality by the Shapiro-Wilk test. Categorical variables are expressed by number and percentage. Continuous variables are noted as mean and standard deviation or as median and interquartile range, depending on the distribution normality of the data. Categorical variables were compared between groups by Chi-square or Fisher’s exact test. Comparison of continuous data was done by the unpaired t-test or Mann-Whitney U-test.
To examine significant between-group differences in biomarker evolution over time points, an repeated ANOVA-analysis was used. Significance was based on Wilk’s-Lambda or Greenfeld-Houser testing depending on Mauchly’s sphericity preservation of the data. Survival analysis was performed by the Kaplan–Meier estimation method with log-rank testing of the difference between both procedures. All tests were performed 2-tailed and considered as statistically significant for a p-value < 0.05.