Statistical Analysis
Statistical analyses were performed using RStudio version 1.2.1335 (RStudio, Inc). Patient characteristics and reoperation rates (event rates) were compared using χ2 or Fischer’s Exact Test where appropriate. Time-dependent comparison of reoperation-free survival was demonstrated using Kaplan-Meier Survival curves with 95% log-log confidence intervals. The survival curves were log-inverted to demonstrate cumulative hazard of reoperation. The patient population was analysed as a whole and in subgroups based on age, sex, and current smoker status. A Cox-Proportionality Hazard Model comparing age, sex, current smoker status, and valve brand, but no interactions, was developed to determine Hazard Ratios of the variables. Competing risk analysis due to patient mortality was not performed due to lack of patient mortality data.