Sample size considerations and statistical analysis
ischemia, death, SD
REGRESSION, ISCHEMIA
Based on the nuclear sub study of the Clinical Outcomes Using Revascularization and Aggressive Drug Evaluation (COURAGE) trial, we anticipated that the average percentage of ischemic myocardium at follow-up imaging would be about 5% in either arm (SD ± 7%). Based on this, we estimated that a total sample size of 100 patients would provide over 95% power for a non-inferiority margin (delta) of 5% at a one-sided alpha of 2.5% (if the SD of the difference in % ischemic myocardium was 7 or lower). The primary analysis was a modified intention-to-treat analysis, which excluded patients who did not have the follow-up MPI (either due to death or loss to follow-up). No imputation was performed to account for missing data. Per-protocol analyses excluded patients who crossed over, and those in the ischemia-guided arm, who did not undergo baseline MPI. Since the mean difference in percent ischemia was not normally distributed, quantile regression was performed to compare the median percentage ischemia between the two arms. Bootstrapping with 50 repetitions was used to generate 95% confidence intervals. We inferred non-inferiority of ischemia-guided PCI over routine non-culprit PCI, if the upper limit of the 95% CI of this difference was < 5%. In a sensitivity analysis, we also used a generalised linear model using the gamma distribution with an identity link, to compute mean differences and the 95% CI. All analyses were adjusted for clinical site as a stratifying variable. Analyses were performed using Stata 17 (College Station, TX).