High-risk percutaneous coronary intervention with or without mechanical circulatory support: Will Impella show superiority in the PROTECT IV randomized trial?

Background: PROTECT IV is a current enrolling randomized controlled trial evaluating high-risk percutaneous coronary intervention (HR-PCI) with prophylactic Impella versus no Impella to reduce the composite primary endpoint of all-cause death, stroke, myocardial infarction (MI), or cardiovascular hospitalization. In a PROTECT IV-like cohort of patients who underwent HR-PCI without Impella, we aimed to report the rate of major adverse events to determine whether the trial is adequately powered. Methods and results: A total of 700 patients meeting similar inclusion/exclusion criteria of PROTECT IV who underwent HR-PCI without Impella at a single tertiary center from 2008 to 2022 were included in the analysis. The composite rates of all-cause death, MI, target lesion revascularization, and target vessel revascularization at 1, 2, and 3 years were estimated using the Kaplan-Meier method, and the results were used to calculate the sample size under the constant hazard ratio assumption and expected number of events to be observed used in planning PROTECT IV. The primary endpoint occurred in 30.8 % of patients at 2 years. PROTECT IV assumes a hazard ratio of 0.75 using a multivariate Cox regression, which, under a 5 % level and 90 % power, yields 516 events. This implies a 2-year primary outcome rate of 50 % for the non-Impella arm. Conclusion: Therefore, PROTECT IV estimates that a sample size of 1252 patients is required for Impella to be declared superior to the non-Impella group. Using our observed 2-year outcome of 30.8 %, we estimate that PROTECT IV requires 1966 patients, demonstrating that PROTECT IV is probably underpowered.