Gender disparities in rehospitalizations after coronary artery bypass grafting: evidence from a sparse functional causal mediation analysis of the MIMIC-IV data

Abstract Hospital readmissions following coronary artery bypass grafting (CABG) not only impose a substantial cost burden on healthcare systems but also serve as a potential indicator of the quality of medical care. Previous studies of gender effects on complications after CABG surgery have consistently revealed that women tend to suffer worse outcomes. To better understand the causal pathway from gender to the number of rehospitalizations, we study the postoperative central venous pressure (CVP), recorded over the first 24 hours of patients’ intensive care unit (ICU) stay after the CABG surgery, as sparse observations of a functional mediator. Confronted with time-varying CVP measurements and zero-inflated rehospitalization counts within 60 days following discharge, we propose a parameter-simulating quasi-Bayesian Monte Carlo approximation method that accommodates a sparse functional mediator and a zero-inflated count outcome for causal mediation analysis. Focusing on patients who would undergo CABG under either gender, we find a causal relationship between the female gender and increased rehospitalization counts after CABG, and that time-varying central venous pressure mediates this causal effect.