Trajectory-Based Phenotyping After Coronary Artery Bypass Surgery

This is a single-center retrospective observational cohort study designed to evaluate the prognostic relevance of early postoperative trajectory-based biological phenotyping in adult patients undergoing elective coronary artery bypass grafting with cardiopulmonary bypass.

The study population will include patients operated between January 1, 2022 and December 31, 2025. Data will be obtained retrospectively from hospital information systems, electronic medical records, laboratory databases, and archived patient files. All data will be anonymized before analysis, and no patient-identifying information will be included in the study dataset.

The study will collect demographic characteristics, comorbidities, preoperative clinical variables, EuroSCORE II, perioperative variables such as cardiopulmonary bypass time and aortic cross-clamp time, and laboratory parameters. Early postoperative laboratory values from postoperative day 0 and postoperative day 1 will be used to calculate inflammatory and metabolic indices, including neutrophil-to-lymphocyte ratio, systemic immune-inflammation index, and triglyceride-glucose index. Serum creatinine changes will be used to evaluate renal response and postoperative acute kidney injury.

Patients will be classified into phenotypic subgroups using unsupervised clustering methods based on early postoperative biomarker trajectories. The clinical characteristics and outcomes of these subgroups will then be compared. The main outcomes of interest are postoperative acute kidney injury and prolonged intensive care unit stay. Additional analyses will assess whether phenotype classification improves risk stratification beyond EuroSCORE II.

The study does not involve any intervention, experimental treatment, additional laboratory testing, or change in clinical care. All analyses will be performed using previously recorded clinical and laboratory data.