Beyond the 30-day metric: National trends and predictors of 90-day readmission after coronary artery bypass grafting

Study objective: Evaluate the national burden, predictors, and causes of 90-day readmission following coronary artery bypass grafting (CABG), and to examine temporal trends and demographic disparities in readmission risk. Design: Retrospective cohort study. Setting: United States hospitals participating in the Nationwide Readmissions Database. Participants: Adult patients (≥18 years) undergoing isolated CABG between 2016 and 2022 were identified using ICD-10 codes. Patients who died during the index hospitalization, underwent concomitant valve surgery were excluded. Main outcome measures: The primary outcome was all-cause 90-day readmission. Secondary outcomes included 30-day readmission, in-hospital complications, and causes of 90-day readmission. Results: Among 681,833 patients undergoing isolated CABG, 111,024 (16.3%) were readmitted within 90 days; notably, 36% occurred between 31 and 90 days after discharge. Heart failure was the leading cause of readmission (13.6%), followed by infection (6.7%), coronary artery disease-related diagnoses (6.7%), and atrial fibrillation (4.1%). Readmitted patients had higher rates of perioperative complications, including acute renal failure (28% vs 17%), respiratory failure (26% vs 17%), pneumonia (7% vs 3%), and transfusion (18% vs 12%). Independent predictors included female sex (adjusted odds ratio [aOR] 1.38), age ≥ 85 years (aOR 1.27), congestive heart failure (aOR 1.46), diabetes with complications (aOR 1.38), peripheral vascular disease (aOR 1.39), chronic kidney disease (aOR 1.30), and chronic obstructive pulmonary disease (aOR 1.34). Risk-adjusted readmission rates remained consistently higher among women across all age groups, with age-related patterns differing by sex. Conclusion: Our findings suggest that reliance on 30-day metrics may underestimate postoperative morbidity and highlight opportunities for extended post-discharge surveillance and complication prevention.