Preparing for Bundled Payments: Impact of Complications Post-Coronary Artery Bypass Grafting on Costs.

Background: Bundled payments for coronary artery bypass grafting (CABG) provide a single reimbursement for care provided from admission through 90 days post-discharge. We aim to explore the impact of complications on total institutional costs, as well as the drivers of high costs for index hospitalization.

Methods: We linked clinical and internal cost data for patients undergoing CABG from 2014 to 2017 at a single institution. We compared unadjusted average variable direct costs, reporting excess cost from an uncomplicated baseline. We stratified by The Society of Thoracic Surgeons preoperative risk and quality outcome measures as well as value-based outcomes (readmission, post-acute care utilization). We performed multivariable linear regression to evaluate drivers of high costs, adjusting for preoperative and intraoperative characteristics and postoperative complications.

Results: We reviewed 1789 patients undergoing CABG with an average of 2.7 vessels (SD 0.89). A significant proportion of patients were diabetic (51.2%) and obese (mean body mass index 30.6, SD 6.1). Factors associated with increased adjusted costs were preoperative renal failure (P = .001), diabetes (P = .001) and body mass index (P = .05), and postoperative stroke (P < .001), prolonged ventilation (P < .001), rebleeding requiring reoperation (P < .001) and renal failure (P < .001) with varying magnitude. Preoperative ejection fraction and insurance status were not associated with increased adjusted costs.

Conclusions: Preoperative characteristics had less of an impact on costs post-CABG than postoperative complications. Postoperative complications vary in their impact on internal costs, with reoperation, stroke, and renal failure having the greatest impact. In preparation for bundled payments, hospitals should focus on understanding and preventing drivers of high cost.