Association Between Preoperative Ankle-Brachial Index and Postoperative Renal Adverse Events in Patients With Acute Stanford Type A Aortic Dissection: A Single-Center Retrospective Cohort Study

This is a single-centre retrospective observational cohort study using routinely collected electronic health records from adults undergoing emergency open repair of acute type A aortic dissection at Nanjing First Hospital, Nanjing Medical University, between January 2019 and February 2024. No study-specific intervention, treatment allocation, or additional clinical follow-up was performed.

The principal exposure was preoperative cuff-derived ankle-brachial index (ABI). ABI was calculated from routine four-limb oscillometric cuff pressures. Each ankle systolic pressure was divided by the higher brachial systolic pressure, and the higher of the two side-specific ABI values was used for patient classification. High ABI was defined as >1.40, and the reference ABI range was defined as >0.90 and ≤1.40. ABI was considered an indirect vascular phenotype marker rather than a direct measure of arterial stiffness or renal autoregulatory reserve.

The primary outcome was postoperative acute kidney injury (AKI) within 7 days, defined using serum creatinine-based Kidney Disease: Improving Global Outcomes criteria. Multivariable regression models were used to evaluate the association between high ABI and postoperative AKI after adjustment for relevant clinical and operative covariates.

Exploratory analyses assessed whether the association between cumulative intraoperative mean arterial pressure (MAP) burden and postoperative AKI differed according to ABI phenotype. Cumulative MAP burden below 65 and 80 mm Hg was evaluated. The candidate haemodynamic thresholds were informed in part by preliminary data exploration; these interaction analyses were therefore considered hypothesis-generating and were not intended to identify physiological or treatment thresholds.