Preoperative Ankle-Brachial Index and Renal Adverse Events After Acute Type A Aortic Dissection Surgery

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.

Inclusion criteria

• Adults aged 18 years or older with acute type A aortic dissection.
• Underwent emergency open surgical repair at Nanjing First Hospital, Nanjing Medical University, between January 2019 and February 2024.
• Routine preoperative four-limb cuff pressure measurements sufficient for calculation of ABI.
• Postoperative serum creatinine measurements sufficient for ascertainment of AKI.

Exclusion criteria

• Non-standard or aborted repair, or insufficient intraoperative haemodynamic recordings for the planned analyses.
• Preoperative estimated glomerular filtration rate <30 ml min-1 1.73 m-2, maintenance dialysis, or end-stage kidney disease.
• Severe preoperative heart failure, defined as cardiogenic shock, mechanical circulatory support, left ventricular ejection fraction <30%, or New York Heart Association class IV.
• Previous peripheral or aortic intervention affecting ABI interpretation.
• Imaging-confirmed renal or limb malperfusion.
• ABI ≤0.90.
• For patients with more than one potentially eligible repair during the same admission, only the first eligible repair was included.