This retrospective cohort study will evaluate whether a high preoperative ankle-brachial index is associated with postoperative renal adverse events in patients with acute Stanford type A aortic dissection who underwent surgical repair. The ankle-brachial index is a noninvasive vascular measurement that may reflect arterial stiffness and vascular calcification. A high ankle-brachial index may indicate abnormal vascular aging and impaired vascular compliance.

The study will use existing clinical data from patients treated at Nanjing First Hospital, Nanjing Medical University, between January 2021 and February 2024. No intervention will be assigned as part of this study. The primary aim is to examine the association between a preoperative ankle-brachial index of 1.4 or higher and the risk of acute kidney injury within 7 days after surgery.

Acute Stanford type A aortic dissection is a life-threatening cardiovascular emergency that usually requires urgent surgical repair. Postoperative acute kidney injury is a common and clinically important complication after surgery for acute type A aortic dissection and is associated with worse short-term and long-term outcomes. Identification of preoperative vascular markers associated with postoperative renal adverse events may help improve perioperative risk stratification.

The ankle-brachial index is a simple, noninvasive measure calculated from systolic blood pressure measured at the ankle and arm. Although a low ankle-brachial index is commonly used to identify peripheral artery disease, an abnormally high ankle-brachial index, usually defined as 1.4 or higher, may reflect noncompressible arteries, medial arterial calcification, and increased arterial stiffness. These vascular abnormalities may be associated with impaired renal perfusion reserve and increased susceptibility to kidney injury after major cardiovascular surgery.

This is a single-center, retrospective observational cohort study. The study will include patients with acute Stanford type A aortic dissection who underwent surgical repair at Nanjing First Hospital, Nanjing Medical University, from January 2021 to February 2024. Clinical data will be obtained from existing medical records. No study-specific intervention, treatment allocation, or additional follow-up will be performed.

The main exposure is preoperative ankle-brachial index. Patients will be categorized according to whether they have a high ankle-brachial index, defined as an ankle-brachial index of 1.4 or higher. The primary outcome is postoperative acute kidney injury within 7 days after surgery. Renal outcomes will be assessed using routinely collected perioperative clinical and laboratory data.

The study will compare baseline characteristics, perioperative variables, and postoperative renal outcomes between patients with and without a high preoperative ankle-brachial index. Multivariable regression models will be used to evaluate the association between high ankle-brachial index and postoperative renal adverse events after adjustment for relevant clinical covariates. Additional analyses may assess the association between ankle-brachial index and the severity of postoperative renal injury, as well as the robustness of the findings in sensitivity analyses.

Inclusion Criteria:

1. Patients diagnosed with acute Stanford type A aortic dissection.
2. Patients who underwent surgical repair for acute Stanford type A aortic dissection at Nanjing First Hospital, Nanjing Medical University, between January 2021 and February 2024.
3. Patients aged 18 years or older.
4. Patients with available preoperative ankle-brachial index data.
5. Patients with available perioperative renal function data for assessment of postoperative renal outcomes.

Exclusion Criteria:

1. Patients younger than 18 years.
2. Patients without available preoperative ankle-brachial index data.
3. Patients without sufficient perioperative serum creatinine data to assess postoperative acute kidney injury.
4. Patients with preoperative end-stage renal disease or maintenance dialysis.
5. Patients with incomplete key clinical data required for the main analysis.

The study population will include adult patients with acute Stanford type A aortic dissection who underwent surgical repair at Nanjing First Hospital, Nanjing Medical University, between January 2021 and February 2024. Eligible patients will be identified from existing hospital medical records. Patients will be included if preoperative ankle-brachial index data and perioperative renal function data are available.

Individual participant data will not be shared because this retrospective study uses existing hospital medical records containing sensitive clinical information. Data sharing is restricted by institutional policies and privacy considerations. De-identified aggregate results may be made available in the publication or from the corresponding author upon reasonable request, subject to institutional approval.