This is a prospective, multicenter, non-inferior, parallel-controlled observational study. This study aims to compare clinical outcomes of endovascular treatment for acute high-risk type B aortic dissection in the acute phase versus the subacute phase. No interventions will be imposed on the patients' standard treatment. Patients with acute high-risk type B aortic dissection will be grouped based on the actual timing of their treatment.

Inclusion Criteria:

• Acute (2-14 days) high-risk type B aortic dissection.
• Completion of thoracoabdominal aortic CTA before enrollment.
• Ability to understand the study objectives and voluntarily participate, with signed informed consent from the patient or their legal representative.
• Willingness and ability to comply with follow-up visits and study protocols.

Exclusion Criteria:

• Acute complicated type B aortic dissection.
• Traumatic dissection or penetrating aortic ulcer.
• Connective tissue diseases (e.g., Marfan syndrome, Loeys-Dietz syndrome, Ehlers-Danlos syndrome).
• Pregnancy, women of childbearing potential, or breastfeeding.
• Uncontrolled active infection or active vasculitis.
• Unsuitable access vessels or infection at the access site.
• Endovascular repair requiring ≥2 branch reconstructions.
• Prior aortic surgery (open or endovascular).
• Life expectancy <2 years.
• Myocardial infarction or cerebrovascular accident within 4 weeks before enrollment.
• Severe gastrointestinal bleeding, major surgery, myocardial infarction, or uncorrected coagulation dysfunction within 6 weeks before enrollment.
• Other conditions deemed by the investigator to compromise the patient's medical interests or unlikely adherence to the study protocol.

Acute (2-14 days) high-risk type B aortic dissection (defined by one or more of the following: aortic maximum diameter >40 mm, primary tear on the lesser curvature, false lumen diameter >22 mm, entry tear >10 mm, aortic diameter growth >5 mm during hospitalization, imaging evidence of visceral malperfusion, haemorrhagic pleural effusion, need for readmission, or recurrent chest pain).