The Global Vascular Guideline on chronic limb threatening ischemia (CLTI) proposes the Global Limb Anatomic Staging System (GLASS), a new angiographic scoring system to quantify the anatomic severity of infrainguinal disease in CLTI patients. However, GLASS validation still needs to be completed, and the infrapopliteal (IP) target artery pathway (TAP) was easily influenced by the procedures. Thus the IP target artery could be selected either as the least diseased artery based on angiography or prospectively based on the angiosome concept. So the investigators aim to evaluate its correlation with clinical outcomes after revascularization.

The Global Vascular Guideline on chronic limb threatening ischemia (CLTI) recommends using the Global Limb Anatomic Staging System (GLASS) to assess the severity of infrainguinal disease in CLTI patients. GLASS staging involves scoring the femoropopliteal (FP) and infrapopliteal (IP) segments separately. For IP segment scoring, the target artery path (TAP) is identified by the clinician based on either the least diseased or the recanalized IP path. However, this approach may lead to diverse GLASS staging results, especially for simple lesions below the knee. Additionally, the current version of GLASS does not account for multivessel IP revascularization, which may introduce subjective bias if a physician chooses different IP targets during multiple revascularization procedures.

In order to improve our understanding of the current staging system, the investigators will establish a prospective registry that collects data on conservative patients who have Chronic Limb-Threatening Ischemia (CLTI) and undergo endovascular therapy for infrainguinal lesions. To evaluate the stage of the lesions, the investigators will use two distinct IP scoring techniques. One approach will be based on the least disease IP path as identified by the pre-interventional angiogram, while the second technique will be based on the recanalized IP path preferred by the clinician. This scoring will be carried out by experienced physicians and the results will be recorded in an electronic database. Then the correlation between the major adverse limb events (such as clinical-driven target limb revascularization, major amputation, and all-cause death) with the patient's Wound, Ischemia, foot Infection (WIFI) classification, GLASS anatomic staging, calcification severity, and modified Society for Vascular Surgery (SVS) run-off score will be analyzed.

Inclusion Criteria:

1. Clinical diagnosis of chronic limb-threatening ischemia (CLTI)
2. Undergo endovascular therapy for infrainguinal lesions

Exclusion Criteria:

1. Pregnant women or female patients with potential childbearing
2. Patients who have acute limb thromboembolism or require thrombectomy during the procedure
3. Untreated inflow disease of the ipsilateral pelvic arteries (more than 50% stenosis or occlusion)
4. Patients with known allergy to contrast media

Patients with infrainguinal lesions suffering from critical limb-threatening ischemia