Prospective Longitudinal Study To Validate Accuracy Of The Global Anatomical Staging System (GLASS) Score In Predicting Major Acute Limb Events In Patients With Chronic Limb Threatening Ischemia Undergoing Endovascular Intervention

The Global Vascular Guideline (GVG) is an expert consensus, representing every major vascular society, aiming to promote a standardized evidence-based approach to assessing and treating patients with Chronic Limb Threatening Ischemia (CLTI). In terms of revascularization, the GVG recommendations revolve around three independent variables: patient risk, limb severity, and anatomic complexity (PLAN). Each section is fundamental to providing successful treatment to the patient, much controversy remains on which patterns of anatomical disease should be treated with endovascular or open surgery. To that end, the GLobal Anatomic Staging System (GLASS) was developed and adopted by the GVG committee as an angiographic scoring system to quantify the extent of infra-inguinal disease and predict the likely success of treatment with endovascular techniques (EVT).

GLASS is intended to predict the immediate technical success (ITS) and the 1-year limb base patency (LBP) after the EVT of the target artery pathway (TAP) and therefore aid in decision making. Currently there is no other risk prediction score or risk prediction model that estimates the probability of having ITS, LBP, major adverse limb events (MALE), major lower limb amputation (MLLA) and overall survival (OS) in patients presenting with CLTI who undergo EVT.

The purpose of this longitudinal prospective study is to examine the validity and reliability of the GLASS score in predicting ITS, LBP, MALE, MLLA, and OS in patients with CLTI, eventually helping to identify those patients who are likely to benefit from EVT. This could help clinicians make more informed decisions about treatment options, potentially reducing the need for more invasive procedures and improving patient outcomes. Additionally, the GLASS score could be used as a tool for patient selection in future clinical trials evaluating endovascular interventions for CLTI.

This study will follow a prospective observational study design. The study will initially be conducted within the Southeast Wales Vascular Network at Cardiff and Vale University Health Board. However, the study protocol allows for the inclusion of other hospitals or vascular units to participate in a collaborative model or as primary investigator sites, subject to obtaining necessary ethics approval and sponsorship agreement. The decision to involve additional sites will be made following a thorough evaluation by the research and development (R&D) committee. This approach will ensure compliance with ethical guidelines and regulatory requirements while also fostering potential collaboration and broadening the study's reach and generalizability.

Patients will be identified through routine clinic referrals and emergency presentations with CLTI; only patients who are referred for EVT will be recruited. Recruited patients will consent to access to their medical files and radiological data (duplex scans and angiography images) and a clinical follow-up up to one year. Standard care pathways are followed beyond this point. Outcome data will be collected from patients' medical files and interventional radiology reports immediately after the EVT and from vascular surgery clinic follow-up notes over a 12 months period. Symptom scores, admissions records, clinical and imaging data will be analysed at the end of follow-up to validate risk prediction. This will be supported by the European Vascular Research Collaborative (EVRC).