Validating GLASS Score in Predicting Acute Limb Events in CLTI Patients

Ischemia is a severe medical condition that occurs when the blood and oxygen supply to a specific part of the body is significantly reduced or completely absent, it can affect any body part, often the legs. It is typically caused by the narrowing or blockage of an artery and can result in severe pain, tissue gangrene, and the potential loss of a limb (Amputation). This condition requires medical intervention and will not improve on its own.

To diagnose leg ischemia, the doctor will conduct a thorough vascular clinical examination. Depending on the findings, further imaging tests such as duplex ultrasound, magnetic resonance arteriography (MRA), or computed tomography (CT) may be conducted. In some cases, an arteriogram may be necessary which is an x-ray of the arteries while the dye is injected into the blood vessels.

Following the diagnosis, the best management course is recommended by a multidisciplinary team (MDT), considering each patient's disease pattern and overall health. Treatment options include performing a key-hole procedure, called an endovascular procedure (EVT) within the artery, where the vascular surgeon will be using a balloon to widen the artery, and/or a wire-reinforced stent which remains inside the artery serving as a scaffolding to keep it open.

The primary aim of the PROMOTE GLASS study is to investigate if the Global Anatomical Staging System (GLASS) score, which is a summation of points given according to the disease pattern as seen on assessment images (Duplex Ultrasound, MRA, and CT scans) can accurately tell if the treatment using catheters and stents inside blood vessels will work well for people with ischemia in their legs. The researchers also want to see if the GLASS score can predict how well patients with ischemia will heal and if they will need further treatments in the long term after having treatment with catheters and stents inside their blood vessels.

A prospective, observational study will be delivered by Cardiff and Vale University Health Board (CAVUHB). The vascular team will prospectively collect data over a 12-month period. This will be in patients undergoing elective and/or emergency primary EVT procedure, with follow-up 4-6 weeks after the procedure and at 12 months.

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).

This study will be supervised by the Chief Investigator, Mr. Lewis Meecham (Consultant Vascular and Endovascular Surgeon) and sponsored by Cardiff and Vale University Health Board. An internal management group consisting of clinicians, researchers and managerial staff will be established to oversee and monitor the progress of the study. The management group will meet on a monthly basis to raise, discuss, and resolve any issues arising during the conduct of the study.

Eligibility Criteria:
Inclusion Criteria:

1. Patients with peripheral vascular disease (PVD) under investigation for CLTI
2. Age 18 years or older
3. Able to consent to inclusion.

Exclusion Criteria:

1. Patient with traumatic or iatrogenic lesions leading to CLTI.
2. Acute Limb Ischemia (symptoms for \<2 weeks)
3. Patients who have undergone open/endovascular revascularization of the same limb within the last 12 months
4. Patients who present with inflow disease (Common iliac artery (CIA), External Iliac Artery (EIA), and Common Femoral artery (CFA) disease) not intended for treatment during the same admission or prior to recruitment.
5. Palliative revascularization (for pain in end of life)
6. Patient with expected problems of maintaining a 1-year follow-up (e.g., no fixed address)
7. Patients with previously implanted devices (stents) within the affected segment