GLASS differs from current scoring systems as it focuses on outlining a target artery pathway (TAP) individually for each patient and requires selection of the preferred infrapopliteal artery for treatment to improve limb and foot perfusion. The GLASS was designed to be utilised using invasive DSA¹. MRA produces images of a similar quality to DSA with the absence of ionizing radiation exposure or the need for iodine contrast, therefore reducing the likelihood of nephropathy². A meta-analysis compared MRA with CTA and DUS and findings showed an increase in both sensitivity and specificity in MRA³. The aim of our study was to assess and directly compare MRA vs DSA for scoring CLTI patients with GLASS and further to assess if MRA can predict amputation free survival (AFS) for patients with CLTI.

This is a prospective analysis of retrospectively collected data. The study population consisted of the first 50 patients who have had lower limb angioplasty as first intervention in our unit in 2014. Our inclusion criteria were patients with CLTI who have had MRA and had infrainguinal disease and subsequently went onto DSA and endovascular intervention. MRAs were used to give patients a GLASS stage and then this was compared directly with stage on DSA in a blinded fashion. This data was further investigated to look at the mortality, AFS and limb-based patency (LBP) after the intervention. For statistical analysis Excel and SPSS software were used.

The dataset included 231 patients who had undergone a lower limb angiography in 2014. 181 patients were excluded. 50 patients (Age range 36- 95, mean 75) were analysed further, of which 66% were male (n=33) and 34% were female (n=17). 12 patients underwent major amputation, with an average of 377.5 days between initial intervention and amputation. The amputation free survival (AFS), the number of days from intervention to either death or major amputation, had an average of 1195.7 days across the 50 patients. 7 patients did not live beyond 1-year post-intervention. The 1 year LBP, defined as primary patency of the entire target artery pathway (TAP) for 1 year⁴, was 51.2% (n=22) for the remaining 43 patients. Using MRA, 5, 19 and 26 patients were assigned GLASS grades I, II and III, respectively. Within the GLASS stage I cohort, all of the patients survived, 4 (80%) of the patients had successful 1 year LBPs and 1 (20%) did not. 1 patient had a major amputation. Out of the 19 patients assigned a GLASS stage II, 1 had died and within 1 year of intervention. From the remaining 18 patients, 10 (56%) of the patients had 1 year LBP and 8 did not (44%). 4 patients underwent major amputation. In the GLASS III group, 4 (15.4%) patients survived and 22 had died (84.6%), 6 of which were within a year of initial intervention. From the 20 patients that lived longer than a year, 8 (40%) patients had 1 year LBP and 12 (60%) did not. 6 patients underwent major amputation. The average AFS for stages I, II and II was 1789, 1492 and 865 days, respectively. The LBPs of 80%, 56% and 40% for stages I, II and III from MRA, respectively, are in line with the predicted LBP from GLASS in the Global Vascular Guidelines (GVG)¹. The same group of patients were assigned GLASS stages using DSA and 10, 14 and 26 patients were assigned GLASS stages I, II and III, respectively. The GLASS stages assigned via MRA and DSA were compared and 70% (n=35) of patients had matching stages. 30% (n=15) of patients did not have matching scores, of which 6 were found to have higher scores from DSA and 9 found to have lower scores from DSA.

This investigation shows that GLASS can be scored with success with MRA, without exposure to radiation/nephrotoxic contract and arterial access. Stages assigned using MRA were 70% consistent with those assigned using DSA. LBP data was consistent with limits suggested in the GVG GLASS guidelines.

1. Conte MS, Bradbury AW, Kolh P, White J V, Committee S, Dick F, et al. CLINICAL PRACTICE GUIDELINE DOCUMENT Global Vascular Guidelines on the Management of Chronic Limb-Threatening Ischemia Eur J Vasc Endovasc Surg (xxxx) xxx, xxx. Eur J Vasc Endovasc Surg [Internet]. 2019 [cited 2022 Apr 10]; Available from: https://doi.org/10.1016/j.ejvs.2019.05.006. 2. Collins R, Burch J, Cranny G, Aguiar-Ibáñez R, Craig D, Wright K, et al. Duplex ultrasonography, magnetic resonance angiography, and computed tomography angiography for diagnosis and assessment of symptomatic, lower limb peripheral arterial disease: systematic review. [cited 2022 Apr 11]; Available from: http://www.bmj.com/ 3. Menke J, Larsen J. Meta-analysis: Accuracy of contrast-enhanced magnetic resonance angiography for assessing steno-occlusions in peripheral arterial disease. Ann Intern Med. 2010 Sep 7;153(5):325-34. 4. Khoury R El, Wu B, Kupiec-Weglinski S, Liu IH, Edwards C, Lancaster E, et al. Limb-Based Patency Defines Effective Revascularization for Chronic Limb-Threatening Ischemia. J Vasc Surg [Internet]. 2021 Sep 1 [cited 2022 Apr 11];74(3):e248-9. Available from: http://www.jvascsurg.org/article/S0741521421013641/fulltext