The Predictive Value of the Peripheral Arterial Calcium Scoring System on Computed Tomography Angiography in Patients With Chronic Limb-Threatening Ischemia Undergoing Below-the-Knee Endovascular Interventions

Introduction: Endovascular below-the-knee (BTK) revascularization is safe and effective in patients with chronic limb-threatening ischemia (CLTI), but outcomes depend on the severity of limb ischemia, anatomical pattern, comorbidity, and degree of vessel calcification. The most commonly used peripheral calcification score, the peripheral arterial calcium scoring system (PACSS), is angiography based and is therefore limited by low sensitivity and interobserver agreement. This study aimed to determine the prognostic value of the original and a modified PACSS (mPACSS) based on computed tomography angiography (CTA) imaging on short-term outcomes after BTK endovascular interventions. Materials and Methods: All consecutive patients included in the prospective Dutch Chronic Lower Limb-Threatening Ischemia Registry (THRILLER) between February 2021 and July 2023 who underwent CTA imaging within 6 months before the procedure were included. The mPACSS also takes calcification of the entire target vessel into account. Primary outcomes were limb salvage and amputation-free survival (AFS) at 3 months. Secondary outcomes were technical success, primary patency, and overall survival. Results: In total, 419 patients with 473 limbs were included (mean age 74.1 ± 10.2 years; 71.1% male). PACSS 4 was present in 39.7% of the limbs and associated with higher age and higher rates of hypertension, diabetes mellitus, cardiovascular morbidity, wound, ischemia, foot infection stage, global limb anatomic staging system stage and use of stents. In multivariable analysis, PACSS 4 was significantly associated with lower limb salvage (hazard ratio HR 2.75, 95% confidence intervals CI 1.49-5.08, P = .001) and AFS (HR 1.64, 95% CI 1.07-2.53, P = .025), as was mPACSS ≥5 (limb salvage: HR 2.22, 95% CI 1.88-5.46, P = .015; AFS: HR 1.68, 95% CI 1.06-2.65, P = .026). No significant differences were found in terms of technical success, primary patency, and overall survival. Conclusion: Both PACSS and mPACSS scored on CTA imaging are significantly associated with 3-month limb salvage and AFS after BTK endovascular interventions. Clinical Impact Current peripheral calcification scores are based on angiography and limited by a low sensitivity and minimal interobserver agreement. Scoring the original and modified peripheral arterial calcium scoring system (mPACSS) on computed tomography angiography (CTA) has proven to be more reliable and fast. Accordingly, this study shows that both PACSS and mPACSS scored on CTA are independent predictors of 3-month outcomes after below-the-knee interventions. This reinforces the importance of using a reliable peripheral calcification score in the preoperative assessment of CLTI patients eligible for revascularization. Future evaluations in larger cohorts with longer follow-up should investigate the PACSS and mPACSS in different clinical contexts and whether either score is superior.