Clinical Utility of Infrapopliteal Calcium Score for the Evaluation of Severity of Peripheral Artery Disease.

ABSTRACT

PURPOSE: To identify associations between computed tomography (CT)-based lower-extremity calcium score (LECS) across different anatomic segments and the presence, severity, and clinical outcomes of peripheral artery disease (PAD). MATERIALS AND METHODS: In a mixed retrospective and prospective cohort study, 139 patients without prior lower-extremity intervention who underwent CT angiography of the aorta and lower extremities were identified. Subjects were classified as asymptomatic, claudicants, or having chronic limb-threatening ischemia (CLTI). LECS was measured using the Agatston method. Univariate and multivariate analyses were performed across categories of PAD severity. Receiver operating characteristic (ROC) analysis was performed, and an optimal cutoff point for LECS was identified. Claudicants were followed prospectively for CLTI and mortality. RESULTS: Higher infrapopliteal calcium score (CS) was independently associated with CLTI versus claudication (odds ratio [OR], 3.24 per unit increase in log10-transformed CS; P < .001) in addition to hemodialysis dependence and poor functional status. One hundred eighty-eight Agatston units was identified as the optimal cutoff for infrapopliteal CS in assessing the risk of CLTI versus claudication (area under the ROC curve, 0.84 [SD ± 0.049]). This cutoff was validated in an independent cohort to be associated with progression to CLTI (OR, 12.8; P = .0039). In the claudicant group followed prospectively, infrapopliteal CS ≥188 predicted increased risk of CLTI or death after adjusting for functional status and hemodialysis dependence (Cox hazard ratio, 4.92; P = .0202). CONCLUSIONS: Higher infrapopliteal CS was associated with CLTI among those with symptomatic PAD. An infrapopliteal CS cutoff of 188 Agatston units may serve as a useful tool to identify patients with increased risk of CLTI and mortality.