Abstract 722: Evaluation of Peripheral Calcium Score as a Measure of Peripheral Artery Disease Severity

Abstract

The current gold standard for diagnosing PAD is Ankle Brachial Index (ABI). However, vascular calcification can falsely elevate ABI. No studies have compared the diagnostic value of peripheral calcium score (PCS) in lower extremity arteries with ABI. Primary aim of this study was to describe the association of PCS with continuous ABI values and categories of ABI in a retrospective cohort design. We identified 50 patients who underwent CTA and ABI measurements [ABI categories for PAD severity: severe (<0.5), moderate (0.5-0.9), normal (0.9-1.4), noncompressible (>1.4)]. We evaluated CTAs imaged from abdominal aorta through lower extremities and determined total calcium volume of plaques with density >130 HU and area >1mm 2 from infrarenal abdominal aorta to the foot using TeraRecon by two independent readers (Intra class correlation 99%). We explored the association between ABI and PCS in SAS using multiple linear regression and analysis of covariance adjusting for age, race, smoking status, hypertension, hyperlipidemia, type II diabetes, and chronic kidney disease. We found that ABI was inversely associated with PCS in linear regression (p<0.01, Figure 1A). Differences in mean PCS were statistically significant across ABI categories [F(3,29)= 5.03, p=0.01, Figure 1B]. Across subgroups, the mean PCS was significantly different for ABIs <0.5 and 0.5-0.9 (p=0.02), <0.5 and >1.4 (p<0.001), 0.5-0.9 and >1.4 (p=0.04), 0.9-1.4 and >1.4 (p=0.05). Proportion of tibial calcium to overall PCS was much lower in ABI<0.5: 0.0003 vs ABI>1.4: 0.357 (p=0.02). Mean PCS may be a valid measure of PAD severity and percentage of tibial calcium may help quantify PAD burden in non-compressible vessels. Our study serves as proof of concept for a comprehensive PCS system to diagnose and evaluate PAD severity, particularly in high-risk subpopulations where non-invasive studies may be unreliable.