The utility of abdominal aortic calcification (AAC) for prediction of cardiovascular events (CVEs) in patients with acute coronary syndrome (ACS) remains to be determined. The aim of this prospective study was to determine the predictive value of the abdominal aortic calcification index (ACI), a semi-quantitative measure of AAC, for CVEs in patients with ACS. We evaluated 314 patients with ACS. All patients underwent successful percutaneous coronary intervention to the culprit coronary vessel without in-hospital adverse events. ACI was calculated on non-contrast computed tomography images. CVEs were defined as a composite of cardiovascular death, ACS recurrence, and stroke. During a median follow-up period of 19.1 months, CVEs occurred in 29 patients (9.2%). Multivariable regression analysis after adjustment for age and gender showed a significantly higher baseline ACI in patients with CVEs than in those without [median (interquartile ranges), 42.1 (25.9-60.2) vs. 20.8 (8.8-38.6) %; P = 0.021]. The cutoff value of ACI for prediction of CVEs, estimated by receiver-operating characteristic analysis, was 29.2%, with sensitivity of 76% and specificity of 64% (area under the curve, 0.69). After adjustment for conventional cardiovascular risk factors, Cox analysis showed high ACI (≥29.2%) to be significantly associated with increased risk of CVEs (P = 0.011; hazard ratio, 1.82). Multivariate analysis identified high ACI as an independent predictor of CVEs (P = 0.012; hazard ratio, 1.80). Stepwise forward selection procedure also showed that high ACI was a significant independent determinant of CVEs (P = 0.004; R2, 0.089). Both net reclassification improvement (0.64; P = 0.001) and integrated discrimination improvement (0.04; P < 0.001) improved significantly after the addition of high ACI to conventional risk factors. Evaluation of ACI using CT seems to provide valuable clinical information for proper assessment of mid-term CVEs in patients with ACS after percutaneous coronary intervention.
Keywords: Abdominal aortic calcification index; Acute coronary syndrome; Cardiovascular event; Non-contrast CT scan.