Prognostic implications of non-culprit plaques in acute coronary syndrome: non-invasive assessment with coronary CT angiography

Purpose: Coronary CTA is a reliable non-invasive risk stratification tool for patients with coronary artery disease. However, little is known about the prognostic implications of non-culprit plaques seen on coronary CTA in patients with ACS. In tis study, we sought ou to determine the prognostic value of non-culprit plaques on coronary CT angiography (CTA) in patients with acute coronary syndrome. Methods: Coronary CTA was performed in 169 ACS patients (mean 59±11 years, 129 males) during index admission. Overall residual coronary artery plaque burden was determined using a segment stenosis score for each patient: 0-20% stenosis: score 0, 20-50%: score 1, 50-70%: score 2, >70%: score 3, (maximal score of 48 per patient). Follow-up was performed for the occurrence of major adverse cardiac events (MACE) not related to the initially culprit lesion; cardiac death, recurrent non-fatal myocardial infarction or coronary revascularization after 90 days. Results: Follow-up was completed in 152 (90%) patients with a median follow-up time of 4.8 (IQR 2.6-6.6) years. MACE occurred in 36 (24%) patients, consisting of 6 cardiac deaths, 11 non-fatal myocardial infarctions and 19 coronary revascularisations. A total of 2432 segments were evaluated and 404 were considered non-diagnostic while 172 were censored because of treatment. The median segment stenosis score was higher in patients with MACE (12 [6-16] vs. 7 [3-11], p = 0.005). Non-culprit plaques with a >50% stenose were more often seen in patients with MACE than in those without (83% vs. 52%, p = 0.001). Dyslipidemia (hazard ratio [HR] 3.1 [95% CI 1.4 - 6.6], diabetes mellitus (HR 4.8 [2.3 - 10.3]) and TIMI risk score (HR 1.5 [1.2 - 1.9]) were univariable predictors of MACE, as well as the segment stenosis score (HR 1.09 [1.03 – 1.15]) and >50% stenosis of a non-culprit plaque (HR 3.7 [1.5 - 8.8]). After adjusting for clinical characteristics, >50% stenosis of a non-culprit plaque (HR 3.69 [1.41-9.68]) remained an independent predictor of MACE. Conclusions: Almost a quarter of ACS patients experienced a non-culprit related MACE during 5 years follow-up in this study. Coronary CTA detects non-culprit plaques in ACS patients and identifies those at risk of future non-culprit cardiac events with incremental value over clinical variables.