Coronary computed tomography angiography (CTA)-guided vulnerable plaque characteristics have predictive value for future acute coronary syndrome (ACS) in high-risk patients according to Incident COronary EveNts Identified by Computed Tomography (ICONIC) trial which is published in the Journal of the American College of Cardiology.
Acute myocardial infarctions resulting from unstable plaque in patients with coronary artery disease (CAD) causes a substantial portion of cardiovascular morbidity and mortality. Despite the results of intravascular ultrasound (IVUS) studies, demonstrate that precursors of culprit lesions are commonly nonobstructive, current clinical practice has focused on lesion severity in order to predict future plaque rupture. However, the prognostic influence of plaque composition on future ACS is not completely understood.
To explore the prognostic significance of plaque features for predicting acute coronary syndrome by CTA, Dr. Hyuk-jae Chang along with his team conducted a multicentered case-control study in 13 countries screened around 25,251 people. They included subjects with no prior history of CAD and ACS. The final ICONIC study cohort comprised 234 ACS cases and 234 propensity-matched control subjects with baseline coronary CTA. Subjects experiencing ACS were matched 1:1 to control those without ACS and prior CAD. All of the patients in both groups underwent a baseline coronary CTA and were followed up for 3.4 years for all cause mortality and major adverse cardiac events.
Baseline CTA analysis included quantitative measurement of lesion length, volume and mean plaque burden. Plaque characteristics were defined as necrotic core, fibrofatty, fibrous, and calcified according to pre-defined Hounsfield unit thresholds. High-risk plaque (HRP) was defined as the presence within a coronary lesion of ≥2 features including positive remodeling, low attenuation plaque, and spotty calcification. Cutpoints of ≥ 50% and ≥ 70% were used for obstructive CAD.
Patients with ACS did not significantly differ from control subjects in terms of calcified, fibrous, or total plaque volume, but had significantly higher fibrofatty (p = 0.009) and necrotic core volumes ( p = 0.026). High risk plaque was found more frequently in patients with ACS than control subjects (52.1% vs. 33.3%; p = 0.003). Moreover, the presence of HRP was significantly associated with ACS (HR: 1.593 (95% CI); p = 0.001). Additionally,the highest percentage of diameter stenosis severity was an indicator of future adverse events (HR: 1.010 (95% CI); p = 0.002).
Interestingly, only 34.8% of ACS patients had an obstructive coronary lesion with ≥50% diameter stenosis and 12.8% of them had ≥70% stenosis prior to ACS. With respect to the lesion level, precursor lesions of culprit plaques were identified as causing more than 50% and 70% luminal obstruction only 24.8% and 4.7%, respectively.
The authors emphasized that the highest percentage of diameter severity, fibro-fatty and necrotic core plaques are significant predictors for future ACS events in a stable CAD patient. Furthermore, the lesion with greatest overall plaque volume as well as fibrofatty and necrotic volume has the greatest probability of becoming a culprit lesion.
The findings of this study showcase the idea that the decision making for treatment should also be guided by plaque characteristics in addition to the measures of stenosis.