Incremental prognostic value of coronary computed tomographic angiography high-risk plaque characteristics in newly symptomatic patients

Background: The incremental prognostic value of the plaque features in coronary computed tomographic angiography (CTA) has not been well assessed. This study was designed to determine whether CTA high-risk plaques have prognostic value incremental to the Framingham risk score (FRS) and the severity of luminal obstruction. Methods: A total of 628 newly symptomatic patients without known coronary artery disease underwent CTA. They were followed for a median of 677 days during which there were 26 cardiac events, including cardiac death, acute myocardial infarction, and hospitalization for unstable angina. Incremental prognostic value of adding plaque characteristics to the number of diseased vessels and the FRS was evaluated using 3 Cox models and net reclassification indexes. Results: The discrimination index was significantly increased by adding the number of diseased vessels to the FRS (change in c-statistic from 65.8% to 78.6%, p = 0.028) but not significantly by further adding plaque characteristics (change in c-statistic from 78.6% to 80.0%, p = 0.812). However, improved model-fitting by adding plaque characteristics into the linear combination with risk score and the number of diseased vessels (p = 0.007 from likelihood ratio test) and the lowest value of Akaike's information criteria of that model indicated that plaque characteristics improved both predictive accuracy and discrimination perspective. More subjects reclassified by plaque characteristics were moved to directions consistent with their subsequent cardiac event status than in an inconsistent direction. Conclusions: Evaluation of CTA plaque characteristics may provide incremental prognostic value to the number of diseased vessels and the FRS.