Noncoronary Measures Enhance the Predictive Value of Cardiac CT Above Traditional Risk Factors and CAC Score in the General Population

Abstract

Objectives: The aim of this study was to determine whether noncoronary measures from cardiac computed tomography (CT) may enhance the prognostic value of this imaging technology.

Background: When cardiac CT is performed for quantification of coronary artery calcium (CAC) score, information on other cardiac and thoracic structures is available.

Methods: Participants without known cardiovascular disease from the prospective population based Heinz Nixdorf Recall study underwent noncontrast cardiac CT for CAC score quantification. From CT, epicardial adipose tissue (EAT) volume, left ventricular and left atrial (LA) axial area index, ascending and descending aortic diameters, as well as aortic valve, mitral ring, and thoracic aortic calcification (TAC) were assessed. Incident cardiovascular events included myocardial infarction, stroke, and cardiovascular death. The prognostic value of CT-derived parameters was assessed by Cox regression analysis, receiver operating characteristics, and net reclassification improvement.

Results: From 3,630 subjects (59 ± 8 years of age, 46% male), 241 (6.6%) developed a cardiovascular event during 9.9 ± 2.6 years of follow-up. In multivariable Cox regression analysis including Framingham Risk Score, CAC (as log[CAC + 1]), and CT parameters, LA index (hazard ratio [HR]: 1.22 [95% confidence interval [CI]: 1.05 to 1.41] per SD; p = 0.010) and EAT volume (HR: 1.15 [95% CI: 1.01 to 1.30] per SD; p = 0.031) were significantly associated with incident events. In addition, presence of TAC showed an elevated event rate (HR: 1.33 [95% CI: 0.97 to 1.81]; p = 0.08), whereas all other CT-derived parameters showed no relevant association. The LA index, EAT volume, and presence of TAC together improved the prediction of events over Framingham Risk Score and CAC in receiver operating characteristics analysis (area under the curve: 0.749 to 0.764; p = 0.011), and let to a significant net reclassification improvement (HR: 38.0%; 95% CI: 25.1% to 50.8%).

Conclusion: Assessment of LA index, EAT volume, and TAC from non-contrast-enhanced cardiac CT improves the prediction of incident hard cardiovascular events above CAC and established risk factors, indicating that quantification of these noncoronary measures may improve the prognostic value of this imaging technology.

Keywords: Heinz Nixdorf Recall Study; cardiac CT; epicardial adipose tissue; left atrial size; thoracic aortic calcification.