Quantifying coronary atherosclerosis is central to risk stratification in suspected coronary artery disease (CAD). This study, published in the European Heart Journal Cardiovascular Imaging, evaluated the prognostic utility of segment involvement score (SIS) derived from coronary computed tomography angiography (CCTA) and compared its performance with coronary artery calcium score (CACS) in routine clinical practice. 

Patients undergoing CCTA for suspected CAD across 27 centers between 2006 and 2022 were included. SIS was defined as the number of coronary segments containing plaque, while CACS was calculated using the Agatston method. Outcomes included all-cause death, myocardial infarction (MI), and their composite, assessed over follow-up.

A total of 23,034 patients were followed for a median of 2.5 years. SIS distribution showed 61.4% with SIS=0, 12.6% with SIS=1, 8.2% with SIS=2, 5.7% with SIS=3, and 12.2% with SIS≥4. Compared with SIS=0, higher plaque burden (SIS≥4) was linked to increased adjusted risk of death (hazard ratio [HR] 1.39; 95% confidence interval [CI] 1.17-1.66), MI (HR 3.53; 95% CI 2.72-4.59), and the composite outcome (HR 1.88; 95% CI 1.62-2.18). 

Obstructive stenosis ≥50% was independently linked to outcomes but demonstrated lower discriminatory ability than SIS. Predictive performance of SIS and CACS was similar for composite outcomes and MI, while CACS showed better discrimination for all-cause death.

SIS and obstructive disease were associated with adverse outcomes. No additional prognostic advantage over CACS was observed in routine practice.