Impact of diabetes mellitus on coronary artery plaque characteristics and outcomes in the SCOT-HEART trial.

Background: Diabetes mellitus is an established cardiovascular risk factor. We assessed the impact of diabetes mellitus on quantitative plaque and long-term outcomes in patients with and without diabetes mellitus in the Scottish COmputed Tomography of the HEART (SCOT-HEART) trial.

Methods: Coronary artery calcium (CAC) was assessed on non-contrast computed tomography (CT). Coronary stenoses, visually assessed adverse plaque characteristics and quantitative plaque burdens (calcified, non-calcified, low attenuation and total, Autoplaque 2.5) were assessed on coronary CT angiography. Multivariable and survival analyses were performed.

Results: Images of 1769 patients were assessed (56 ​% male, 58 ​± ​9 years). Diabetes mellitus was present in 196 (11 ​%) patients. Patients with diabetes mellitus had higher 10-year cardiovascular risk score (29 [interquartile range 21, 40] versus 15 [9, 21] %, p ​< ​0.001) and CAC score (71 [1, 447] versus 17 [0, 209] Agatston units, p ​< ​0.001), but were not more likely to have obstructive disease or visually assessed adverse plaque characteristics. Patients with diabetes mellitus had higher quantitatively assessed calcified, non-calcified, low attenuation and total plaque burdens. After adjustment for age and sex, diabetes mellitus was an independent predictor of calcified plaque burden (p ​= ​0.009), but not the other plaque types. During 8.7 [IQR 8, 9.6] years follow-up, diabetes mellitus was associated with an increased risk of fatal or non-fatal myocardial infarction, adjusted for age and sex (hazard ratio 1.85, 95 ​% confidence interval 1.09 to 3.17, p ​= ​0.024).

Conclusion: Diabetes mellitus was an independent predictor of quantitatively assessed plaque burden, particularly calcified plaque, and was associated with an increased risk of myocardial infarction.