Prognostic value of CT coronary angiography in diabetic and non-diabetic subjects with suspected CAD: importance of presenting symptoms

AIM To assess the prognostic relevance of 64-slice computed tomography coronary angiography (CT-CA) and symptoms in diabetics and non-diabetics referred for cardiac evaluation. METHODS We followed 210 patients with diabetes type 2 (DM) and 203 non-diabetic patients referred for CT-CA for ruling out coronary artery disease (CAD). Patients were without known history of CAD and were divided into four categories on the basis of symptoms at presentation (none, atypical angina, typical angina and dyspnoea). Clinical end points were major cardiac events (MACE): cardiac-related death, non-fatal myocardial infarction, unstable angina and cardiac revascularizations. Cox proportional hazard models, with and without adjustment for risk factors and multiplicative interaction term (obstructive CAD × DM), were developed to predict outcome. RESULTS DM patients with dyspnoea or who were asymptomatic showed a higher prevalence of obstructive CAD than non-diabetics (p ≤ 0.01). At mean follow-up of 20.4 months, DM patients had worse cardiac event-free survival in comparison with non-DM patients (90% vs. 81%, p = 0.02). In multivariate analysis, CT-CA evidence of obstructive CAD (in DM patients: HR: 6.4; 95% CI: 2.3-17.5; p < 0.001; in non-DM patients: HR: 7.4; 95% CI: 2.1-26.7; p = 0.002) and the presence of typical angina (in DM patients: HR: 2.9; 95% CI: 1.3-6.3; p = 0.007; in non-DM patients: HR: 2.7; 95% CI: 1.1-7.1; p = 0.03) were independent predictors of MACE in both groups. Furthermore, other independent outcome predictors included dyspnoea (HR: 3.8; 95% CI: 1.7-8.5; p = 0.001), the number of segments with any CAD (HR: 1.1; 95% CI: 1.001-1.2; p = 0.04) in DM patients and coronary calcium score >100 in non-DM patients (HR: 5.6; 95% CI: 1.4-21.5; p = 0.01). In Cox regression analysis of the overall population, interaction term obstructive CAD × DM resulted in non-significance. CONCLUSIONS Among DM patients, dyspnoea carried a high event risk with a MACE rate four times higher. CT-CA findings were strongly predictive of outcome and proved valuable for further risk stratification.