Coronary calcium in patients with and without diabetes: first manifestation of acute or chronic coronary events is characterized by different calcification patterns

Background: Coronary artery calcification (CAC) is closely related to coronary atherosclerosis. However, less is known about the clinical significance of extensive CAC (ECAC) in regard to types of first coronary events (acute vs. chronic). Diabetes mellitus (DM) represents a strong risk factor for CAD although its association with CAC is controversial. Aiming to elucidate these controversies we investigated the long-term outcome of coronary artery disease (CAD) in relation to degree of CAC in patients with and without DM from our annual cheek-up outpatient clinic. Methods: Coronary artery computed tomography (CT) was performed in 667 patients who were yearly evaluated during a mean follow-up period of 6.3 +/- 3.4 year. The following 4 CAC categories were established: calcium absence; total calcium score (TCS): 1-100 AU; TCS: 101-600 AU and ECAC: TCS above 600 AU. Acute event was defined as first acute myocardial infarction (MI) or a new unstable angina. First chronic event was defined as a positive stress test with a consequent elective percutaneous coronary intervention or coronary artery bypass grafting. Results: 628 subjects (94%) were free from any cardiac events, 39 (6%) experienced first cardiac event: 18 of them suffered acute and 21 chronic events. There were 67 patients with and 600 patients without DM: 78% of patients with DM presented CAC vs. 50% of patients without DM (p < 0.001). The mean TCS was 17 times higher in the chronic than in the acute events group: 914 vs. 55 AU, p < 0.001. In 95% of the patients with chronic events more than one calcified vessel was found, compared to 67% of the patients with acute events and only 30% of those without events (p < 0.001). Incidence of CAD events (all types pooled together) rose consequently from 2% in subjects without CAC to 34% in subjects with ECAC (p < 0.001). However, among the 32 subjects with ECAC, 11 (34%) developed chronic event while none of them had acute event. In contrast, none of subjects with TCS =0 or TCS 1-100 AU presented with chronic events. Subjects with TCS 101-600 AU presented 10 (9%) chronic and 5 (4.5%) acute events (p < 0.001). Conclusions: Asymptomatic subjects with ECAC are not firstly manifested as acute coronary events but presented a high level of chronic CAD-related events during the 6.3 +/- 3.4 year follow-up. In contrast, first acute CAD-related events occurred mostly in subjects with mild and moderate CAC score.