Progression of Coronary Artery Calcium and Risk of First Myocardial Infarction in Patients Receiving Cholesterol-Lowering Therapy

Abstract

Objective— Statins reduce cardiovascular risk and slow progression of coronary artery calcium (CAC). We investigated whether CAC progression and low-density lipoprotein (LDL) reduction have a complementary prognostic impact. Methods and Results— We measured the change in CAC in 495 asymptomatic subjects submitted to sequential electron-beam tomography (EBT) scanning. Statins were started after the initial EBT scan. Myocardial infarction (MI) was recorded in 41 subjects during a follow-up of 3.2±0.7 years. Mean LDL level did not differ between groups (118±25 mg/dL versus 122±30 mg/dL, MI versus no MI). On average, MI subjects demonstrated a CAC change of 42%±23% yearly; event-free subjects showed a 17%±25% yearly change ( P =0.0001). Relative risk of having an MI in the presence of CAC progression was 17.2-fold (95% CI: 4.1 to 71.2) higher than without CAC progression ( P <0.0001). In a Cox proportional hazard model, the follow-up score ( P =0.034) as well as a score change >15% per year ( P <0.001) were independent predictors of time to MI. Conclusions— Progression of CAC was significantly greater in patients receiving statins who had an MI compared with event-free subjects despite similar LDL control. Continued expansion of CAC may indicate failure of some patients to benefit from statin therapy and an increased risk of having cardiovascular events.