ACUTE CORONARY SYNDROME IN PATIENTS WITH NORMAL LDL-C LEVELS: CLINICAL FEATURES AND POSSIBLE MECHANISMS

Abstract

Acute coronary syndrome (ACS) is one of the major manifestations of coronary artery disease and remains an important cause of morbidity and mortality worldwide. Low-density lipoprotein cholesterol (LDL-C) is a well-established risk factor for atherosclerosis and an important target of cardiovascular prevention. However, ACS can also occur in patients whose LDL-C concentration is not markedly elevated. This observation suggests that the development of ACS cannot always be explained by the current LDL-C level alone. The aim of this review is to summarize possible mechanisms of ACS in patients with apparently normal LDL-C and to describe the clinical factors that may contribute to cardiovascular risk in these patients. Particular attention is given to endothelial dysfunction, inflammation, plaque instability, lipoprotein(a), apolipoprotein B, triglyceride-rich lipoproteins, diabetes mellitus, hypertension, and smoking. Current evidence indicates that a normal LDL-C value does not necessarily mean a low lifetime exposure to atherogenic lipoproteins or the absence of coronary atherosclerosis. Additional lipid and clinical parameters may therefore be useful for a more complete assessment of cardiovascular risk. Understanding these mechanisms is important for the clinical evaluation and secondary prevention of patients with ACS.