Insulin resistance and acute coronary syndrome

BACKGROUND: Insulin resistance (IR), which can be quantified by HOMA index (fasting glucose X fasting insulin/22.5), is considered the "primum movens" for the development of Metabolic Syndrome. Many authors have suggested that insulin resistance could raise both incidence and mortality of coronary heart disease (CHD). IR is also associated with important predictors of cardiovascular disease, as increased concentration of LDL or triglyceride, decreased concentration of HDL, high systolic blood pressure, visceral obesity. There is accumulating evidence that chronic sub-clinical inflammation, as measured by inflammatory markers as C-reactive protein (CRP) and fibrinogen, is related with insulin resistance. AIM OF THE STUDY: To clarify if insulin resistance would predict cardiovascular disease independently of the other risk factors, such as hypertension, visceral obesity or dyslipidemia, by focusing our attention on the relation between Acute Coronary Syndrome (ACS) and high HOMA index. METHODS: We evaluated glucose and insulin levels at baseline and post-prandial phase, in order to estimate HOMA index in both the conditions; we related the data obtained with the incidence of cardiovascular events, also investigating traditional cardiovascular risk factors. The cohort included 118 patients with a clinical diagnosis of ACS and excluded those with type 1 diabetes, acute inflammatory diseases, hepatic or renal failure, disreactive disorders, autoimmunity and cancer. SUBJECTS: Subjects were followed-up for a period of 1 year, being subdivided in three groups: (1) subjects at elevated HOMA (HOMA > or = 6); (2) subjects at intermediate HOMA (HOMA <6 and > or = 2); (3) subjects at low HOMA (HOMA < or = 2). We considered as end points new cardiovascular events, cerebrovascular events (both TIA and stroke), procedures of revascularization with angioplasty or surgery, cardiovascular death, sudden death. RESULTS: Patients with elevated HOMA have a higher incidence of previous cardio- and cerebrovascular events (p=0.03), myocardial infarction without ST elevation (p=0.005), unstable angina (p=0.01), asymptomatic carotid plaques (p=0.05), depressed systolic function (p=0.05); we found, also, a significant statistic correlation between HOMA index and high levels of CRP, fibrinogen, serum creatinine and TnI. Cardiovascular and cerebrovascular events were registered in 61% of patients with elevated HOMA during the follow up, despite of 25% registered in the control group: so we could consider HOMA index as a negative prognostic variable, also in virtue by the statistic correlation with the inflammatory markers, whose power of prediction is already known. CONCLUSIONS: Beyond traditional cardiovascular risk factors, insulin resistance quantified by HOMA index seems to significantly have an important prognostic role, both in primary and secondary prevention in patients with Acute Coronary Syndrome.