The risk of developing clinical manifestations of ischemic heart disease is currently assessed by using integrated multifactorial prediction models based on the presence of non-modifiable risk factors, such as age, gender and a family history of early ischemic heart disease along with risk factors which are defined as conventional, such as arterial hypertension, hypercholesterolemia, cigarette smoking and diabetes mellitus.

However, if the relationship between risk factors and ischemic heart disease clinical manifestations shows some limitations, the relation between risk factors and the coronary atherosclerosis process underlying most ischemic syndromes seems to be even weaker.

In fact there is significant individual variability and the limits of such relationship are demonstrated by a non negligible number of subjects at the outliers of mean behaviour of the prediction model. At one outlier, in the presence of multiple risk factors, these subjects do not develop neither coronary events nor coronary atherosclerosis whereas, at the other, coronary events and disease occur in the absence of risk factors.This study aims at detecting new protection and susceptibility factors, thus enabling to formulate new etiopathogenetic hypotheses concerning coronary atherosclerosis and to identify new therapeutic targets.

Inclusion Criteria:

• Group A: subjects with total absence of coronary atherosclerosis and 3 or more risk factors (reported by the subject or documented at the MDCT)
• Group B: subjects with diffuse coronary atherosclerosis extended to more than 5 of the 16 segments according to the American Heart Association classification and 0-1 risk factor (reported by the subject or documented at the MDCT) with the exclusion of patients with type 1 or type 2 diabetes mellitus as single risk factor.

Using the same criteria, two control populations will be selected, with a case:control 1:1 ratio, consisting in:

• Group C: subjects with total absence of coronary atherosclerosis and 0-1 risk factor (reported by the subject or documented at the MDCT)
• Group D: subjects with diffuse coronary atherosclerosis extended to more than 5 of the 16 segments according to the American Heart Association classification and 3 or more risk factors (reported by the subject or documented at the MDCT) with the exclusion of patients with type 1 or type 2 diabetes mellitus as single risk factor.

Exclusion Criteria:

• common contraindications to MDCT (chronic renal failure with serum creatinine > 2.0 mg/dl, suspected pregnancy, arrhythmias, body mass index > 40, allergy to iodized contrast agent).
• previous cardiovascular events (heart failure, acute myocardial infarction, unstable angina, chronic stable angina, previous percutaneous or surgery coronary revascularization) both clinically evident and found by conventional diagnostic methods previous performed.
• subjects which MDCT does not meet the quality control criteria defined below in the protocol.
• patients with previous documented or identified at the moment of MDCT such as dilated cardiomyopathy regardless of etiology, obstructive hypertrophic cardiomyopathy, atrial fibrillation, myocarditis and inflammatory vascular disease.

Male and female subjects between 45 and 75 years old who, in the absence of any previous clinical manifestations of ischemic heart disease, will undergo coronary arteries study.