Coronary angioplasty is rather frequently performed in such situations, presumably because, changes in the atherosclerotic plaque under drug treatment, have remained poorly described so far. Intravascular ultrasound (IVUS) enables a precise description of coronary atheroma, better than the one provided by coronary angiography.

According to current guidelines, patients with coronary lesions with stenosis <70% should receive optimal secondary prevention drug treatment without angioplasty, even after an acute coronary syndrome (ACS). Nevertheless, coronary angioplasty is rather frequently performed in such situations, presumably because, changes in the atherosclerotic plaque under drug treatment, have remained poorly described so far. Intravascular ultrasound (IVUS) enables a precise description of coronary atheroma, better than the one provided by coronary angiography.

The first objective is to assess by endo-coronary ultrasound, under optimal medical treatment, the evolution of atheromatous plaque (with stenosis <70%). The evolution will be appreciated after 12 months of treatment the percentage of atheromatous volume (PVA). The aim of the first secondary objective to evaluate, after 12 months of treatment, the evolution of the total atheromatous volume (VAT) and the standardized total atheromatous volume (standardized VAT). The Second secondary objective is to evaluate by endo-coronary ultrasound, the evolution of a stable atheromatous plaque. This analysis will be performed in patients with a second coronary lesion (atheroma plaque), resulting in less than 70% stenosis, and not being responsible for acute coronary syndrome. The evolution of the stable plate will be compared to the evolution of the unstable plate. Finally, the third secondary objective is to estimate the incidence of clinical events (death, acute coronary syndromes, ischemic stroke, revascularization, hospitalization for heart failure) within 12 months of the occurrence of an acute coronary syndrome managed by medical treatment optimal secondary prevention (without performing angioplasty).

Inclusion Criteria:

• adult patients hospitalized for ACS, for whom the target lesion has less than 70% stenosis and not treated with coronary angioplasty.

Exclusion Criteria:

• Patients presenting with a target lesion with ≥70% stenosis ; Patients for whom the target lesion is treated with coronary angioplasty ; Interventions: A first IVUS will be performed after the acute coronary event (baseline) and will be done again one-year after to assess changes in the atherosclerotic plaques.

female and male aged more than 18 years hospitalized for acute coronary syndrom