Abstract Introduction Cardiac rupture has been one of the most frequent fatal complications of acute myocardial infarction in cases series reported since 1977. However, in exceptional cases, the rupture of the left ventricle is contained by the pericardium and by fibrous tissue, forming a pseudoaneurysm, which is characterized by the absence of myocardial tissue in its wall and a relatively narrow neck between the ventricle and the ventricular chamber. Although there is no estimated time for rupture, it is well established that the risk of rupture is 30 to 40% and mortality up to 10%. Pseudoaneurysm is a rarer entity than rupture and is usually diagnosed incidentally by imaging methods in up to 48% of cases. The most frequent imaging method for their diagnosis is 2D echocardiography, followed by cardiac catheterization and finally cardiac magnetic resonance. The most frequent location of the pseudoaneurysm secondary to acute myocardial infarction is the inferior wall and the posterolateral wall of the left ventricle. Case Report We present 72-year-old male patient with a history of type 2 diabetes and smoking, who started symptoms with sudden onset of oppressive chest pain of 20 minutes duration, he did not attend medical attention. A month later, he went for a valuation with a first-contact physician, who referred him to our institution with a diagnosis of acute myocardial infarction without reperfusion therapy. At the initial assessment, it was found asymptomatic, in the resting ECG was found QS pattern with reversal of the T wave in leads DII, DIII and AVF. Cardiac SPECT was performed and showed an inferior transmural infarction, which extended as non-transmural to the inferolateral and inferoseptal walls, without ischemia. (Img. 1 and 2). A 2D and 3D transthoracic echocardiogram was performed, in which akinesia of the inferoseptal and apical walls was documented, as well as a saccular pseudoaneurysm of 5.6 X 4.7 cm in the basal and middle segment of the inferior and inferolateral walls, with an entrance orifice. 2.6 X 2.4 cm, as well as pericardial effusion. (Fig. 3 and 4). Coronary angiography was performed, demonstrating chronic total occlusion of the right coronary in its proximal segment and ostial obstruction of the left anterior descending. Cardiac magnetic resonance revealed inferior infarction and the presence of a pseudoaneurysm with lamellar thrombus was corroborated. (Img. 5). The patient was taken to surgical treatment, by reconstruction of the left ventricle with the Dor technique and CABG of the right coronary artery and the anterior descending artery. Receives medical treatment and a 1-month follow-up is in class I of the NYHA. Conclusion It is a clinical case about a potentially fatal complication of acute myocardial infarction, which in our case was detected incidentally since the patient had remained asymptomatic, there lies the importance of obtaining an accurate diagnosis in order to impact on the patient survival. Abstract P262 Figure. Pseudoaneurysm multi-modality images