Abstract Introduction Infective Endocarditis is a complex entity with great variability of clinical manifestations and a broad spectrum of complications. The prognosis depends not only on the baseline characteristics of the patient, but also on the agent and the complications, both local and systemic, with clinical repercussion. Two clinical cases are presented. A 67-year-old woman with history of uncharacterized aortic valve disease, presented in the emergency department with a 3-month evolution of asthenia and anorexia, and ocasional fever. She presented pallor, with a systolic murmur II/VI audible throughout the precordium and no other abnormalities in physical examination. Blood tests showed Hb 9g/dL with normal MCV and MCH, no leucocytosis, CRP 132mg/L, mild elevation of troponin I (0.32ng/ml; N <0.04ng / ml) and erythrocyturia. Transthoracic and transesophageal echocardiograms (TTE and TEE) showed a mass on the aortic valve suggestive of vegetation, conditioning a moderate aortic regurgitation (AoR) and mitroaortic pseudoaneurysm. Another 49-year-old female patient, submitted during childhood to a subaortic aneurysm, intraventricular comunication, AoR and aortic coarctation repair, presented with deterioration of functional and neurological status, associated with fever and lower limb edema. At examination she had tachypnea, tachycardia, pallor, aortic systolic murmur and signs of pulmonary congestion. Blood tests had leukocytosis and neutrophilia, CRP 174mg/L, Hb 9.6g/dL, elevation of liver enzymes, spontaneous INR 1.4 and no renal damage. TTE and TEE showed a mobile vegetation attached to the ventricular face of the aortic valve with major AoR and perivalvular abscess fistulized to the left ventricle. Both patients were treated with empirical therapy with gentamicin, ampicillin, and flucloxacillin. The first case evolved with hemodynamic stability, without heart failure or distant embolization. It was isolated a multisensitive Strept. gordonii and antibiotic therapy was de-escalated to ampicillin alone. In the second case, the patient showed rapidly progressive clinical deterioration with hypoxemic respiratory failure and cardiogenic shock requiring vasopressor support, and was urgently presented to a surgical center. No microorganism was isolated and broad-spectrum antibiotic therapy was maintained. She eventually died before she underwent valve surgery. On the other hand, in the first case, 6 weeks of antibiotic therapy were completed and aortic valve replacement surgery was performed without complications. She was discharged without cardiovascular symptoms and has an unremarkable follow-up of 6 months. With these cases it was possible to demonstrate the variability of presentations and prognosis of the same entity, even if ab initio with equally severe local complications. The initial stratification of the prognosis, the initiation of early treatment and the adequacy of the surgical time for intervention are of importance. Abstract P1301 Figure. Imaging study of endocarditis