HISTORY, CURRENT ILLNESS AND PHYSICAL EXAMINATION
60-year-old woman allergic to ASA. Ex-smoker. The only history is that she underwent hysterectomy and double adnexectomy in 2008. No cardiological history. She presented with progressive dyspnoea of one month's duration, associated with presyncopal symptoms. On the day of admission the patient suffered a syncopal episode. She was attended at home and was found to have atrial fibrillation with rapid ventricular response and acute pulmonary oedema. She was admitted to the ICU.

On arrival at the ICU physical examination was performed: BP 105/57 mmHg, HR 160 bpm, T 36.4 oC, SatO2 89 % with Ventimask at 10 litres. Patient conscious and oriented. Tachypnoea. No jugular ingurgitation or hepatojugular reflux. Cardiac auscultation: arrhythmic heart sounds at high frequency, interrupted by breath sounds. Pulmonary auscultation: bilateral crackles up to upper fields. Abdomen soft, depressible, not painful on palpation, no masses or megaliths palpable. Peristalsis preserved. No oedema in the lower extremities or signs of DVT.

COMPLEMENTARY TESTS
ECG on arrival at ICU: atrial fibrillation 160 bpm. Chest X-ray: bilateral interstitial infiltrate and bilateral pleural effusion, compatible with acute pulmonary oedema. Blood tests on arrival in the ICU: arterial blood gases pH 7.48, pCO2 39.4, HCO3 28.8, Sat O2 90.5%, pO2 62 mmHg. Biochemistry: creatinine 0.75 mg/dl. Urea 112 mg/dl. Calcium 7.7 mg/dl. Mg 2.3 mg/dl. Total protein 5.1 g/dl. Cl 112 mEq/l. Na 148 mEq/L. K 4.6 mEq/L. Haemogram: 15,000 leucocytes/uL with 88.3 % neutrophils and 6.1 % lymphocytes. Haemoglobin 9.6 g/dl. Hto 31.2 %. Platelets 211,000/uL. Coagulation: INR 1,36. Prothrombin activity 68 %, TTP 60 s, PT 15.20 s. Transthoracic and transesophageal echocardiogram: LV neither dilated nor hypertrophic. Preserved LVEF (estimated by Simspon 60 %). Left atrium slightly dilated (area 22 cm2). Left atrial appendage free of thrombus. RV of normal size and systolic function (TAPSE 23 mm, S wave by lateral TDI 10.5 cm/s). A large mass (7 x 3 cm) with slightly irregular borders and homogeneous density was observed in the left atrium. It is attached to the interatrial septum, prolapsing in diastole through the mitral valve and generating moderate restriction to its opening (mean transmitral gradient 7.5 mmHg). Mild MI. Given the echocardiographic characteristics, it appears to be a cardiac myxoma, without being able to rule out malignancy. Atrial septum of normal echocardiographic characteristics without flow through it. Aortic valve: trivalve with normal kinetics, no restriction to its opening, no reflux. Tricuspid valve: Mild TR. RV-AD gradient of 29 mmHg. IVC and suprahepatic valves not dilated, no flow reversal and inspiratory non-collapse. Estimated PAPs of 33 mmHg. Absence of pericardial effusion. Aortic root, ascending and descending thoracic aorta of normal size and echoic characteristics. Cardio-MRI: study by means of TI, T2, STIR sequences in axial, 2C, 3C, 4C and by means of iv contrast (angio-MRI) and late enhancement sequence in 2C and 4C. Voluminous mobile tumour in the left atrial cavity measuring 7 x 4.5 cm extending to the posteroinferior region of the left atrium. It presents a pedicle with a base of implantation in the interatrial septum of approximately 2 cm, in the middle third of the septum (proximity of the fossa ovalis) with slightly mameloned contours, with part of the mass prolapsing through the mitral valve in early diastole. It presents intermediate intensity in T1 that increases in T2. After contrast administration, it appears irregularly perfused, as well as with heterogeneous uptake in late gadolinium enhancement sequence. Given the presentation and behaviour in the different sequences, the mass is compatible with a sarcomatous strain. Cardiac catheterisation: coronary arteries without angiographic lesions.

EVOLUTION
After performing complementary tests and given the clinical situation of the patient, urgent surgery was decided. Under extracorporeal circulation (ECC), a voluminous tumour infiltrating the atrioventricular groove and the interatrial septum was resected, with the appearance of malignancy. Mitral valve replacement with a metallic prosthesis and closure of the septal defect with pericardium were performed. During the first 72-96 postoperative hours, the patient remained under deep sedoanalgesia due to severe refractory hypotension, in the context of post-ACS inflammatory response syndrome (SIRS); requiring vigorous volume expansion, as well as high doses of noradrenaline (NA) and vasopressin in continuous perfusion, associating continuous renal replacement therapy (CRRT) at maximum doses of ultrafiltration due to incipient acute renal failure (ARF). Once the vasoplegia had resolved, sedation could be withdrawn and weaning from mechanical ventilation could be initiated. The patient could be extubated with normal level of consciousness, initially maintaining good respiratory mechanics with O2 Sat > 95% with oxygen therapy at medium flows. However, respiratory mechanics progressively worsened. A TTE was performed which ruled out cardiological complications with a normally functioning prosthesis; and a chest X-ray showed bilateral interstitial infiltrate compatible with ARDS, requiring reintubation. The evolution was torpid, with exitus 7 days after the cardiac postoperative period. Finally, the anatomopathological diagnosis was high-grade pleomorphic sarcoma.

DIAGNOSIS
High-grade cardiac pleomorphic sarcoma in the left atrium.
Acute heart failure due to obstruction to left ventricular filling. Urgent surgery for tumour resection and mechanical mitral prosthesis.
Poor postoperative evolution with systemic inflammatory response syndrome and exitus.
