HISTORY, CURRENT ILLNESS AND PHYSICAL EXAMINATION
46-year-old female, civil servant, with no illnesses of interest or regular medication. Never smoked. No cardiovascular risk factors or consumption of alcohol or other toxic substances. No family history of heart disease or sudden death. Intervened tonsillectomy in infancy, caesarean section and hysterectomy.
Cardiovascular asymptomatic until the previous 2 weeks, who begins with moderate exertional dyspnoea that prevents her from carrying out her normal life, together with orthopnoea, oliguria and the appearance of progressive oedema in the lower limbs. At all times he denies chest pain, palpitations, dizziness or syncope. Neither did he present febrile syndrome or infectious symptoms.
Physical examination revealed a blood pressure of 130/60 mmHg, a heart rate of 90 bpm, afebrile and eupneic with nasal spectacles at 2 bpm. On auscultation, she had a bibasal crackles and a diastolic murmur II/IV at mitral level with an occasional "plop". Abdomen with no findings and lower extremities with oedema with distal fovea, with no evidence of venous thrombosis.

COMPLEMENTARY TESTS
Electrocardiogram (ECG): sinus rhythm at 90 bpm, normal PR (152 ms) with bimodal P in relation to left atrial enlargement. Narrow QRS with normal axis without repolarisation alterations.
Chest X-ray: normal cardiothoracic index with discrete vascular redistribution.



Analyses:
Biochemistry: glucose 98 mg/dl (70-110), urea 16 mg/dl [10-50], creatinine 0.78 mg/dl (0.7-1.2), glomerular filtration rate > 60 ml/min (MDRD-4) (> 60), Na 144 mmol/l (135-145), K 3.9 mmol/l [3.5-5.1]. ProBNP 2110 pg/ml (10-125). Normal liver function tests.
Thyroid hormones normal.
CBC: leukocytes 9,400/cc (normal formula) (4,500-11,400), Hb 14.8 g/dl (13.2-16.8), platelets 211,000 (157,000-334,000).
Coagulation: INR 1.13 (0.8-1.3), PT 82% (70-120), aPTT 24.4s (24.8-40.3).

PET CT scan protocol: no repletion defects in the pulmonary trunk or main or segmental branches suggestive of thromboembolism were observed. A well-defined hypodense mass measuring 5 x 4 cm located at the level of the left atrium, which crosses the valve towards the left ventricle, is striking, ruling out myxoma or large thrombus. It is accompanied by bilateral pleural effusions and a linear interstitial pattern, with thickening of interlobular septa compatible with heart failure.

Transthoracic echocardiogram: left ventricle (LV) of normal size and thickness, with preserved LVEF (>60%) and no segmental contractility abnormalities.
Right ventricle (RV) of normal size and function (TAPSE 20 mm). Moderate left atrial dilatation with a large round heterogeneous mass measuring 5 x 3 cm, adhered to the interatrial septum which in diastole is introduced through the mitral annulus producing a moderate-severe stenosis (maximum gradient of 24 mmHg and mean of 14 mmHg, estimated area of 1.4 cm2), without insufficiency. Aortic and tricuspid valve without significant dysfunction.

Transesophageal echocardiogram: rounded intra-atrial mass measuring 5 x 3.5 cm, heterogeneous, with a wide pedicle measuring 2.7 x 1 cm that adheres to the inferior interatrial septum below the fossa ovalis, which it respects, which in diastole is introduced into the mitral annulus producing a significant stenosis (effective area of 1.4 cm2), with a mitral valve with thin leaflets without alterations. This mass is compatible with an atrial myxoma. The atrial appendage is free of thrombus.
Haemodynamic study: coronary arteries without significant stenosis.


CLINICAL EVOLUTION
The patient attended the emergency department where, given the presence of dyspnoea in a patient with no known heart disease, it was decided to perform a CAT scan with PET protocol, which ruled out the presence of pulmonary thromboembolism but revealed a striking mass in the left atrium, for which reason cardiology was consulted and admitted to his care as the debut of heart failure.
Based on the CT scan findings and pathological auscultation, with a clear clinical suspicion, a transthoracic and transesophageal echocardiogram was performed which showed the presence of a giant pedunculated mass in the left atrium compatible with a myxoma which, in diastole, protruded into the left ventricle causing significant mitral stenosis. The case was presented to cardiac surgery and it was decided to remove the mass. Intraoperatively, a tumour with a base of implantation inferior to the fossa ovalis in continuity with the posterior mitral annulus was observed and complete excision was performed, including part of the interatrial septum, with subsequent closure of the defect with a patch of autologous pericardium. The mitral valve is morphologically normal, with thin leaflets, and intraoperative transesophageal echocardiography shows normal function after removal of the mass.

She was extubated a few hours later without incident and, after a few days, was discharged. The results of the pathological anatomy confirmed the presence of atrial myxoma, with no evidence of malignancy. She is currently being monitored on an outpatient basis by the cardiology department. A follow-up echocardiogram was performed one year later, which showed no abnormalities, with no recurrence of the myxoma, and since then she has been stable and asymptomatic.

DIAGNOSIS
Congestive heart failure. First episode.
Giant atrial myxoma.
Moderate-severe dynamic mitral stenosis.
Excision of the mass and repair of the septum with pericardial patch.
