HISTORY, CURRENT ILLNESS AND PHYSICAL EXAMINATION
60-year-old woman, whose personal history included: smoker, no other cardiovascular risk factors, severe hypoacusis, paroxysmal atrial fibrillation without anticoagulation by CHA2DS2-VASC 1 and obstructive sleep apnoea syndrome. She was being treated with bisoprolol and had no family history of interest.
The patient came to the emergency department for progressive dyspnoea on minimal effort for a week with orthopnoea and paroxysmal nocturnal dyspnoea.
She also had palpitations without chest pain. She had no other symptoms.

Physical examination showed BP 110/65 mmHg, 150 beats per minute, oxygen saturation of 90% at baseline, slight tachypnoea at rest without jugular ingurgitation, arrhythmic without audible murmurs on cardiac auscultation, crackles in both lung bases, with a normal abdomen on examination and malleolar oedema with fovea in the distal third of the lower limbs, with no signs of deep vein thrombosis. An electrocardiogram showed atrial fibrillation with rapid ventricular response (AF-RVR) and a chest X-ray showed signs of heart failure, and blood tests showed mild renal failure and mild anaemia. Beta-blocker treatment was started to control the heart rate and intravenous perfused furosemide was administered to achieve negative balance. An echocardiogram showed left ventricular dimensions at the upper limit of normality with a left ventricular ejection fraction (LVEF) of 50-55%.

COMPLEMENTARY TESTS
Laboratory tests on admission: leukocytes 10.8 mil/mcL, haemoglobin 11.4 g/dl, platelets 265 mil/mc, glycaemia 105 mg/dl, urea 69 mg/dl, creatinine 1.28 mg/dl, CPK 21 IU/L, sodium 133 mmol/L, potassium 4.6 mmol/L.
Electrocardiogram on admission: AF at 149 beats per minute, QRS axis at -9o, with narrow QRS, no other electrocardiographic abnormalities of note.
Chest X-ray: signs of pulmonary congestion, no pleural effusion with increased cardiothoracic index.
Echocardiogram: non-dilated left ventricle with mild hypertrophy and preserved LVEF without segmental alterations of contractility. Diastolic pattern with single E wave and lateral E/E" of 12. Mitral insufficiency grade II and slight atrial dilatation. Normofunctioning trivalve aortic valve. Non dilated right chambers with mild tricuspid insufficiency with estimated PSAP of 55 mmHg. Inferior vena cava 22 mm with reduced collapse and absence of pericardial effusion.
Echocardiogram in coronary unit: severely depressed LVEF with moderate dilatation of the left ventricle (82 ml/m2), mitral insufficiency grade III-IV, mild dilatation of the left atrium. Estimated PSAP of 65 mmHg.
Echocardiogram after coronary unit output: non-dilated left ventricle with normal LVEF without segmental alterations of contractility.
Mild mitral insufficiency without other notable alterations.

EVOLUTION
On the hospital ward, heart rate control was achieved with bisoprolol and a transthoracic echocardiogram was performed which showed normal left ventricular volumes with preserved LVEF and mild-moderate mitral insufficiency.
Three days after admission, the patient presented AF-RVR again with haemodynamic instability and respiratory failure secondary to pulmonary oedema, so she was transferred to the Coronary Unit and electrical cardioversion was performed, which was ineffective after several attempts at maximum energy. Digoxin was administered and haemodynamic support was instituted with noradrenaline, orotracheal intubation and invasive ventilation. A repeat echocardiogram showed dilatation and severe dysfunction of the left ventricle with moderate-severe functional mitral regurgitation. Progressively, after haemodynamic improvement, beta-blockers were introduced, achieving rate control and withdrawing haemodynamic and ventilatory support. Coronary angiography showed angiographically normal coronary arteries and she was transferred to the ward where the echocardiogram was repeated and showed recovery of LVEF and left ventricular dimensions. The patient was discharged with atrial fibrillation and controlled ventricular response and a diagnosis of tachycardiomyopathy under treatment with bisoprolol 5 mg every 12 hours and sintrom.

DIAGNOSIS
Tachycardiomyopathy secondary to atrial fibrillation with rapid ventricular response.
