Introduction: Tachycardia-induced cardiomyopathy, a reversible cause of heart failure, is characterized by ventricular systolic dysfunction that is reversible with normalization of heart rate, without any other known etiology of heart failure.
Case presentation: We present the case of a 67-year-old male, active smoker, without history of any known cardiovascular disease, evaluated for symptoms of congestive heart failure NYHA II-III, apeared two months before. On physical examination, he presented tremor affecting both upper extremities, irregular heart rate (HR) of 140 bpm, blood pressure 120/70mm Hg, bilateral leg edema. Laboratory tests showed hyperthyroidism. Electrocardiogram revealed atrial fibrillation with rapid HR and the initial echocardiography – non-dilated left ventricle (LV) with mild diffuse hypokinesia, preserved LV ejection fraction and left atrium dilation. Considering hyperthyroidism being the cause of atrial fibrillation, the patient is treated with beta-blockers, oral anticoagulant therapy and antithyroid medication. After the correction of thyroid dysfunction, the atrial fibrillation with rapid HR persists, even with beta-blockers used at highest recommended dose. Echocardiography revealed LV dilation with progressive global LV systolic dysfunction and LV ejection fraction of 33%, diffuse hypokinesia, more importantly at the level of interventricular septum, elevated LV filling pressure, right chambers dilation, right sided pleural effusion and small pericardial effusion. The value of NTproBNP was 7600pg/mL. Interventricular septal hypokinesis and persistence of elevated HR after the normalization of thyroid function, lead to suspicion of myocardial ischaemia. Angiography showed normal epicardial coronary arteries. Electrical cardioversion restored sinus rhythm and antiarrhythmic drugs (propafenone) were used to maintain it. After one month, the follow-up echocardiogram revealed normalized cardiac chamber size and of left ventricular systolic function (LVEF 56%, NTproBNP 126 pg/mL). Particularity of the case: Atrial fibrillation with rapid HR occurring in the context of hyperthyroidism precipitated heart failure which maintains the arrhyth-mia despite correction of thyroid dysfunction, sugges-ting a vicious circle: atrial fibrillation induces the car-diomyopathy and the cardiomyopathy maintains atrial fibrillation.