Brady-tachycardia syndrome in a patient with thyroid dysfunction and Ebstein's anomaly An unusual partnership or a deadly triad.

Abstract

Introduction: Ebstein's anomaly (EA) is a congenital disease characterized by apical displacement of the tricuspid valve, which leads to tricuspid regurgitation and, over time, to right ventricular dilation and deterioration of systolic function. It is often associated with atrial septal defect and arrhythmias mediated by accessory pathways. Alterations in thyroid hormone levels can cause systemic complications, including heart involvement. Hypothyroidism, in particular, can lead to sinus bradycardia and myxomatous changes of the leaflets.

Clinical Case: A 55-year-old woman with no relevant medical history experienced syncope on three occasions over the past 3 months and a recent syncopal episode, along with feelings of anxiety and palpitations in the last 24 hours. Monitoring and ECG showed sinus bradycardia with bursts of isolated supraventricular and ventricular extrasystoles, as well as episodes of atrial tachycardia. Echocardiogram revealed a left ventricular ejection fraction (LVEF) of 46%, apical implantation of the septal leaflet of the tricuspid valve measuring 12.3 mm, and mild dilation of the right ventricle. These findings suggest a grade A Ebstein's anomaly according to Carpentier's classification. The Holter monitor confirmed the presence of Tachycardia-Bradycardia Syndrome. Thyroid function tests indicated primary hypothyroidism, and thyroid ultrasound suggested a diffuse goiter.

Intervention and Results: Treatment with levothyroxine was initiated at 50 mcg/day for 1 week, then increased to 100 mcg/day. This led to a noticeable improvement in heart rate regulation, without new syncopal events. However, a follow-up Holter at 3 months, despite normalized thyroid levels, detected pauses longer than 3 seconds and tachyarrhythmias. The conduction disorder persisted, likely due to apical implantation of the tricuspid valve (VT).

Conclusions: This case illustrates a serious but potentially fatal association between sinus node dysfunction expressed as Bradycardia-Tachycardia syndrome, Ebstein's anomaly, and hypothyroidism. Endocrine disorders like hypothyroidism must be diagnosed and treated promptly, as inadequate management can result in life-threatening cardiovascular changes. Despite normalization of thyroid function, the conduction abnormality remained, and pacemaker implantation was determined to be the definitive treatment for this patient.