Unresolved Complete Heart Block in a Patient Treated for Euthyroid Graves' Disease: A Diagnostic Dilemma

The cardiovascular implications of thyroid disease have been recognized as one of the most characteristic signs that result from the effect of thyroid hormone (TH). Both hyperthyroidism and hypothyroidism produce changes in cardiac contractility, myocardial oxygen consumption, cardiac output, blood pressure, and systemic vascular resistance. The bradyarrhythmias, including atrioventricular block and sick sinus syndrome, are exceedingly rare in hyperthyroidism.Studies have stated that atrioventricular block complicating a hyperthyroid state is the rarest and most under-studied cardiac complication. Only a few case reports have described this association, which is commonly seen with acute inflammatory states, infections, or medications. Here, we present the case of a 16-year-old girl who presented with thyrotoxicosis and was incidentally found to have asymptomatic complete heart block (CHB) in the setting of newly diagnosed Graves' disease. This case report explores the course of her treatment and possible causes given the rarity of presentation.