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.