Complete Atrioventricular Block Presenting With Syncope Caused by Severe Hypothyroidism

Case Report: Hypothyroidism Misdiagnosed as Fulminant Myocarditis in a Child

Background: Hypothyroidism can lead to bradycardia, reduced cardiac output, cardiac enlargement, and abnormal electrocardiogram. However, hemodynamic instability and malignant arrhythmias due to hypothyroidism is rarely reported in children. Patient Findings: We report the case of a child with third-degree atrioventricular block, cardiogenic shock, and Adams Stokes Syndrome, who was initially misdiagnosed with fulminant myocarditis and was later found to have hypothyroidism during treatment. Summary: The child's condition did not improve after the administration of gamma globulin, methylprednisolone, and isoproterenol. Even after the placement of temporary pacemakers, the therapeutic effect was still not ideal. Upon reviewing the medical history, the child's condition improved rapidly after levothyroxine supplementation. Conclusions: Hypothyroidism is a common disease, but secondary severe cardiovascular lesions are particularly rare in children. Therefore, the delay in diagnosis can lead to serious cardiovascular manifestations. When pediatric patients develop severe AVB and bradycardia, hypothyroidism should be considered as a possible cause.

A Pacemaker that was Avoided

Thyroxine is an essential hormone in the human body and exerts many effects on the cardiovascular system. The low metabolic state in hypothyroidism causes bradycardia and reduced cardiac contractility leading to reduced cardiac output. Severe bradycardia and atrioventricular (AV) blocks secondary to hypothyroidism have also been reported. We present a case of severe hypothyroidism causing a high-grade AV block which was successfully treated with thyroxine hormone replacement without requiring cardiac pacemaker placement.

Acute mania after levothyroxine replacement for hypothyroid-induced heart block

Psychiatric disturbances can manifest after levothyroxine (LT4) treatment for severe hypothyroidism. We present the case of a young Filipino man with Hashimoto's thyroiditis and high-grade heart block, who was given a full replacement LT4 dose on admission. Twenty-four hours after this dose, he developed manic symptoms, which were addressed with sedatives and neuroleptics with gradual restoration of euthymia the following day. A comprehensive workup did not reveal any findings suggestive of another aetiology for either mania or heart block. We ultimately ascribed the mania as secondary to LT4, and the heart block to hypothyroidism. Although mania is more likely to be precipitated by high starting LT4 doses, reports have shown that symptoms can still arise even at lower doses and with more gradual titration, especially in long-standing hypothyroidism.