Refractory Complete Atrioventricular Block Secondary to Hypothyroidism Requiring Permanent Pacemaker

Thyroid hormone regulates the body's metabolism, and its insufficiency can result in a wide variety of manifestations, including fatigue, lethargy, constipation, cold intolerance, and change in voice. Hypothyroidism also affects the cardiovascular system and can cause decreased cardiac output, increased systemic vascular resistance, pericardial effusion, bradycardia, and heart block. Hypothyroidism is a rare cause of complete atrioventricular block (AVB), which is generally thought to be reversible after thyroid replacement therapy. Here, we report a case of a 74-year-old female who presented to our hospital with lower extremity swelling and fatigue. She was diagnosed with hypothyroidism based on her thyroid function test. An electrocardiogram (ECG) revealed a complete AVB, and she was started on thyroid replacement therapy. During the second week of thyroid replacement therapy, she experienced episodes of bradycardia, and ECG still showed a complete AVB; despite normalization of her thyroid function, prompting placement of a pacemaker. The patient was discharged with endocrinology and electrophysiologist (EP) follow-upi