Graves' Disease Presenting with Complete Atrioventricular Bl
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A 28-year-old female patient had presented with dizziness a week ago. While she was waiting for medical consultation at a primary care clinic, she suddenly lost consciousness and had involuntary convulsive-like movements for 10 seconds. She had a history of acute otitis media 7 days ago and had taken medications including antibiotics for 3 days. The electrocardiogram performed at the primary care clinic showed complete AV block with supraventricular rhythm, followed by long ventricular asystole over 4.4 seconds. Initial blood pressure and pulse rate were 128/70 mmHg and 30 per minute, respectively.

Follow-up electrocardiography at the emergency room revealed complete AV block with the ventricular escape rhythm. A temporary transvenous ventricular pacing was applied through the internal jugular vein. Serum electrolyte levels were within the normal clinical range, and renal function was normal. She did not take other or herbal medications except for drugs for acute otitis media including cefditoren, erdosteine, and levocetirizine. The thyroid gland was diffusely enlarged, and bilateral exophthalmos was identified. The level of the thyroid-stimulating hormone was very low, less than 0.008 IU/mL, and the levels of free T4 and T3 were 6.4 ng/dL and 511.0 ng/dL, respectively.

Propylthiouracil 300 mg daily was started. Thyroid ultrasound noted diffuse thyroid enlargement with heterogenous parenchymal echogenicity. Radioiodine scan showed intense increased thyroid uptake, consistent with hyperthyroidism. Echocardiography reported normal cardiac function without structural abnormalities. Coronary computed tomography angiography or cardiac catheterization was not performed because she did not have any risk factors for coronary artery disease, and myocardial ischemia was less likely to be the cause of complete AV block in this patient. At the eighth hospital day, the levels of free T4 and T3 decreased to 2.9 ng/dL and 222.3 ng/dL, respectively. Complete AV block was recovered to sinus rhythm with rates of 75 per minute, and transvenous pacing lead was removed. She was discharged with medications for hyperthyroidism without the recurrence of the AV block.