A 73-year-old man was referred from another hospital to our department for permanent pacemaker implantation due to persistent (more than 3 days) complete atrioventricular (AV) block. His past medical history included history of hyperthyroidism under treatment with carbimazol 2.5 mg once daily. On admission, serum thyroxin stimulating hormone concentration was <0.01 μIU/ml (normal 0.35-4.95 μIU/ml). Antithyroid drug treatment was intensified. Five days after admission complete heart block persisted on ECG, but 1 week later the ECG revealed a junctional rhythm, which resolved to first degree AV block on the tenth day of hospitalization and the patient was discharged. Subsequent follow up at 3 months after discharge with 24-hour holter recording, revealed normal sinus rhythm without any conduction disturbances
