Lown-Ganong-Levine Syndrome in a Patient with Hyperthyroidism

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Introduction: Hyperthyroidism is a serious medical disorder that can be life threatening and is characterized by a sympathovagal imbalance that can be a cause of rapid AF. However, the electrophysiological characteristics of preexcitation syndrome under hyperthyroid condition are unknown. Methods: N/A. Results: We experienced Lown-Ganong-Levine Syndrome (LGLS) in a 49-year-old woman with Graves’ hyperthyroidism. She could not continue to take 1-Methyl-2-mercaptoimidazole because of agranulocytosis and liver dysfunction. Therefore, fractioned radioiodine therapy, radiation, and steroid were started to control hyperthyroidism (TSH: <0.1 microIU/mL; free T3: >32.6 to 6.3 pg/mL; free T4: >7.77 to 3.57 ng/dL). ECG showed short PR interval with normal QRS interval without any delta-wave. She received propranolol to reduce highly symptomatic sinus tachycardia. The electrophysiological study demonstrated atrio-His bypass tract (James bundle) with highly enhanced atrioventricular conduction (1:1 conduction: >300 bpm; ERP: 200 ms). We localized the earliest atrial activation site during RVP as James bundle site at left mid septum, and delivered temperature-controlled RF energy (<10 W) on James bundle site. Only 1 RF pulse successfully eliminated atrio-His bypass without any complication and recurrence (follow-up 15 months). Conclusion: LGLS combined with hyperthyroidism demonstrated highly enhanced atrio-ventricular conduction. Careful RF application to James bundle was feasible to cure preexcitation and normalize atrio-ventricular conduction.