Masquerading bundle branch block as a marker of poor prognosis.

Masquerading bundle branch block is a rare and unique finding on a 12-lead electrocardiogram, consisting of the pattern of right bundle branch block in the precordial leads and left bundle branch block in the limb leads. We experienced a 77-year-old woman with masquerading bundle branch block. She had been well, but died suddenly 9 months after the diagnosis of masquerading bundle branch block. The presence of masquerading bundle branch block indicates severe degeneration of the conduction system, leading to a poor outcome. <Learning objective: Masquerading bundle branch block is a rare and unique finding on a 12-lead electrocardiogram, consisting of the pattern of right bundle branch block in the precordial leads and left bundle branch block in the limb leads. The presence of masquerading bundle branch block indicates severe degeneration of the conduction system, leading to a poor outcome. Close follow-up is mandatory in patients with masquerading bundle branch block even if they do not have any symptoms.>.