Masquerading bundle branch block: an often missed electrophysiological event.

Masquerading bundle branch block is an easily overlooked pattern on the ECG that indicates severe disease of the atrioventricular nodal conduction pathway. It is often caused by coronary artery disease, infiltrative diseases of the heart and idiopathic degeneration of the atrioventricular nodal conduction pathways. The diagnosis is easily missed as it needs a detailed interpretation of the ECG in addition to the clinical presentation of the patient. The presence of this specific bundle branch block pattern on the ECG indicates severe degeneration of the conduction system requiring intervention. Given its rarity, this clinical entity risks misdiagnosis and inappropriate management. This case highlights two diagnostic challenges for clinicians: the rarely described masquerading bundle branch block and the art of clinically differentiating between epilepsy and convulsive syncope.