Concealed His Extrasystoles: A Masquerader of Atrioventricular Block

Concealed His extrasystoles are a well-known masquerader of atrioventricular (AV) block. It is therefore necessary to consider pseudo-AV block in patients who develop unexpected AV block without a clear etiology. In this report, we present a case of a 46-year-old female patient who was found to have pseudo–Mobitz II AV block secondary to His extrasystoles diagnosed on surface electrocardiogram (ECG) without requiring invasive electrophysiology study. We also demonstrated in this patient that flecainide can be an effective treatment for His extrasystoles.