Key result
In a 74-year-old man, His bundle extrasystoles mimicking Wenckebach or Mobitz II block were markedly suppressed by procainamide, though a permanent pacemaker was inserted due to prolonged HV interval.
Case Report (n=1)
His bundle extrasystoles can mimic various arrhythmias and AV blocks on surface ECG, highlighting the importance of EP studies for accurate diagnosis and management.
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Apparent AV block warrants EP study to exclude His bundle extrasystoles; single case leaves open whether procainamide avoids pacing.
A 74-year-old man with past history of near syncope presented with frequent periods of second-degree atrioventricular block (2° AVB). An electrophysiological study revealed prolonged atrial-His and His-ventricular (HV) intervals and frequent His bundle (H) extrasystoles. The latter manifested in the surface electrocardiogram as premature atrial, junctional, or ventricular beats, as well as 2° AVB that mimicked Wenckebach or Mobitz II block. Procainamide markedly suppressed H extrasystole. However, because of the presence of prolonged HV interval and history of presyncope, a permanent pacemaker was inserted. The case illustrates the varied manifestation of H extrasystole and presents guidelines for management.
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Ameen et al. (2010) conducted a case report in His bundle extrasystoles and second-degree atrioventricular block (n=1). Procainamide and permanent pacemaker insertion was evaluated. In a 74-year-old man, His bundle extrasystoles mimicking Wenckebach or Mobitz II block were markedly suppressed by procainamide, though a permanent pacemaker was inserted due to prolonged HV interval.
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