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.

Current guidelines necessitate varying degrees of long-term anticoagulation in patients with mechanical heart valve(s) to prevent thrombotic and embolic complications. We describe a patient with a functioning aortic mechanical valve without anticoagulation for 23 years. A 68-year-old man had an aortic valve (St Jude Medical) replacement in 1984. His native valve was incompetent from infective endocarditis. He discontinued Coumadin three months after the surgery. He presented 23 years later with palpitations for one month. Further work-up revealed a NYHA class I function, normal sinus rhythm, normal sized heart on chest X-ray, normal systolic and diastolic function on echocardiography. Mean transaortic gradient was 19 mmHg and calculated valve area was 1.48 cm(2). Fluoroscopy showed normal excursions of the mechanical aortic valve. Exercise stress test did not show any limitation in effort tolerance or perfusion defects. He was discharged on daily aspirin and clopidogrel.

An 84 year-old man with history of recurrent dizziness presented with first degree atrio-ventricular block (1° AVB) and periods of 2:1 AVB. An electrophysiological study revealed a predominant 1:1 AV conduction with markedly prolonged AH interval and frequent His bundle extrasystoles (H). A properly timed H could induce periods of 2:1 AV nodal block and 1:1 AV conduction could only resume following another properly timed H. Procainamide suppressed H. However, because of persistence of the patient symptoms, a permanent pacemaker was eventually inserted. The case illustrates a hitherto not described manifestation of H.

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