A 31-year-old man is referred to the EP Clinic because of 3 episodes of palpitation in the past year, with very rapid precordial pounding, chest discomfort, faintness, and 2 brief episodes of loss of consciousness. The arrhythmia is treated with Adenosine:

• Sinus rhythm
  
• Wolff-Parkinson-White (right posteroseptal accessory pathway)
  

Comments: EP studies confirmed the presence of a right posteroseptal accessory pathway. Atrioventricular re-entrant tachycardia with very rapid rate (240/min) was easily induced. After several ablation attempts, retrograde conduction via the pathway was abolished and the arrhythmia could no longer be induced, even after isoproterenol infusion. The antegrade conduction through the pathway, however, persisted and the WPW pattern in the ECG remained unchanged. The procedure was terminated without complications.