[Ventricular pre-excitation disclosed by an episode of high-frequency atrial fibrillation: the role of frequency-dependent variations in the bundle of Kent conduction].
The presence of a ventricular pre-excitation, which becomes evident only during episodes of atrial fibrillation, is a very rare event. The authors report a case of ventricular pre-excitation revealed by an access of atrial fibrillation with high ventricular frequency and hemodynamic failure. The ventricular pre-excitation signs were not evident after the sinus rythm had been restored. The electrophysiological study has shown that such behaviour is not related to a different input of the stimulus in the bypass tract during the passage from the sinus rhythm to the atrial fibrillation, as other authors have recently suggested, but to rate-dependent variations of the conduction in the Kent bundle: in the bypass either a phase-4 block of the conduction is present, or a supernormal conduction.