Automaticity of the Kent bundle: confirmation by phase 3 and phase 4 block

Automaticity in the Kent anomalous atrioventricular bundle has been postulated to occur on the basis of electrocardiographic recordings. This hypothesis was confirmed using intracardiac recordings and programmed stimulation in a patient with pre-excitation. It was supported, in part, by demonstrating the presence of phase 3 and phase 4 block in the Kent bundle during decremental atrial pacing. The existence of automaticity in the Kent bundle may explain the manifestation of intermittent pre-excitation in certain patients. Furthermore, the presence of phase 3 and phase 4 block makes the likelihood of rapid antidromic conduction over the Kent bundle pathway unlikely within this subgroup.