Catecholamine dependent accessory pathway automaticity.

Automaticity from extra nodal accessory pathways appears to be rare. We report the case of a man with the WPW syndrome who presented for repeat electrophysiological study and catheter ablation. After successful ablation of a para-Hisian accessory pathway, an isoproterenol challenge produced an accelerated wide complex rhythm that was dissociated from sinus rhythm and matched the previous pattern of maximal preexcitation. This automatic rhythm was transient and dependent on catecholamine administration. One month after successful ablation, an exercise treadmill test (ETT) did not demonstrate any pre-excitation or ectopy.