Catecholamine Dependent Accessory Pathway Automaticity

Abstract

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.

Automaticity with anterograde conduction of a concealed accessory pathway due to radiofrequency energy application

“…Accelerated automatic rhythm is also a well-known response of atriofascicular pathways to thermal injury during RF ablation being another argument for the presence of an AV nodal-like structure in atriofascicular pathways. What is very uncommon is the occurrence of automaticity of rapidly conducted APs in response to RF energy application [1][2][3]. In our case two different wide QRS complex rhythms, one regular (Fig.…”

“…Automaticity of rapidly conducting atrioventricular accessory pathways (AP) in response to radiofrequency (RF) energy application is a very uncommon observation [1][2][3]. On the other hand, emergence of ventricular preexcitation following RF application in concealed accessory pathways is one other rare electrophysiologic phenomenon that has been previously reported, the mechanism of which is poorly understood [4,5].…”

Look and you shall find: Perils along the road after slow pathway ablation for AV nodal reentry tachycardia

“…Ablation of the accessory pathway usually results in disappearance of both arrhythmias; however, on rare occasions the PVCs and wide QRS complex tachycardia may persist despite the absence of antegrade preexcitation . A similar phenomenon has been observed subsequent to ablation of a para‐Hisian accessory pathway . These scenarios highlight the fact that both automaticity and conduction may be an inherent property of the conduction pathways underlying supraventricular arrhythmias of the heart …”

Wide QRS Complex Tachycardia in a Patient With Concealed Accessory Pathway: What Is the Mechanism?

“…Reports describing spontaneous activity in accessory pathways mainly deal with atriofascicular pathways; due to AV‐node‐like physiology, these pathways not infrequently show spontaneous and heat‐induced automaticity . However, we found only four reports concerning manifest automaticity in a regular atrioventricular AP . Compared with these patients, ours is unique in 2 ways.…”

“…Compared with these patients, ours is unique in 2 ways. In 2 of these patients, automaticity was not spontaneous but was provoked by ablation, with the arrhythmias appearing after ablation not reliably differentiated from the ventricular rhythm arising from a nearby focus, as there was no retrograde conduction and resulting preceding atrial activation, as in our patient. In the other 2 patients the arrhythmias could not be differentiated from atrial foci adjacent to the AP as the AP was overt, rather than concealed as in our patient.…”