Further observations on transient entrainment: importance of pacing site and properties of the components of the reentry circuit.

Abstract

Transient entrainment of circus-movement tachycardia utilizing an atrioventricular (AV) bypass pathway was studied in 13 patients (nine with the orthodromic form, two with the antidromic form, and two with both the orthodromic and antidromic forms). All patients had a leftsided AV bypass pathway. Pacing at selected rates faster than the spontaneous rate was performed during the tachycardia at a site proximal or distal to the AV node, an area of slow conduction within the reentry loop. Rapid pacing from a site proximal to the AV node (from the right atrium during the orthodromic form of the arrhythmia or the right ventricle during the antidromic form of the arrhythmia) always demonstrated at least one of the three entrainment criteria: constant fusion beats except for the last captured beat, which was entrained but not fused (first criterion); progressive fusion (second criterion); localized conduction block to a site(s) for 1 paced beat associated with interruption of the tachycardia followed by activation of that site(s) by the next paced beat from a different direction and with a shorter conduction time (third criterion). In contrast, rapid pacing from a site distal to the AV node (from the right ventricle during the orthodromic form of the arrhythmia, or the right atrium during the antidromic form of the arrhythmia) transiently entrained the tachycardia, but never demonstrated any entrainment criteria because the antidromic wave front from the pacing impulse always blocked in the AV node (concealed entrainment). We conclude that the location of the pacing site relative to the components of a reentry loop is critical to the demonstration of the criteria of transient entrainment; i.e., if it is proximal to an area of slow conduction and/or unidirectional block within a reentry loop, transient entrainment should be demonstrable, but if it is distal, it will not be demonstrable. Circulation 72, No. 6, 1293-1307, 1985 TRANSIENT ENTRAINMENT of a tachycardia during rapid pacing is an increase in rate of the tachycardia to the faster pacing rate, with resumption of the intrinsic rate of the tachycardia on either termination of pacing or slowing of the pacing rate below the intrinsic rate of the tachycardia. '-'°We, and subsequently other investigators, have presented evidence that this is best explained by continuous early entrance of the wave front from the pacing impulse into the excitable gap of a tachycardia's reentry loop.

Slow Potential at the Entrance of the Slow Conduction Zone in the Reentry Circuit of a Verapamil‐Sensitive Atrial Tachycardia Originating From the Atrioventricular Annulus

“…Furthermore, the EAAS was orthodromically captured during manifest entrainment. Orthodromic capture of the EAAS during manifest entrainment implies that there is an area of slow conduction within the reentry circuit between the entrance and exit sites 11, 12. Satoh et al15 clearly demonstrated that orthodromic capture of the EAAS implies the presence of an entrance and an exit to the atrium located at distinct different locations.…”

“…Details of the EnSite 3000 system have been previously described 10. The proximity of the SCZ in the reentry circuit was identified utilizing an entrainment technique 11. While recording the contact atrial electrogram at the EAAS, rapid atrial pacing at a rate 5 beats per minute faster than the tachycardia rate was delivered to demonstrate manifest entrainment and orthodromic capture of the EAAS12 (Figure 1).…”

Electrical Remodeling of the Atrium in an Anatomic Model of Atrial Flutter

“…AFL was defined as a macroreentrant atrial tachycardia displaying (1) typical "sawtooth" flutter wave appearance on the surface ECG with a constant morphology, (2) entrainment criteria, 11,12 with demonstration of an excitable gap, and (3) a regular and constant epicardial atrial activation pattern (ie, no change in sequence) recorded from the 3 epicardial electrode plaques.…”

Orthodromic capture of the atrial electrogram during transient entrainment of atrioventricular nodal reentrant tachycardia.

“…When the first postpacing interval was the same as the paced cycle length, the atrial electrogram at the recording site of the His bundle potential was considered to be captured orthodromically. [14][15][16][17] Results…”