Transient entrainment and interruption of the atrioventricular bypass pathway type of paroxysmal atrial tachycardia. A model for understanding and identifying reentrant arrhythmias.

Abstract

SUMMARY We studied transient entrainment and interruption of atrioventricular (AV) bypass pathway-type paroxysmal atrial tachycardia in 15 patients during overdrive pacing from selected atrial sites. Overdrive atrial pacing at less than a critically rapid rate for interruption transiently entrained the tachycardia. Transient entrainment was due to repeated early entrance of the wave front from the pacing impulse into the reentry loop in both antidromic and orthodromic directions. The antidromic wave front of each pacing impulse was repeatedly blocked as it collided with the orthodromic wave front of the previous beat, in effect extinguishing the tachycardia. However, the early entrance of the orthodromic wave front of each pacing impulse repeatedly reset the tachycardia. The result was that during transient entrainment, the tachycardia rate increased to the pacing rate. Interruption of the tachycardia occurred when overdrive pacing produced block within the reentry loop of both the antidromic and orthodromic wave fronts of the same pacing impulse, the block occurring either at separate sites within the reentry loop or at the same site. Atrial fusion beats were demonstrated during transient entrainment in nine patients and resulted from intraatrial collision of the antidromic wave front from the pacing impulse with the orthodromic wave front of the previous beat. The presence offusion beats depended critically on the relationship of the pacing site to the reentry loop and the duration of conduction around the reentry loop, particularly through the area of slow conduction.The data from this study suggest that (1) if one can demonstrate constant fusion beats during transient entrainment of a tachyarrhythmia except for the last transiently entrained beat; or (2) if during transient entrainment of a tachyarrhythmia at two or more different pacing rates, one can demonstrate constant fusion at each of the different pacing rates, but different degrees of fusion at the different rates; or (3) if interruption of a tachyarrhythmia by overdrive pacing is associated with localized conduction block to a site followed by activation of that site by the next pacing impulse from a different direction and with a shorter conduction time, then the underlying mechanism of the arrhythmia can be best explained by reentry.PAROXYSMAL atrial tachycardia that involves antegrade conduction from the atria through the atrioventricular (AV) node-His-Purkinje system to the ventricles with retrograde conduction from the ventricles via an AV bypass pathway back to the atria is the best understood example of putative reentrant rhythms.1AThis arrhythmia is often found in patients with the Wolff-Parkinson-White syndrome and in patients with a so-called concealed AV bypass pathway, i.e., one that conducts only in the retrograde direction. The many types of treatment for this arrhythmia include its interruption by overdrive cardiac pacing.' We have found that overdrive pacing used to interrupt paroxysmal atrial tachycardia of this variety has much in ...

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

“…[1][2][3][4][5][6][7][8][9][10][11]18 They confirm the reliability of the three proposed criteria for its identification, demonstrate and explain that both transient entrainment and interruption of a tachyarrhythmia may occur without fulfilling any of the three criteria (concealed entrainment), permit localization of an area of slow conduction within the reentry loop relative to the pacing site, and force a reexamination of the third criterion concerning localized conduction block associated with interruption of the tachycardia.…”

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

“…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). When manifest entrainment with orthodromic capture of the EAAS was demonstrated, the pacing site was considered to be proximal to the SCZ of the reentry circuit13 (entrainment pacing site; Figure 1). Rapid pacing was delivered from 8 sites on the RA: high anterolateral RA; high posterolateral RA; high anteroseptal RA; high posteroseptal RA; low anterolateral RA; low posterolateral RA; low posteroseptal RA; and CS ostium.…”

CKD and Sudden Cardiac Death

“…Fibrosis disrupts the normal myocardial architecture and results in a slowing of conduction velocity across the diseased tissue. 63 This pathology can form heterogeneous zones of conduction and repolarization that can sustain a re-entrant arrhythmia such as ventricular tachycardia. 51,53,64 These structural changes impair cardiac conduction, delay ventricular activation, and create late potentials in the terminal portion of the QRS complex.…”