Atrioventricular nodal fast pathway modification: mechanism for lack of ventricular rate slowing in atrial fibrillation

Abstract

Despite its longer ERP, FP is responsible for a substantial number of ventricular beats during AF. However, selective FP ablation has a minor effect on ventricular rate. The most likely mechanism for this phenomenon is that FP ablation allows previously concealed SP beats to be conducted. On the other hand, ventricular rate slowdown could be achieved if FP ablations caused collateral damage in the compact node. This study highlights the usefulness of HE alternans as a novel tool to monitor dual pathway conduction during AF and to guide AVN modification.

Characterization and Modeling of Atrioventricular Conduction during Atrial Fibrillation

“…In figure 2.6 an example of high-low IHE alternans recorded during experimental AF in rabbit heart preparation [44,45,46]. Successful SP modification prolonged the AV node ERP without changing the basic AV node conduction time, which is consistent with clinical SP ablation [3].…”

“…In rabbit heart experiments it was shown that this index could be used to determine on a beat-by-beat basis during AF the AV node conduction pattern (i.e. though FP or SP) [44,45,46]. Specifically, a low amplitude inferior bundle of His electrogram (IHE) was associated with FP conduction, while high-amplitude IHE indicates SP conduction.…”

“…However, the study of RR interval series with the Poincaré analysis does not provide direct evidence of the dual pathways [60,41]. It is unclear whether the two pathway properties can be evaluated from the two distributions of the Poincaré plot and the role of the second pathway in the conduction curve needs to be clarified [3,47,44,45,46]. In fact, during the development of the current thesis we have attempted to clarify which are the mechanisms producing the existence of more than one RR interval distribution and the relation between the dual AV nodal pathway physiology and the ventricular response pattern during AF.…”

“…This index was validated during programmed electrical stimulation (e.g. generation of AV node conduction curve), as well as during atrial arrhythmia [44,45,46].…”

“…In fact, the evaluation of their individual impact on the AV nodal conduction was ambiguous since the pathway responsible for the conduction of a particular beat could not be identified. Recently Zhang et al have introduced the His Electrogram Alternance (HEA) [44,45,46], a recording technique which allows the identification of the dominant pathway and consequently the evaluation of the role of each pathway during AV nodal conduction.…”