Outer loop and isthmus in ventricular tachycardia circuits: Characteristics and implications.
Circuit
Conduction velocity
Electrograms
Mathematical models
Outer loop
Ventricular tachycardia
Journal
Heart rhythm
ISSN: 1556-3871
Titre abrégé: Heart Rhythm
Pays: United States
ID NLM: 101200317
Informations de publication
Date de publication:
10 2020
10 2020
Historique:
received:
08
01
2020
revised:
06
05
2020
accepted:
27
05
2020
pubmed:
5
6
2020
medline:
15
9
2021
entrez:
5
6
2020
Statut:
ppublish
Résumé
The isthmus of ventricular tachycardia (VT) circuits has been extensively characterized. Few data exist regarding the contribution of the outer loop (OL) to the VT circuit. The purpose of this study was to characterize the electrophysiological properties of the OL. Complete substrate activation mapping during sinus rhythm (SR) and full activation mapping of the VT circuit with high-density mapping were performed. Maps were analyzed mathematically to reconstruct conduction velocities (CVs) within the circuit. CV >100 cm/s was defined as normal and <50 cm/s as slow. Electrograms along the entire circuit were analyzed for fractionation, duration, and amplitude. Six postmyocardial infarction patients were enrolled. The VT circuit was a figure-of-eight reentrant circuit in 4 patients and a single-loop circuit in 2 patients. The OL exhibited a mean of 1.9 ± 0.9 and 1.6 ± 0.5 corridors of slow conduction (SC) during VT and SR, respectively. SC in the OL were longer and faster than SC in the isthmus during SR. At the OL, SC sites showed local abnormal ventricular activity in 92%, and a bipolar voltage <0.5 mV was identified in 80.7%. Of the double-loop circuits, only 1 patient had fixed lines of block as isthmus boundaries, whereas in 3 patients the circuits were at least partially functional. In ischemic reentrant VT circuits, the OL contributes significantly to reentry with multiple corridors of SC. These corridors can result from structural or functional phenomena. Isthmus boundaries may correspond to functional or fixed lines of block.
Sections du résumé
BACKGROUND
The isthmus of ventricular tachycardia (VT) circuits has been extensively characterized. Few data exist regarding the contribution of the outer loop (OL) to the VT circuit.
OBJECTIVE
The purpose of this study was to characterize the electrophysiological properties of the OL.
METHODS
Complete substrate activation mapping during sinus rhythm (SR) and full activation mapping of the VT circuit with high-density mapping were performed. Maps were analyzed mathematically to reconstruct conduction velocities (CVs) within the circuit. CV >100 cm/s was defined as normal and <50 cm/s as slow. Electrograms along the entire circuit were analyzed for fractionation, duration, and amplitude.
RESULTS
Six postmyocardial infarction patients were enrolled. The VT circuit was a figure-of-eight reentrant circuit in 4 patients and a single-loop circuit in 2 patients. The OL exhibited a mean of 1.9 ± 0.9 and 1.6 ± 0.5 corridors of slow conduction (SC) during VT and SR, respectively. SC in the OL were longer and faster than SC in the isthmus during SR. At the OL, SC sites showed local abnormal ventricular activity in 92%, and a bipolar voltage <0.5 mV was identified in 80.7%. Of the double-loop circuits, only 1 patient had fixed lines of block as isthmus boundaries, whereas in 3 patients the circuits were at least partially functional.
CONCLUSION
In ischemic reentrant VT circuits, the OL contributes significantly to reentry with multiple corridors of SC. These corridors can result from structural or functional phenomena. Isthmus boundaries may correspond to functional or fixed lines of block.
Identifiants
pubmed: 32497763
pii: S1547-5271(20)30532-4
doi: 10.1016/j.hrthm.2020.05.034
pii:
doi:
Types de publication
Journal Article
Langues
eng
Sous-ensembles de citation
IM
Pagination
1719-1728Informations de copyright
Copyright © 2020 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.