Reentry in an accessory atrioventricular pathway as a trigger for atrial fibrillation initiation in manifest Wolff-Parkinson-White syndrome: a matter of reflection?
BACKGROUND
Patients with an accessory pathway (AP) have an increased propensity to develop atrial fibrillation (AF), but the mechanism is unknown.


OBJECTIVE
The purpose of this study was to identify crucial risk factors and to test the hypothesis that reflection and/or microreentry of atrial impulses propagating into the AP triggers AF.


METHODS
Five hundred thirty-four patients successfully treated with radiofrequency ablation of AP at two university hospitals were evaluated. Patients were separated into those with concealed vs those with manifest AP in terms of their propensity to develop AF. To investigate AF triggering mechanisms, linear and branched two-dimensional models of atrium-to-ventricle propagation across a heterogeneous 1 x 6 AP using human ionic kinetics were simulated.


RESULTS
A history of AF was twice as common in patients with manifest AP vs concealed AP irrespective of AP location. AF was more likely to occur in older males and in patients with larger atria. There was no correlation between AF history and AP refractory measures. However, the electrophysiologic properties of APs seemed to fulfill the prerequisites for reflection and/or microreentry of atrially initiated impulses. In the linear AP model, repetitive atrial stimulation resulted in progressively larger delay of atrium-to-ventricle propagation across the passive segment. Eventually, sufficient time for repolarization of the atrial segment allowed for reflection of an impulse that activated the entire atrium and by wavefront-wavetail interaction with a new atrial stimulus AF reentry was initiated. Simulations using the branched model showed that microreentry at the ventricular insertion of the AP could also initiate AF via retrograde atrial activation as a result of unidirectional block at the AP-ventricle junction.


CONCLUSIONS
Propensity for AF in patients with an AP is strongly related to preexcitation, larger atria, male gender, and older age. Reflection and microreentry at the AP may be important for AF initiation in patients with manifest (preexcited) Wolff-Parkinson-White syndrome. Similar mechanisms also may trigger AF in patients without an AP.
Schwieler
Jonas H
JH
Department of Cardiology, Karolinska University Hospital, Karolinska Institutet, Stockholm, Sweden.
Zlochiver
Sharon
S
Pandit
Sandeep V
SV
Berenfeld
Omer
O
Jalife
José
J
Bergfeldt
Lennart
L
D000328:Adult; D000367:Age Factors; D001281:Atrial Fibrillation / Q000209:etiology / Q000503:physiopathology* / Q000601:surgery; D001283:Atrioventricular Node / Q000503:physiopathology* / Q000601:surgery; D017115:Catheter Ablation; D003198:Computer Simulation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D012737:Sex Factors; D013997:Time Factors; D014927:Wolff-Parkinson-White Syndrome / Q000503:physiopathology*
Circ Res. 1989 Dec;65(6):1612-31
2582593
Circulation. 1980 Jan;61(1):182-91
7349933
Circ Res. 1981 Jul;49(1):233-47
7237694
Europace. 2002 Apr;4(2):201-6
12135254
Circ Res. 1992 Aug;71(2):260-70
1628385
Eur Heart J. 2001 Mar;22(5):423-7
11207084
Circ Res. 2007 Oct 12;101(8):839-47
17704207
Circulation. 1990 Aug;82(2):407-17
2372891
Circulation. 1995 Oct 1;92(7):1954-68
7671380
J Cardiovasc Electrophysiol. 2007 Apr;18(4):451-4
17284260
Int J Cardiol. 2006 Jan 4;106(1):75-81
16321670
J Am Coll Cardiol. 1991 May;17(6):1352-6
2016453
J Physiol. 1952 Nov;118(3):348-60
13000763
J Physiol. 1913 Jul 18;46(4-5):349-83
16993210
Heart Rhythm. 2007 Mar;4(3 Suppl):S13-6
17336877