Atrial fibrillation propagates through gaps in ablation lines: implications for ablative treatment of atrial fibrillation.
BACKGROUND
It has been hypothesized that atrial lesions must be transmural to successfully cure atrial fibrillation (AF). However, ablation lines often do not extend completely across the atrial wall.


OBJECTIVE
The purpose of this study was to determine the effect of residual gaps on conduction properties of atrial tissue.


METHODS
Canine right atria (n = 13) were isolated, perfused, and mounted on a 250-lead electrode plaque. The atria were divided with a bipolar radiofrequency ablation clamp, leaving a gap that was progressively narrowed. Conduction velocities at varying pacing rates and AF frequencies were measured before and after ablations. AF was induced with an extra stimulus and acetylcholine.


RESULTS
Gap widths from 11.2 to 1.1 mm were examined. Conduction velocities through gaps were dependent cycle length (P = .002) and gap size (P <.001). Overall, 253 (97%) of a total of 260 gaps allowed paced propagation; 51 (91%) of 56 gaps 1-3 mm in width permitted paced propagation, as did 202 (99%) of 204 gaps >or=3.0 mm. Similarly, 253 (97%) of a total of 260 gaps allowed propagation of AF. For AF, 51 (93%) of 55 gaps 1-3 mm allowed AF to pass through, as did 202 (99%) of 205 gaps >or=3.0 mm. Gaps as small as 1.1 mm conducted paced and AF impulses.


CONCLUSIONS
Conduction velocities were slowed through residual gaps. However, propagation of wave fronts during pacing and AF occurred through the majority of residual gaps, down to sizes as small as 1.1 mm. Leaving viable tissue in ablation lines for the treatment of AF could account for failures.
Melby
Spencer J
SJ
Department of Surgery, Division of Cardiothoracic Surgery, Washington University in St. Louis School of Medicine and Barnes Jewish Hospital, St. Louis, Missouri 63110, USA.
Lee
Anson M
AM
Zierer
Andreas
A
Kaiser
Scott P
SP
Livhits
Masha J
MJ
Boineau
John P
JP
Schuessler
Richard B
RB
Damiano
Ralph J
RJ
D000818:Animals; D001281:Atrial Fibrillation / Q000503:physiopathology* / Q000628:therapy*; D017115:Catheter Ablation / Q000295:instrumentation / Q000379:methods; D004195:Disease Models, Animal; D004285:Dogs; D004594:Electrophysiology; D006325:Heart Atria / Q000473:pathology*; D006329:Heart Conduction System / Q000503:physiopathology*; D010865:Pilot Projects
Heart Rhythm. 2004 Dec;1(6):676-83
15851239
J Interv Card Electrophysiol. 2000 Apr;4(1):273-81
10729848
Ann Thorac Surg. 2003 Sep;76(3):836-41; discussion 841-2
12963212
J Thorac Cardiovasc Surg. 2003 Jul;126(1):254-62
12878963
Eur Heart J. 2005 Sep;26(17):1797-803
15855195
Circulation. 1987 Sep;76(3):637-47
3621524
Ann Thorac Surg. 2002 Oct;74(4):S1307-11
12400806
Arch Intern Med. 1995 Mar 13;155(5):469-73
7864703
Circulation. 1998 Jun 2;97(21):2136-45
9626174
Ann Thorac Surg. 2006 Jan;81(1):72-6
16368338
Circulation. 2005 Aug 30;112(9 Suppl):I7-13
16159868
Ann Thorac Surg. 2001 Sep;72(3):S1096-9
11565732
Ann Thorac Surg. 1996 Dec;62(6):1796-800
8957389
Circulation. 2005 Mar 8;111(9):1100-5
15723973
J Cardiovasc Electrophysiol. 1999 Mar;10(3):378-86
10210501
Circulation. 1998 Mar 31;97(12):1176-85
9537344
J Thorac Cardiovasc Surg. 1991 Apr;101(4):569-83
2008095
J Thorac Cardiovasc Surg. 2003 Dec;126(6):1822-8
14688693
Circ Res. 1992 Nov;71(5):1254-67
1394883
J Cardiovasc Electrophysiol. 1996 Dec;7(12):1132-44
8985802