Pulmonary veins and ligament of Marshall as sources of rapid activations in a canine model of sustained atrial fibrillation.
BACKGROUND
In dogs, chronic rapid pacing may result in sustained atrial fibrillation (AF). However, activation patterns in pacing-induced sustained AF are unclear.


RESULTS
We induced sustained AF (>48 hours) in 6 dogs by rapid pacing for 139+/-84 days. We then performed computerized atrial epicardial mappings and recorded the activations in the ligament of Marshall (LOM) and the pulmonary veins (PVs). During AF, mean activation cycle length in the right atrial free wall (126+/-17 ms) was significantly longer than that in the left atrial free wall (96+/-5 ms, P:=0.006). In addition, mean activation cycle length in the left atrial free wall was significantly longer than that in the LOM (84+/-5 ms, P:<0.001), the left inferior PV (81+/-4 ms, P:=0.001), and the left superior PV (85+/-7 ms, P:=0.003). Similarly, the dominant frequency was highest in the LOM and the PVs (range 11.2 to 13.3 Hz), followed by the left and right atria (P:<0.001). In all dogs studied, rapid and complicated electrograms were consistently observed at the LOM and the PVs. During AF, both wandering wavelets and organized reentry were present. There were more wave fronts in the left atrium than in the right atrium (P:<0.001).


CONCLUSIONS
In chronic pacing-induced sustained AF, the LOM and the PVs are the sources of rapid activations. The mechanism by which the left atrium activates faster and has more wave fronts than the right atrium may relate to the fact that the left atrium is closer to the sources of rapid activations.
Division of Cardiology, Department of Medicine, Taichung Veterans General Hospital and Institute of Clinical Medicine, National Yang-Ming University School of Medicine, Taipei, Taiwan.
T J
TJ
Wu
J J
JJ
Ong
C M
CM
Chang
R N
RN
Doshi
M
M
Yashima
H L
HL
Huang
M C
MC
Fishbein
C T
CT
Ting
H S
HS
Karagueuzian
P S
PS
Chen
D000704:Analysis of Variance; D000818:Animals; D001281:Atrial Fibrillation / Q000209:etiology / Q000473:pathology / Q000503:physiopathology*; D016275:Atrial Function; D002304:Cardiac Pacing, Artificial / Q000009:adverse effects; D002908:Chronic Disease; D004285:Dogs; D004554:Electric Countershock; D006329:Heart Conduction System / Q000502:physiology; D008022:Ligaments / Q000502:physiology*; D011667:Pulmonary Veins / Q000502:physiology*