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Europace Advance Access published online on July 13, 2007
Europace, doi:10.1093/europace/eum108
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© The European Society of Cardiology 2007. All rights reserved. For Permissions, please e-mail: journals.permissions@oxfordjournals.org

Difference between electrical remodelling after pulmonary veins and right atrium appendage pacing

Kebbati A. Hafid, Huang Cong Xin*, Wang Xi, Zhao Qing Yan and Yang Bo

Department of Cardiology, Renmin Hospital of Wuhan University, Jiefang Road 238, Wuhan 430060, People's Republic of China

Objective Pulmonary veins (PVs) are important sources of paroxysmal atrial fibrillation (AF). Rapid atrial pacing changes atrial electrophysiology, and facilitates the induction and maintenance of AF. The purpose of our study was to evaluate the changes in atrial effective refractory period (AERP) proprieties and in ionic currents in PVs myocytes from dogs subjected to rapid atrial pacing in PVs and right atrial appendage (RAA) and to relate these changes to the ability to induce AF.

Methods Twelve mongrel dogs in normal sinus rhythm were paced from the superior left PVs or RAA at 500 bpm for 4 h. Electrophysiological studies were conducted to determine the changes in AERP, dispersion, and rhythm. Ionic currents were evaluated using patch clamp technique in single PVs myocytes in sham-operated dogs, and the results were compared with those from PVs and RAA pacing groups.

Results The presence of rapid atrial pacing was associated with a marked shortening in AERP in both PVs and RAA pacing group with a marked increase in AERP dispersion in PVs pacing. Both L-type calcium current (ICa,L) and the transient outward current (Ito) were reduced in both groups with an increased significance in PVs pacing group. The density of ICa,L was decreased significantly from (–6.03 ± 0.63) pA/pF in the control group to (–3.21 ± 0.34) pA/pF in the PVs pacing group and (–4.75 ± 0.41) pA/pF in the RAA pacing group (n = 6, P < 0.05), whereas the density of Ito was decreased significantly from (8.45 ± 0.71) pA/pF in the control group to (5.21 ± 0.763) pA/pF in the PVs pacing group and (6.84 ± 0.69) pA/pF in the RAA pacing group (n = 6, P < 0.05).

Conclusion Our findings provide likely ionic mechanisms of shortened repolarization in induced atrial tachycardia with a decrease in ICa,L and Ito densities, which is the likely mechanism for a decrease in action potential duration rate adaptation in the canine rapid pacing model more pronounced in the PVs pacing group underlying the crucial role of PVs in initiating AF.

Key Words: Pulmonary vein, Atrial fibrillation, Ca2+ channel, K+ channel, Remodeling, Canine

* Corresponding author. Tel: +86 276 295 9239; fax: +86 27 88040334. E-mail address: huangcongxin{at}yahoo.com.cn

Manuscript submitted 13 November 2006. Accepted after revision 26 April 2007.


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