RADIOFREQUENCY CATHETER ABLATION OF THE ATRIA ELIMINATES PACING-INDUCED SUSTAINED ATRIAL-FIBRILLATION AND REDUCES CONNEXIN-43 IN DOGS

Background We assessed the effects of radiofrequency catheter ablation (RFCA) of the atrial epicardium on pacing-induced sustained atrial fi brillation (AF) and the expression and distribution of the intercellul ar gap junction protein connexin 43 (Cx43) in dogs. Methods and Result s In 12 mongrel dogs, after creation of complete AV block and implanta tion of a ventricular inhibited pacemaker, a high-rate pulse generator (20 to 30 Hz to induce AF) was implanted in the neck, connected to a right atrial endocardial pacing lead, and used to pace the atrium for 10 to 14 weeks. In group 1 (n=9 dogs), corrected sinus node recovery t ime (CSNRT), P-wave duration, 24-hour Holler EGG, maximal heart rare ( MHR) in response to isoproterenol, and intrinsic heart rate (IHR) afte r atropine (0.04 mg/kg) and propranolol were measured before and after atrial pacing and RFCA. Group 2 dogs were used to assess the effect o f chronic AF alone on Cx43 expression and distribution. All group 1 do gs developed sustained (>24 hours) AF. Right-sided RFCA of the atria e liminated the sustained AF in 5 dogs, but both right and left atrial R FCA was required to abolish sustained AF in the other 4 dogs. After RF CA restored sinus rhythm, CSNRT and P-wave duration were prolonged and MHR and IHR were decreased. Chronic rapid atrial pacing (group 2) inc reased the expression of Cx43, which was absent in ablated areas and m arkedly depressed in viable atrial myocytes near the ablation zones (g roup 1). Conclusions Rapid atrial pacing for long time periods induced sustained AF that can be eliminated by linear right and left atrial l esions created with RFCA, with preservation of sinus rhythm and atrial contractile function. Chronic AF increased the expression and distrib ution of gap junction protein Cx43, which became reduced in ablated an d nearby nonablated areas.