TRANSCATHETER MODIFICATION OF THE ATRIOVENTRICULAR NODE IN DOGS, USING RADIOFREQUENCY ENERGY

Objective-To develop a protocol for reliably inducing atrioventricular (AV) block (ideally first- or second-degree), using radiofrequency en ergy. Design-An electrosurgical unit was coupled to an ammeter, which was connected to the distal pole of an electrode catheter positioned a t the AV node. Control settings had previously been calibrated to the power output in a circuit with a 100-ohm resistance. Animals-10 clinic ally normal dogs. Procedure-Transcatheter AV nodal modification was at tempted, using progressive power applications of 10 to 20 W for progre ssive durations of 10 to 30 seconds, Atrioventricular nodal conduction and refractivity were measured before and 20 minutes and 1 month afte r ablation, Electrocardiograms were monitored throughout the 1-month p eriod. Results-Eight of the 10 dogs developed complete AV block, 1 dev eloped stable 2:1 AV block, and another had no long-term change in AV nodal conduction. Four dogs attained their maximal degree of AV block in 2 to 5 days. Three of these had no AV nodal conduction changes unti l 2 to 4 days after ablation. Conclusions-An electrosurgical unit can be economically modified for radiofrequency transcatheter ablation, St able, incomplete AV block was rarely induced using this protocol, wher eas complete AV block often developed. A major finding was frequent de lay between energy delivery to the AV nodal region and induction of AV block. Clinical Relevance-Induction of complete AV block using this t echnique, followed by permanent pacemaker placement, is an effective a lternative to long-term antiarrhythmic treatment in animals with chron ic atrial arrhythmias. Transcatheter ablation could be used to treat o ther forms of tachycardia, as it is in human medicine.