Endocavitary ablation of atrioventricular conduction

Mapping guided laser catheter ablation of the atrioventricular conduction in dogs

Safety and efficacy of mapping guided laser catheter ablation of the AV junction was tested in a canine model. A total of 43 laser pulses (continuous wave, Nd:YAG, 1,064 nm, 30 W, irradiated spot diameter 2.0-2.5 mm) were delivered in 15 dogs (2-5 per dog) via a novel laser catheter system. Pulses were selectively aimed at: (1) the AV node; (2) the His bundle; and (3) the bundle branches. Laser pulses of 9.7 +/- 1.1 seconds (n = 31) produced reversible conduction disturbances in the targeted segment of the AV conduction system, while pulses of 28.6 +/- 7.9 seconds (n = 9) resulted in chronic block. The dogs survived the procedure without complications. Follow-up was 6.5-10.5 months. Histopathologically, lesions showed clear-cut oval-shaped areas of fibrosis of 0.5-18.0 mm in diameter and 0.5-3.5 mm (transmural) in depth, depending on the irradiation time. Pervenous mapping guided laser catheter irradiation of the AV junction can produce AV block consistently and selectively in the targeted segment of the right ventricular conduction system in dogs. The method is safe and can be performed in a controllable manner by using the catheter system presented.

Bipolar transseptal radiofrequency ablation of AV node: an alternative to high energy shocks?

Atrioventricular (AV) node ablation to control ventricular response was attempted in two patients with recurrent drug refractory atrial flutter. Standard radiofrequency (RF) procedure, which delivers energy through the 4-mm tip electrode of an ablation catheter positioned at the right AV junction and a large back plate (unipolar mode), failed in both patients. As an accepted second step, high energy direct current (DC) ablation under general anesthesia was then performed in patient one. After two shocks of 200 J, complete AV block occurred, but complete recovery was noted 3 hours later. In a third session for patient 1 and in the first session for patient 2 (after 15 unsuccessful unipolar right-sided RF applications), a second ablation catheter was introduced via the femoral artery on the left side of the His bundle area under the aortic valves. Energy was then delivered in a bipolar fashion between the tip electrodes of the right-sided and the left-sided catheter. Complete and permanent AV block (follow-up: 3 and 1 months) was created within 4 and 1.5 seconds, respectively, in each patient. No complication was encountered and echocardiograms and blood levels of cardiac enzymes were all normal after the procedures. This new approach, after further evaluation, may represent a useful additional step in the strategy of AV node ablation and could be applied before high energy DC shock when the standard RF procedure is unsuccessful.