Chronic incomplete atrioventricular block induced by radiofrequency catheter ablation.

Abstract

To determine if catheter ablation of the atrioventricular (AV) junction with radiofrequency energy can induce chronic incomplete (first-and second-degree) AV block to avoid the need for a permanent pacemaker, 20 closed-chest dogs were studied. Group 1 (10 dogs) received radiofrequency energy (750 kHz) with a fixed power setting (5 or 10 W) while increasing the pulse duration from 10 to 50 seconds for each application. Group 2 (10 dogs) received energy with a fixed pulse duration (20 or 30 seconds) while increasing the power setting from 5 to 10 W or from 10 to 20 W during each energy delivery. Radiofrequency energy was delivered between a chest-patch electrode and the distal electrode of a regular 7F tripolar His bundle catheter. For each application, the energy delivery was interrupted when 1) the PR interval prolonged (>50%) or 2) second-degree or complete AV block occurred and persisted up to 5 seconds. The ablation procedure ended when there was 1) persistent PR prolongation (>50%) or persistent second-degree AV block (lasting >30 minutes) after ablation, 2) occurrence of two consecutive transient (<1 minute) complete AV blocks after each energy delivery, or 3) complete AV block (lasting >2 minutes) after ablation. Of seven dogs in group 1 and five dogs in group 2 in which incomplete AV block was achieved 1 hour after the procedure, six in group 1 and five in group 2 remained in incomplete AV block 2-3 months after ablation. One dog in group 1 progressed into complete AV block. Of the remaining three dogs in group 1 and five dogs in group 2 in which complete AV block was initially achieved 1 hour after ablation, two in group 1 and four in group 2 continued to have complete AV block, whereas one in each group had AV conduction returned to incomplete at 1-2 months of follow-up. Thus, a total of 13 dogs had chronic incomplete AV block induced by radiofrequency catheter ablation. Pathologic examination of the conduction system in two dogs with first-degree AV block, two dogs with second-degree AV block, and one dog with complete AV block showed discrete scars involving the approaches to the AV node and the AV node itself. It is concluded that, in most dogs studied, chronic incomplete AV block could be achieved by careful titration of the dosage of radiofrequency energy and by regulation of the ablation end points. (Circulation 1989;80:951-961) Catheter ablation of the atrioventricular (AV) junction with direct-current electrical energy has been performed in animalsl2

Experimental, Pathologic, and Clinical Findings of Radiofrequency Catheter Ablation of Para-Hisian Region From the Right Ventricle in Dogs and Humans

“…10,11 In the 7 dogs from group 1, radiofrequency-induced coagulative necrosis of the PHB resulted in total AV block in 3 dogs and HV prolongation in 1 dog. On the other contrary, no lesion in PHB in 3 dogs can be explained by (1) radiofrequency lesion depth with a limited energy of 25 W and 60 seconds might have created the lesion depth not enough to penetrate the PHB encased in the central fibrous body and (2) the range of bipolar recording and pacing may be too large, which may differ from unipolar pacing.…”

Impact of Transforming Growth Factor-β1 on Atrioventricular Node Conduction Modification by Injected Autologous Fibroblasts in the Canine Heart

“…41,42 The data and techniques provided here are in contrast to other methods attempted to focally modify the AV node that have resulted in unacceptably high rates of high-grade block. [11][12][13][14][15][16][17] These studies used radiofrequency ablation techniques. Despite focal delivery of energy, untoward injury to distant and collateral tissues and organs remains a common problem.…”

“…9,10 Partial alteration of AV nodal conduction with radiofrequency ablation to avoid pacemaker implantation has resulted in improvement in ventricular rate control, although highgrade AV block is a frequent complication. [11][12][13][14][15][16][17] These limitations provide the incentive for the development of new treatment strategies. One such approach would be to use cell therapy to interrupt or to modify conduction into the AV node.…”