Circulation, Vol 80, 951-961, Copyright © 1989 by American Heart Association
SK Huang, S Bharati, AR Graham, G Gorman and M Lev
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 (greater than 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 (greater than
50%) or persistent second-degree AV block (lasting greater than 30 minutes)
after ablation, 2) occurrence of two consecutive transient (less than 1
minute) complete AV blocks after each energy delivery, or 3) complete AV
block (lasting greater than 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.
ARTICLES
Chronic incomplete atrioventricular block induced by radiofrequency catheter ablation
Department of Internal Medicine, Tucson Veterans Administration Medical Center, Arizona.
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