Circulation, Vol 64, 242-245, Copyright © 1981 by American Heart Association
GM Deeb, BP Griffith, ME Thompson, A Langer, MS Heilman and RL Hardesty
We examined the feasibility of using a standby automatic implantable
defibrillator and established thresholds for internal defibrillation. The
implantable defibrillator senses ventricular fibrillation and delivers an
electrical impulse for defibrillation. Two lead systems for the device have
been investigated. System I consists of two 12-cm2 silicone-covered
titanium mesh patches attached to the atrial and diaphragmatic pericardial
surfaces. System II has an identical diaphragmatic patch and a titanium
spring catheter, with a 12-cm2 surface area of conductivity, placed
transvenously in the right atrium. Both systems were implanted by
thoracotomy in 12 dogs (mean weight 20 kg) and by a subxiphoid approach in
10 pigs (mean weight 20 kg). The defibrillation threshold (lowest energy
required for 80% success) was determined periodically for 54 weeks in the
dogs (615 trials) and at 6 weeks for the pigs (100 trials). In dogs, the
mean defibrillation threshold with system I leads at 4 weeks was 10.5 J and
did not change significantly over a 54-week period (p greater than 0.05).
Similar results were obtained in the pig at 4 weeks. The defibrillation
thresholds for both lead systems in dogs and pigs using a transpleural
thoracotomy or a subxiphoid approach are satisfactory for an implantable
defibrillator that produces 20-35 J.
ARTICLES
Lead systems for internal ventricular fibrillation
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