Lead systems for internal XXXX .

@entity1707 @entity235 @entity737 @entity1346 @entity2224 @entity702
We examined the feasibility of using a standby @entity737 and established thresholds for internal defibrillation. The implantable defibrillator senses @entity2224 and delivers an electrical impulse for defibrillation. Two lead systems for the device have been investigated. System I consists of two 12-cm2 @entity1346 -covered @entity702 mesh patches attached to the atrial and diaphragmatic pericardial surfaces. System II has an identical diaphragmatic patch and a @entity702 spring catheter, with a 12-cm2 surface area of conductivity, placed transvenously in the right atrium. Both systems were implanted by thoracotomy in 12 @entity235 (mean weight 20 kg) and by a subxiphoid approach in 10 @entity1707 (mean weight 20 kg). The defibrillation threshold (lowest energy required for 80% success) was determined periodically for 54 weeks in the @entity235 (615 trials) and at 6 weeks for the @entity1707 (100 trials). In @entity235 , 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 @entity1707 at 4 weeks. The defibrillation thresholds for both lead systems in @entity235 and @entity1707 using a transpleural thoracotomy or a subxiphoid approach are satisfactory for an implantable defibrillator that produces 20-35 J.
