Abstract 1663: Safety of High-Energy (70-Joule) Non-Transvenous Defibrillation Shocks
Background: A non-transvenous ICD offers potential advantages over a transvenous ICD including simplification of the implant procedure and reduced acute and chronic morbidity and mortality associated with the transvenous lead. However, such a system will need a higher energy to achieve defibrillation efficacy comparable to transvenous systems. The effect of higher energy non-transvenous shocks on tissues within the shock field has not been previously characterized or compared to transvenous shocks.
Methods: Eight swine (69±2kg) were implanted with a 25-cm subcutaneous defibrillation coil on the left posterior thorax and a Can electrode in the left pectoral region. Of these, 4 control subjects received a defibrillation lead in the RV apex and 4 test subjects received a pacing lead in the RV apex. Control subjects received five, 35-J shocks between RV coil and Can; test subjects received five, 70-J shocks between subcutaneous coil and Can. Shock response was assessed through analysis of 12-lead ECG, LV and arterial BP immediately before, after, and 10 min. following all shocks. Measurements of Troponin I in blood at pre-shock, 4 hr and 24 hr post shock were made to assess cardiac injury. A gross and histopathologic examination of cardiac and pulmonary tissues was made 24 hours following shocks.
Results: ECG and BP records revealed no differences between groups at points immediately after shock and 10 minutes after shock delivery. Troponin I levels were greater in the control group at the 4 hr and 24 hr time points (Table⇓). Pathologic examination of cardiac and pulmonary tissues within the shock field revealed test group findings were no more severe than control group.
Conclusions: Non-transvenous anteroposterior 70-J shocks are not associated with increased cardiac or lung injury as compared to 35-J transvenous shocks. The results suggest that in terms of acute myocardial injury, despite higher energy, the non-transvenous shocks may be more benign than transvenous shocks.