Abstract 17961: Endocardial Defibrillation is Associated with Transient Wall Motion Abnormalities and Significant Pathology Findings in the Domestic Pig
Introduction: Implantable cardioverter defibrillators (ICD) improve overall survival in systolic heart failure human patients. However, ICD therapy by means of defibrillation is associated with a slightly higher mortality risk (for appropriate and inappropriate therapies). With the aim to define objective wall motion and histological changes associated with defibrillation and create a working model for future research and to determine parameters for safe defibrillation, we conducted the following study.
Methods: To isolate the effects of defibrillation, five healthy domestic pigs (Sus scrofa) with average weight 155 lbs successfully received an ICD system, with pulse generator implanted in the left suprathoracic area and a 7Fr. dual coil right ventricular endocardial lead. Testing was conducted in sinus rhythm and under general anesthesia. With a B->AX vector, two subjects got one ”single” 35 J biphasic shock, two got ten 35 J biphasic shocks (“storm”) as fast as the capacitors were able to charge and deliver therapy and one subject was used as control. The subjects underwent transthoracic echocardiography to assess wall motion before, after and one week later prior to euthanasia. An autopsy was performed at that time.
Results: Septal wall motion abnormalities were noted in all subjects after defibrillation with complete resolution within 15 minutes. Autopsy showed no macroscopic changes one week after testing. The right ventricles that received therapy showed multiple islands of hypereosinophilic and vacuolated degenerate myofibers that were transmural and adjacent to each other. Left ventricles showed some scattered hypereosinophillic degenerate myofibers. Control subject showed rare hypereosinophillic degenerate myofibers.
Conclusions: Endocardial defibrillation is associated with reversible short term post therapy delivery changes in local wall motion and significant histopathological changes related to scarring and degeneration in both ventricles one week after therapy delivery in the domestic pig. Further studies are needed to assess the potential relationship of these findings with clinical outcomes and to determine thresholds for myocardial damage.
- © 2011 by American Heart Association, Inc.