Abstract 19747: The Effect of Internal vs. External Shocks on Myocardial Injury in an Animal Model of Myocardial Infarction
Introduction: ICD use early after myocardial infarction (MI) has not proven advantageous, possibly in part due to myocardial injury associated with intracardiac defibrillation shocks. Previous studies have reported myocardial injury with internal defibrillation, but external defibrillation from the wearable cardioverter defibrillator (WCD) has not been investigated. The goal of this study was to determine the acute damage to the heart caused by external defibrillation from the WCD as compared to an ICD in an animal model of myocardial infarction (MI) using typical energy levels and times to shock.
Methods: Two weeks after MI creation, 20 pigs were anesthetized and induced into VF through direct current applied to the right ventricular endocardium via an implanted transvenous lead. Control animals received 20-J internal shocks from the dual-coil defibrillator lead after 30 seconds of VF, while experimental animals received 150-J external shocks from a WCD after 45 seconds of VF. Each animal received a total of five consecutive internal or external shocks. Blood samples were collected at baseline (prior to first shock), immediately after the last shock, and at 4- and 24-hours post-shocks to determine myocardial biomarkers. Animals that did not survive 24 hours, control animals that had to be rescue-defibrillated externally, or those requiring >5 shocks were excluded from analysis (n=6, 3 per arm). Differences were determined using t-tests.
Results: Troponin I (cTnI), a specific marker of myocardial damage, was elevated above baseline in both the ICD (n = 7) and WCD (n = 7) groups at the 4 hr and 24 hr post-shock time points (Figure). However, the cTnI at 4 hr and 24 hr was significantly higher in the ICD control group as compared to the WCD (p < 0.05).
Conclusions: In an animal model of myocardial injury, cardiac-specific cTnI increases are significantly greater following internal 20-J shocks than external 150-J shocks, indicating less myocardial damage with external shocks.
- Ventricular Defibrillation
- Myocardial Infarction
- Ventricular Fibrillation
- Implantable cardiovertor defibrillator
Author Disclosures: N.R. Bianco: Employment; Significant; ZOLL. R. Perumal: Employment; Significant; ZOLL. S.J. Szymkiewicz: Employment; Significant; ZOLL.
- © 2015 by American Heart Association, Inc.