Abstract 85: Development of a Readily Translatable Model of Resuscitation From Ischemic Cardiac Arrest to Assess Regional and Global Arrhythmia Substrates and Outcomes
Background: Little is known about the effect of therapeutic hypothermia (TH) on arrhythmias in the resuscitated heart. TH has a beneficial effect on defibrillation thresholds and ROSC. However, there are no studies investigating why TH might be anti-arrhythmic during resuscitation from ischemia-induced cardiac arrest, the most common clinical scenario. Our goal was to develop a novel translational porcine model of resuscitation from regional ischemia-induced VF with the ability to identify differences in both regional and global arrhythmia substrates in order to determine mechanisms of the antiarrhythmic effect of TH and improve outcomes.
Methods: Pigs underwent anesthesia and thoracotomy, and a large LAD occlusion was made. VF was induced after 30 min if spontaneous VF did not occur. CPR was started after 8 min with defibrillation and cardiac massage to achieve ROSC. Infarct was continued for a total of 60 min then reperfusion was continued for 60 min. Electrograms (EG) were recorded from multipolar needle (transmural) plunge electrodes at multiple sites and monophasic action potential (MAP) recordings were used to determine transmural and regional heterogeneities of repolarization and conduction. All spontaneous arrhythmias were recorded. Outcomes were compared between control (temp 37oC, CT), Pre-ischemia TH (TH 33oC), and post-infarct TH (TH-infarct). Cooling was induced using a cooling blanket, cold saline IV infusion, and ice packs.
Results: Hemodynamic parameters were recorded during ischemia, during CPR, and reperfusion. Appropriate CPR was verified by BP and CO2 monitoring. 2/4 animals survived to the end of protocol in the CT group, 4/5 in the TH group, and 0/2 in the TH-infarct group. Total ROSC time was 9.8±7 for CT vs 37.5±6 (p<.04) for TH group (no ROSC for TH-infarct). EG’s were used to assess activation recovery intervals at transmural sites in the infarct, noninfarct, and border zones. Regional VF waveforms were obtained.
Conclusions: We developed a translatable model of resuscitation from ischemic cardiac arrest using regional and global electrophysiologic monitoring to assess arrhythmia substrates. These data suggest improved outcomes during resuscitation with TH.
- © 2013 by American Heart Association, Inc.