Abstract 330: Intra-Arrest Cardioplegia Prevents the Diastolic Dysfunction Induced by Prolonged VF Arrest

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Introduction: There are approximately 400,000 out-of-hospital cardiac arrests annually, including one-third with VT/VF as their initial rhythm. Approximately 60% of VF arrests are refractory to initial resuscitation requiring prolonged CPR and transport to an ECPR center where available. Limiting myocardial injury during this time is critical as it contributes CPR efficiency. The aim of this study was to investigate the effect of cardioplegia on preservation of cardiac function during cardiac arrest. Hypothesis: Following induction of VF, the administration of potassium-based cardioplegia will reduce energy utilization and prevent diastolic dysfunction with preservation of contractility following washout of cardioplegia. Methods: Hearts were isolated from male Brown Norway rats (n=8) and prepared on a Langendorff apparatus in Krebs solution. Left ventricular pressure was measured throughout the study. Hemodynamics were obtained for 15 min prior to 2 min of rapid pacing to induce VF. After 10 min of VF, cardioplegia was induced with a bolus of 160 μeq potassium. After 10 min, the potassium was washed out and the hearts were reperfused with Krebs-Henseleit solution. Hemodynamics were measured for another 60 min. Results: Baseline hemodynamics were similar between the control and cardioplegia groups. Cardioplegic hearts had significantly lower left heart pressures at the end of the VF time compared to control hearts (24 vs. 74 mmHg, p<0.05). Following 60 min of reperfusion and cardioplegia washout, diastolic pressures remained lower in hearts receiving cardioplegia (39 vs 10 mmHg, p<0.05). After 60 min of reperfusion, systolic pressures were the same among the groups, and while rate of contraction and relaxation were numerically faster in hearts receiving cardioplegia, these differences were not significant. Conclusions: Potassium cardioplegia, given during ongoing VF arrest, was effective at preventing diastolic dysfunction caused by prolonged ischemia. Washout of the cardioplegia at the time of reperfusion allowed for ROSC and preserved left ventricular relaxation. These studies suggest that the use of cardioplegia in refractory VT/VF arrest may be beneficial in reducing myocardial damage and preserving function during prolonged CPR.