Improving left ventricular unloading following prolonged cardiac arrest using a minimally invasive left ventricular assist device: a prospective animal study in pigs

Cardiopulmonary resuscitation (CPR) is an emergency procedure deployed when a patient suffers cardiac arrest (CA). Compared to conventional CPR, improved survival is observed after CA when CPR is conducted in the presence of a minimally invasive left ventricular assist device, Impella 2.5 (iCPR). However, data on myocardial function during and following iCPR are lacking. To assess cardiac functional parameters during and following iCPR. Five 55.2±2.4 kg pigs were anesthetized, intubated, and implanted with an Impella 2.5. Ventricular fibrillation (VF) was electrically induced and left untreated for 9 minutes before defibrillation was attempted following six minutes of iCPR. During iCPR, the Impella device was set to the maximally achievable flow. 1hr following return of spontaneous circulation (ROSC), mild therapeutic hypothermia was induced for 16 h using a total of 4 liters of 6° C cold saline infusions and ice bags. To assess myocardial recovery, we used 2-D echocardiography, tissue Doppler (TDI), and Speckle-tracking. All animals received transesophageal echocardiography at baseline, during untreated cardiac arrest, at the initiation of iCPR, 30 minutes, and 5 hours following ROSC. Left ventricular (LV) systolic parameters returned to baseline values 5 h after ROSC (global longitudinal strain: -25±4.3% vs. -20±2.7%; p=0.388; EF(%): 64±8.8 vs. 61.32±10.3, p=0.971; stroke volume index (mL/m2): 28.32±8.9 vs. 24.71±12.86, p=0.545). LV volume unloading was also observed over the same time period. LV end-diastolic volume was 55.38±2.8 mL at baseline, peaked after CA at 64.7±9.9 mL, fell to 45.69±7.4 mL 30 min after initiation of iPCR, and was maintained at 49.46±13.9 mL 5 h after ROSC. Recovery of the RV systolic parameters was not observed during the first 5 h following ROSC (baseline vs. 5hr after ROSC: TDI derived TASV (cm/s): 11.6±1 vs. 8.5±1, p=0.005, RV- FAC (%): 42±6.2 vs. 33±6.9, p=0.006). iCPR is able to achieve a full recovery of LV systolic parameters and provides sufficient LV volume unloading. The observed RV distension is likely attributable to extensive volume loading. Further studies are needed to analyze long term LV and RV function following CA and iCPR support