Abstract Body (Do not enter title and authors here): Introduction: The combination therapy of venoarterial extracorporeal membrane oxygenation (VA-ECMO) and transaortic valve micro-axial flow pump catheter (Impella), so-called ECPELLA, provides powerful hemodynamic support and left ventricular (LV) unloading for cardiogenic shock (CS). However, aortic insufficiency (AI) caused by Impella placement reduces those benefits of ECPELLA.
Research Questions: This study investigated the impact of Impella-induced AI on the effects of hemodynamic support and LV unloading by ECPELLA. We examined the relationship between AI severity and regurgitant flow (AI flow) using mock circulation and confirmed the presence of AI-induced hemodynamic deficit in a goat model of ECPELLA. Furthermore, we evaluated the impact of varying AI severity on hemodynamics and LV pressure-volume (PV) loop in ECPELLA circulation by our developed cardiovascular simulation.
Methods: In a closed mock circuit with a centrifugal pump, we evaluated the relationship between the AI severity, which was altered by the position of the Impella at the aortic valve (Fig. 1A), and the effective regurgitant orifice area (EROA) estimated from AI flow and pressure gradient. Five Saanen goats (53±2 kg) were used for animal experiments of ECPELLA (Fig. 1B). VA-ECMO flow was set at 1.0, 1.5, and 2.0 L/min. AI flow was calculated from the difference between pulmonary artery and Impella flows. We developed a cardiovascular simulation that employed four cardiac chambers with resistance-compliance networks incorporating ECPELLA (Fig. 1C). Using four AI severity levels, we calculated the hemodynamics and illustrated PV loops by changing Impella CP settings from P0 to P9 under VA-ECMO support.
Results: In mock circulation, AI flow increased according to the pressure gradient in each AI severity. Estimated EROA values were 0.018, 0.056, and 0.75 cm² for minimal, mild, and severe AI, respectively (Fig. 2A). In goats with ECPELLA, we observed the presence of AI with EROA of 0.18 cm² (Fig. 2B). In the simulation, the higher AI severity markedly attenuated the Impella impact on hemodynamic improvement and the leftward and downward shift in PV loop (Fig. 2C).
Conclusion: Inappropriate Impella position can cause severe AI. Severe AI substantially reduces both hemodynamic support and LV unloading effects of ECPELLA. Systematic AI assessment is critical for optimal ECPELLA management in CS patients.