Impact of Systemic Vessel Resistance and Microaxial Pump Flow Level on Left Ventricular Workload

The transvalvular microaxial flow pump (mAFP) is increasingly used to unload the failing left ventricle (LV), yet the hemodynamic strategy to maximize unloading remains uncertain. Using a mock circulatory loop with an Impella CP, we tested how systemic vascular resistance (SVR) and pump flow levels influence LV workload. Left ventricle pressure-volume area (PVA) was evaluated across SVR 600-2,000 dyne·s·cm -5 , pump settings P0-P9, and LV contractility (healthy LV, mild, and severe LV dysfunction [LVD]) using two-way analysis of variance (ANOVA) and linear regression. Higher SVR significantly increased PVA, whereas increasing pump setting reduced PVA. However, across all contractility conditions, SVR explained greater than or equal to 4.68-fold more variance in PVA than pump setting (ANOVA sums of squares [×10 6 ]: 171.2-238.7 vs. 8.5-51.0), and regression confirmed a strong association between SVR and PVA ( p < 0.01) while pump setting was not significant ( p = 0.37-0.85). At the highest setting (P9), LV afterload increased, particularly in LVD (mild-severe LVD; p < 0.01), reducing unloading effect and increasing aortic regurgitation. In conclusion, this benchtop mock-loop study suggests lowering SVR may be more effective than escalating mAFP flow to optimize LV unloading, and excessive pump flow may paradoxically impair unloading in LV dysfunction.