Automated Impella Controller overestimates device flow: direct measurement in a mock circulatory loop

Impella CP and 5.5 devices are widely utilized, yet their flow characteristics have not been independently verified. DanGer Shock demonstrated mortality benefit with Impella CP in cardiogenic shock, 6-month mortality remained 45.8%.1 Better understanding of device flow may improve clinical decision-making. The Automated Impella Controller (AIC) uses motor parameters and proprietary algorithms to derive flow estimates. Experience with durable ventricular support devices has demonstrated that console flow estimates may be inaccurate.2 We compared AIC flow to direct flow measurement and to determine console accuracy. We tested Impella CP and 5.5 in a validated mock circulatory loop incorporating vascular resistance, compliance chambers, and bioprosthetic cardiac valves (Figure 1).3 Devices were inserted per manufacturer guidelines. Instantaneous flow was measured using calibrated ultrasound clamp-on sensors positioned distal to the device outlet, with peri-device flow occluded ensuring only intra-device flow was recorded. The pulsatile circuit incorporated a Y-configuration distal to the aortic valve: One limb contained the Impella with peri-device occlusion, ensuring exclusive device flow measurement; the second limb serves as a bypass conduit for native left ventricular ejection. Pressure differential between the left ventricle and aorta was recorded using Millar catheters. The head-flow (HQ) relationship describing how pressure differential affects device flow was determined. A 40% aqueous-glycerol solution was circulated at temperatures corresponding to haematocrits of 33–41%.4 For each Performance-level (P1-P9), systemic resistance was varied to create different pressure heads. Recordings were performed at 100 Hz for 30 s under non-pulsatile and pulsatile (60 bpm) conditions where flow through the aortic valve was visually confirmed. Data were analysed with paired t-tests comparing AIC-reported and directly measured flow within each experimental condition.