Detection of physiological control inputs preload and afterload from intrinsic pump parameters in total artificial heart

Abstract

Background In the total artificial heart (TAH), the inputs to the physiological control unit, preload, and afterload, are detected from intrinsic pump parameters (e.g., motor current). Within this study, their detection techniques are developed, and their reliability in pre‐ and afterload prediction is mapped for a broad range of cardiovascular system states. Methods We used ReinHeart TAH which is a fully implantable TAH with a plunger coil drive that is alternately emptying the left and right chambers. From the coil currents we first derived a force generated by the piston with respect to its position and then analyzed its pattern to detect (1) preload—chamber filling, found as piston position at begin ejection and (2) afterload—mean outflow pressures, determined as linearly calibrated average piston force during ejection. TAH is then integrated into a mock loop circulation (MLC) which is set to 135 different steady operating points varying in chamber filling (0%–100%, five steps), mean outflow pressures (system circulation: 60–90–120 mm Hg, pulmonary circulation: 15–30‐45 mm Hg), and heart cycle duration (171–600 ms in seven non‐equidistant steps). The detected preload and afterload are compared to MLC set values, and the errors are mapped. Results Respectively for the left and right chambers, the preload was detectable in 134 and 118 operating points and the mean error was ±3% and ±2%. The afterload was detectable in 135 and 87 operating points and the mean error was 37% and 30% respectively for left and right circulation. The operational points that are further away from homeostatic equilibrium values generally yielded larger errors. The largest errors were observed for right circulation at long cycle duration, low afterload, and low filling. Conclusions The study yields reliable preload estimation in a broad range of physiological states, particularly for left circulation. Detection of afterload needs further improvements. The study revealed a need for piston movement optimization within the ReinHeart TAH during the early phase of systole.

Design and preparation of an artificial vascular scaffold with internal surface modification

“…The heartbeat of the heart included diastole and systole, and each contraction and relaxation of the heart constitutes a cardiac cycle, so the blood flow rate would also produce periodic changes 25,26 . According to the Doppler blood flow waveforms in IVC reported by Zhang et al., 27 the fastest flow velocity of 0.5 m/s and the slowest flow velocity of 0.1 m/s in inferior vena cava were selected for simulation.…”

“…The cylindrical hydrogel samples were placed on the disk platform where ∞ = 3.5 × 10 −3 kg/(m s), 0 = 5.6 × 10 −2 kg/(m s), n = 0.3568, and = 3.313 s. 24 The heartbeat of the heart included diastole and systole, and each contraction and relaxation of the heart constitutes a cardiac cycle, so the blood flow rate would also produce periodic changes. 25,26 According to the Doppler blood flow waveforms in IVC reported by Zhang et al, 27 the fastest flow velocity of 0.5 m/s and the slowest flow velocity of 0.1 m/s in inferior vena cava were selected for simulation. The velocity of the vascular scaffold cross section and the pressure, velocity, and direction of blood flow in the S1-S7 section were monitored, and the data were analyzed.…”