The Influence of Mock Circulation Input Impedance on Valve Acceleration During In Vitro Cardiac Device Testing

Abstract

For a mechanical heart valve, a strong spike in pressure during closing is associated with valve wear and erythrocyte damage; thus, for valid in vitro testing, the mock circulation system should replicate the conditions, including pressure spikes, expected in vivo. To address this issue, a study was performed to investigate how mock circulation input impedance affects valve closure dynamics. A left ventricular model with polyurethane trileaflet inflow valve and tilting disc outflow valve was connected to a Louisville mock circulation system, which incorporates 2 adjustable flow resistors and 2 compliances. In the study, 116 cases matched zero frequency modulus well (982-1147 dyn x s/cm), but higher harmonics were purposely varied. Acceleration measured at the outflow valve ring (42.4-89.4 milli-Gs) was uncorrelated with impedance error (74.1-237 dyn x s/cm relative to target impedance), but was correlated with end-systolic impedance (1082-1319 dyn x s/cm) for cases with high zero frequency modulus, which exhibited just less than full ejection. These differences demonstrate that mock circulation response affects the magnitude of the closing spike, indicating that control of this parameter is necessary for authentic testing of valves. Correlation of acceleration to end-systolic impedance was weak for low zero frequency modulus, which tended toward full or hyperejection, reinforcing common laboratory observations that valve closing also depends on ventricular operating conditions.

Numerical and In Vitro Investigation of a Novel Mechanical Circulatory Support Device Installed in the Descending Aorta

“…It is evident that at the LVP of 100 mm Hg, a significant oscillation is appearing on the experimental trace. This is regarded as the hammer effect which is due to the sudden closure of the rigid leaflets of the mechanical valve .…”

In Vitro Cardiovascular System Emulator (Bioreactor) for the Simulation of Normal and Diseased Conditions With and Without Mechanical Circulatory Support

“…describes a twin‐chamber SCVL to investigate the effect of opening and closing of the aortic valve on hemodynamic response to the continuous flow produced by a left‐side VAD. Another work describes a twin‐chamber SCVL to study the effect of arterial impedance on the closing dynamics of prosthetic heart valves. These devices have good ability to replicate the action of the native system at physiological and pathological conditions, but have inherent limitations in emulating atrium‐to‐ventricle and ventricle‐to‐artery interactions of both systemic and pulmonary circulations.…”

Left Atrial Appendage Occlusion: Current Stroke Prevention Strategies and a Shift Toward Data-Driven, Patient-Specific Approaches

“…Bench-top circulatory flow loops are designed to simulate the cardiovascular hemodynamics of physiologic systems. To accurately model the human cardiovascular environment without relying on prohibitively expensive and time-consuming in vivo, large-animal studies, 3 main experimental approaches have been described: the use of synthetic ventricles, [118][119][120] the integration of passive excised biological samples into artificial in vitro setups, [121][122][123][124][125] and the use of ex vivo beating heart models. [126][127][128] Synthetic models allow for easily controlled and repeatable experimental conditions but fail to recapitulate the complex Ex vivo beating heart models provide highly realistic cardiac physiology.…”