Evaluation of Left Ventricular Relaxation in Rotary Blood Pump Recipients Using the Pump Flow Waveform: A Simulation Study

Abstract

In heart failure, diastolic dysfunction is responsible for about 50% of the cases, with higher prevalence in women and elderly persons and contributing similarly to mortality as systolic dysfunction. Whereas the cardiac systolic diagnostics in ventricular assist device patients from pump parameters have been investigated by several groups, the diastolic behavior has been barely discussed. This study focuses on the determination of ventricular relaxation during early diastole in rotary blood pump (RBP) recipients. In conventional cardiology, relaxation is usually evaluated by the minimum rate and the time constant of left ventricular pressure decrease, dP/dt(min) and τ(P) . Two new analogous indices derived from the pump flow waveform were investigated in this study: the minimum rate and the time constant of pump flow decrease, dQ/dt(min) and τ(Q) . The correspondence between the indices was investigated in a numerical simulation of the assisted circulation for different ventricular relaxation states (τ(P) ranging from 24 to 68 ms) and two RBP models characterized by linear and nonlinear pressure-flow characteristics. dQ/dt(min) and τ(Q) always correlated with the dP/dt(min) and τ(P) , respectively (r>0.97). These relationships were influenced by the nonlinear pump characteristics during partial support and by the pump speed during full support. To minimize these influences, simulation results suggest the evaluation of dQ/dt(min) and τ(Q) at a pump speed that corresponds to the borderline between partial and full support. In conclusion, at least in simulation, relaxation can be derived from pump data. This noninvasively accessible information could contribute to a continuous estimation of the remaining cardiac function and its eventual recovery.

Hemodynamic exercise responses with a continuous-flow left ventricular assist device: Comparison of patients’ response and cardiorespiratory simulations

“…However, a proper characterization of patient residual adaptation mechanisms to exercise is important for the design of exerciseresponsive LVADs. High-resolution LVAD flow waveforms have proven to be a valuable source of information for the detection of patient's hemodynamic status [5]: Aortic valve (AV) opening [6,7], heartrate [8], suction events [9], contractility and relaxation parameters [10,11]. This LVAD-based diagnostics can be therefore performed systematically during exercise tests, thus revealing the unobserved information of this complex interaction between heart and LVAD.…”

Artificial Organs 2012: A Year in Review

“…Francesco Moscato et al. of the Medical University of Vienna, Vienna, Austria reported on the determination of ventricular relaxation during early diastole in rotary blood pump recipients. Two new analogous indices derived from the pump flow waveform were investigated in a numerical simulation study: the minimum rate and the time constant of pump flow decrease, dQ/dt(min) and τ(Q).…”

Development of pressure estimation for external rotary blood pump

“…The meaning of each parameters compose of AoP (t) represented aortic pressure, LVP(t) represented the left ventricular pressure, Q(t) represented the pump flow, ω represented the pump rotational speed, B represented a constant speed related coefficient, R p represented the constant slope of the linear pressure-flow characteristics, and L p represented the constant fluid inertance [6]. This proposed model identified the value of each parameter as a constant value.…”