Abstract
Left ventricular assist devices (LVADs) have grown in popularity for treating patients with severe heart failure. In many cases rotary blood pumps (RBPs) are used as LVADs, which are set to a fixed rotational speed in the clinical environment. The physicians rely on practical guidelines, available measurements and experience in choosing the rotational pump speed. This can lead to poor or unfavourable patient support, possibly even dangerous operating conditions. Hence, there exists great potential to implement closed-loop control of LVADs to overcome these problems. However, the choice of the control variable is not trivial. This paper presents a methodological approach to deriving a suitable control variable for closed-loop LVAD therapy. To simplify the setpoint choice for clinicians, an assistance ratio is introduced to represent the sharing of hydraulic workload between the LVAD and the native heart. Available measurements include the left ventricular and aortic root pressure, pump flow and aortic flow rate, with the latter estimated using a Kalman filter. Based on these measurements, assistance ratios based on flow, work and pulsatility are proposed. The merits of different assistance ratios are assessed based on their ability to provide insight into hemodynamic support, myocardial protection and left ventricular unloading, along with their ease of implementation and robustness of their calculation. Their implementation is tested in a hybrid mock circulatory loop and retrospectively on data from animal experiments. An assistance ratio based on flow is shown to be the most robust, whilst giving some indication of hemodynamic support. The closed-loop control using an assistance ratio therefore makes it easier to achieve different therapeutic goals. This approach has the potential to reduce interventions by the clinician and could eventually lead to a versatile definition of LVAD therapy protocols, independent of pump-type or patient.
This is a preview of subscription content, log in via an institution to check access.
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
References
P. Ponikowski, A.A. Voors, S.D. Anker, B. Héctor, J.G. Cleland, A.J. Coats, V. Falk, J.R. González-Juanatey, Veli-PekkaHarjola, E.A. Jankowska, et al., European Heart Journal 37(27), 2129 (2016).
H. Frazier, T. Myers, The Annals of Thoracic Surgery 68(2), 734 (1999). https://doi.org/10.1016/s0003-4975(99)00801-2.
G.A. Giridharan, G.M. Pantalos, K.J. Gillars, S.C. Koenig, M. Skliar, ASAIO Journal 50(5), 403 (2004).
R.F. Salamonsen, E. Lim, N. Gaddum, A.H.H. AlOmari, S.D. Gregory, M. Stevens, D.G. Mason, J.F. Fraser, D. Timms, M.K. Karunanithi, N.H. Lovell, Artificial Organs 36(9), 787 (2012). https://doi.org/10.1111/j.1525-1594.2012.01457.x.
A.H.H. AlOmari, A.V. Savkin, M. Stevens, D.G. Mason, D.L. Timms, R.F. Salamonsen, N.H. Lovell, Physiological Measurement 34(1), R1 (2013).
A. Arndt, P. Nüsser, K. Graichen, J. Müller, B. Lampe, Artificial Organs 32(10), 761 (2008). https://doi.org/10.1111/j.1525-1594.2008.00628.x.
D. Rüschen, S. Leonhardt, M. Walter, in 24th Congress of the International Society for Rotary Blood Pumps (ISRBP) (Mito, Japan, 2016).
K.G. Soucy, S.C. Koenig, G.A. Giridharan, M.A. Sobieski, M.S. Slaughter, The Journal of Heart and Lung Transplantation 32(6), 581 (2013).
A. Ündar, B. Ji, B. Lukic, C.M. Zapanta, A.R. Kunselman, J.D. Reibson, W.J. Weiss, G. Rosenberg, J.L. Myers, ASAIO Journal 52(6), 712 (2006).
L.D. Sauren, R.E. Accord, K. Hamzeh, M. De Jong, T. Van Der Nagel, F.H. Van Der Veen, J.G. Maessen, Artificial Organs 31(11), 839 (2007).
B. Misgeld, D. Rüschen, S. Schwandtner, S. Heinke, M. Walter, S. Leonhardt, Biomedical Signal Processing and Control 20, 35 (2015). https://doi.org/10.1016/j.bspc.2015.04.004.
S. Heinke, C. Pereira, S. Leonhardt, M. Walter, Medical & Biological Engineering & Computing 53(10), 1049 (2015).
D. Rüschen, M. Rimke, J. Gesenhues, S. Leonhardt, M. Walter, Computer Methods and Programs in Biomedicine (2016). https://doi.org/10.1016/j.cmpb.2016.08.020. [Epub aop].
Acknowledgements
In the ongoing in vivo study, all national and European laws, guidelines and policies for the care and use of laboratory animals are followed. This work has been funded by the Federal Ministry of Education and Research (BMBF, Germany) and is part of the project “inHeart” (grant number 13GW0118C).
Author information
Authors and Affiliations
Corresponding author
Editor information
Editors and Affiliations
Ethics declarations
The authors declare that they have no conflict of interest.
Rights and permissions
Copyright information
© 2019 Springer Nature Singapore Pte Ltd.
About this paper
Cite this paper
von Platen, P., Rüschen, D., Leonhardt, S., Walter, M. (2019). Assistance Ratio: An Approach to Quantify the Hydraulic Load Distribution in LVAD Therapy. In: Lhotska, L., Sukupova, L., Lacković, I., Ibbott, G.S. (eds) World Congress on Medical Physics and Biomedical Engineering 2018. IFMBE Proceedings, vol 68/1. Springer, Singapore. https://doi.org/10.1007/978-981-10-9035-6_137
Download citation
DOI: https://doi.org/10.1007/978-981-10-9035-6_137
Published:
Publisher Name: Springer, Singapore
Print ISBN: 978-981-10-9034-9
Online ISBN: 978-981-10-9035-6
eBook Packages: EngineeringEngineering (R0)