Estimation of left ventricular pressure with the pump as "sensor" in patients with a continuous flow LVAD.
BACKGROUND
In long-term ventricular support of patients with LVADs, left ventricular pressure (p(lv)) is relevant for indicating the unloading level of the heart. Monitoring of p(lv) over time might give more insight into the increase or decrease in native ventricular function. In this study, we aim to assess dynamic p(lv) noninvasively, using the LVAD as a pressure sensor.


METHODS
Pressure head (dp(lvad)) was estimated from pump flow with a dynamic pump model (1). Estimated dp(lvad) and measured aortic pressure were used to calculate left ventricular pressure. Moreover, parameters dp/dtmax and mean, minimum, and maximum p(lv) were derived.The method was validated with a porcine ex vivo beating heart model by measurements conducted in 4 hearts supported with a Micromed DeBakey VAD and 3 hearts with a Heartmate II VAD. During each measurement, aortic and left ventricular pressure, pump flow, and pressure head were recorded for 30 s with a sampling frequency of 1 kHz.


RESULTS
The estimation of left ventricular pressure appeared to be accurate for both pumps. The parameters mean and minimum pressure were estimated with high accuracy. The degree of accuracy of the estimated p(lv) was proportional to the degree of accuracy of the dynamic pump model.


CONCLUSIONS
We proved that the LVAD model described in this paper can be used as a pressure indicator to determine LV pressure at any time based on noninvasive measurements of pump flow, aortic pressure, and the properties of the outlet graft.
Department of Cardio-thoracic Surgery, Academic Medical Center, Amsterdam - The Netherlands.|Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven - The Netherlands.
Kim A M A
KA
Pennings
LifeTec Group B.V., Eindhoven - The Netherlands.
Sjoerd
S
van Tuijl
Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven - The Netherlands.
Frans N
FN
van de Vosse
Department of Cardio-thoracic Surgery, Academic Medical Center, Amsterdam - The Netherlands.
Bas A J
BA
de Mol
Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven - The Netherlands.
Marcel C M
MC
Rutten
D000818:Animals; D001783:Blood Flow Velocity / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology*; D006353:Heart-Assist Devices; D023421:Models, Animal; D008955:Models, Cardiovascular; D013552:Swine; D016277:Ventricular Function, Left / Q000502:physiology*