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A Physiological, Pulsatile Driver for Continuous Flow Left Ventricular Assist Device (LVAD): Innovation Using an Implantable Ultra-compact Microcontroller with a Wireless Graphical User Interface.
Asgari, Sam1, Bonde, Pramod2
1Cardiac Surgery, Artificial Heart Laboratory, Yale School of Medicine, New Haven, CT, USA, 2Cardiac Surgery, Yale School of Medicine, New Haven, CT, USA
Continuous flow left ventricular assist devices (LVAD) have demonstrated increased durability and improved survival for the CHF patients compared to earlier pulsatile pumps. However presence of non-physiologic continuous flow has been implicated in the increased incidence of gastrointestinal bleeding and aortic incompetence seen in this patient population. While observations that myocardial recovery happens less often with continuous flow pumps has raised concerns regarding using such technology in less sick patients with a potential for myocardial recovery.
We have previously shown the feasibility of a totally implantable, wirelessly powered LVAD device using a Free-range Resonant Electrical Energy Transfer Delivery (FREE-D) system. A totally implantable system must weigh the risks of increased hardware necessary for implantation such as the controller size and back-up battery. In the present investigation, we demonstrate the innovation with an ultra-compact microcontroller (UMC-Physio) capable of pulsed operation in a rotary pump with wireless communication to a graphical user interface outside the body.
The three phase axial pump (HeartMate II) was used with an inline controller designed on an ultra-compact printed circuit board with embedded wireless algorithm to establish a communication network between the UMC-Physio and a graphical user interface to display the information and configuration settings on a computer or smartphone (Figure 1A, B & E). We employed signal processing and filtering methods to analyze EKG signal and adjust speed during systole and diastole for a co-pulsation, counter-pulsation or a fixed mode operation. Flow was estimated by recording the changes in power consumption and speed controlled by the UMC-Physio in a mock circulation loop (MCL). A suction event detection algorithm was incorporated in the system for additional safety. Finally, the UMC-Physio was tested and calibrated in combination with a HeartMate-II LVAD to ensure its accuracy.
Our tests results prove the system to be remarkably safe, accurate and efficient. The UCMC -Physio operated continuously for two weeks duration with excellent communication. Figure1C/D shows that the UMC-Physio produces a same pump speed and flow rate at lower power consumption than the HeartMate II controller. When used with EKG gating the UMC-Physio allows different modes of operation with instantaneous flow and RPM changes resulting in a pulsatile flow with adjustable pulse pressure. The driver works well with both axial and centrifugal pumps.
We have developed a driver capable of simulating physiological flow that works well with a conventional continuous flow pump. Additional flexibility of wireless powering and communication with a user-friendly graphic display with a very small footprint makes this an ideal totally implantable LVAD system.
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