Development of a Mechanical Circulatory Support System

Although the only non-palliative therapy for end-stage heart failure is heart transplantation, the donor-recipient mismatch severely limits the effective application of the procedure. Mechanical Circulatory Support (MCS) Systems, which started to be developed since the early 60’s, are being used increasingly more often as bridge-to-transplant or as destination therapy in this cohort of patients in Turkey and worldwide. Today these systems, which consist of a blood pump unloading the left ventricle, an actuator that imparts energy to the pump, a pneummatic or electromechanic power source, a control unit, and accessories such as grafts, connectors, cables, have been miniaturized and converted into portable, totally implantable, robust, dependable and smart technologies.

In Turkey, as in most developing countries, development of competitive MCS systems locally is a medical, humanitarian need, as well as a scientific, technological and economic necessity. This project is being submitted in an attempt to develop an innovative MCS system as a national and original solution to this problem. A single-stage axial turbine and a brushless DC motor actuating the turbine’s rotor will constitute the Sub-Components (SC) of the Left Ventricular Assist Device (LVAD), which is the first Basic Technological Component (BTC1) of the proposed System. The original geometry of the turbine, developed in preliminary studies, will be optimized numerically (Computational Fluid Dynamics, CFD) and manufactured on a 3-D printer out of Ti6Al4V in the initial phase of the Main Project. Prior to being integrated with the motor, the flow fields and shear stress areas over the rotor and stator blades will be visualized using optical techniques (Particle Image Velocimetry, PIV), as the turbine will be connected to a hydraulic circuit and actuated on the External Driving Mechanism. The solid model will be optimized until CFD-PIV iterations converge. As part of the Sub-Project 1, and simultaneously with the Main Project, the motor will be developed using low-conductance Titanium alloy and high energy-density magnets. Parasitic Titanium losses and magnet losses willl be minimized with the innovative application of material  segmentation, while system efficiency will be increased by encapsulating the stator, thus rendering the blood-contacting surfaces of the air gap less porous. The two Sub-Components of the System Control Unit (BTC2), which will be developed under Sub-Project 2, will be the Ergonomic Patient Interface and the Two-Way Data Communication Protocol. The Protocol will stream real-time values of important physiologic and electeomechanic variables to the patient interface and to the nursing (or monitoring) station (encrypted); and also, originally, allow for remote professional intervention should a medical emergency arise.  The Controller embedded in the Control Unit is the third component of the Unit, and will be developed as part of the Main Project. The Controller will have a superior design incorporating a non-linear adaptive backstepping control algorithm, which allows stable and robust control of the turbine speed while, concurrently, avoiding adverse events such as hemolysis or ventricular suction caused by excessive speeds, or pump thrombosis or tissue ischemia caused by speeds too low.  The System, its Basic Technological Components, and their Sub-Components will be verified and validated in the operational environment provided by an advanced cardiovascular Mock Circuit, capable of simulating with high accuracy normal resting and exercise conditions. The Circuit will constitute the third BTC of the project, and will be developed as part of the Main Project. It will operate based on the Pontryagin Maximum Principle (PMP) so as to determine the time-varying elastance (pressure-volume relationship) of the left ventricle, which maximizes left ventricular hydraulic efficiency on a beat-to-beat basis. The fact that left ventricular function will be derived analytically using one of the most powerful techniques of Optimal Control Theory, rather than through an empirical elastance formula fed as an input into the system as is done in the literature to-date, is expected to offer an effective, applicable and original platform for testing LVAD performance. 

The Principle Investigator of the present proposal has close to twenty years of research and administrative experience at the Texas Heart Institute (THI) in Houston, TX, one of the most advanced MCS centers in the world. During that time, he has actively participated in the design, testing and experimental and clinial trial stages of most MCS systems in the world, among them HeartMate-II and HeartWare.

The Surgical Consultant of the project, Dr. M. Hakan Akay, has been trained in the THI Heart Transplant, Heart Failure and MCS services of Drs. Denton A. Cooley and Bud H. Fraizer, two of the most experienced and highly respected cardiac surgeons in the world. He is currently the Surgical Director of the Advanced Heart Failure Center of Memorial Hermann Hospital in Houston, TX.

Professor Erkan Meşe, Co-Investigator and Director of Sub-Project I in the current proposal, is an internationally renowned expert in the field of Electrical Machinery, and a scholar with many important scientific papers, inventions and technical patents.

Dr. Türker Türker is a young, successful, dynamic and productive  academician, who is beginning to make a name for himself in the field Non-Linear Control.

The expertise and theoretical strength of the academic team, and the know-how and field experience of the Industrial Partner are factors that combine to ensure the success of the project, which aims at arriving to the design-freeze phase (end of TRL6) of a robust and dependable prototype ready for biological testing. Created by an able and motivated team using 100% national resources, the technology is expected to have a high medical, scientific, industrial and economical  impact

Keywords: Heart Failure, Mechanical Circulatory Assistance, Left Ventricular Assist Device, Cardiovascular Simulation Circuit, Time-varying Left Ventricular Elastance, Mechanical Circulatory Assistance, Adaptive Backstepping Control, Brushless Motor Design, Bidirectional Wireless Communication, Pontryagin Maximum Principle