MiTiHeart Corporation

Technical Details:

The MiTiHeart™ LVAD is based on an optimal magnetic bearing support system that is totally non-contact. A magnetic bearing support system has advantages from the viewpoints of power loss and blood damage. With this novel design, the power loss of a magnetic bearing can be extremely low, especially compared to a hydrodynamic bearing system. Most active magnetic bearing supported pumps use a magnetic bearing system with five active axes (one axial, two radial, and two tilt) to provide complete control of the pump rotor during operation. The MiTiHeart™ design, however, uses a hybrid passive/active magnetic bearing system such that only one actively controlled axis is required. A reduction in the number of actively controlled axes reduces the power required to operate the bearings, thus increasing operating time before a battery change or recharge is required.

The prototype pump was fully tested in both vertical and horizontal orientations using a standard flow loop to demonstrate the performance and durability. The pump durability under both steady-state and transient conditions has been demonstrated. Steady state and transient orientation pump operating characteristics including pressure, flow, speed, temperatures, vibration and rotor orientation were measured. During the tests, pump performance was mapped at several operating conditions including points above and below the nominal design of 5 L/min at 100 mm Hg pressure rise. Flow rates from 2 L/min to 7 L/min and pressure rises from 50 to 150 mmHg were measured. Pump speeds were varied during these tests from 2,500 to 3,500 rpm. The nominal design flow of 5 L/min at 100 mmHg pressure rise was successfully achieved at the design speed of 3,000 rpm. Following performance testing, both 28-day continuous duty and 5-day transient orientation durability tests were completed without incident. Extremely low pump vibrations were observed in all cases.

Hemolysis testing of the prototype pump was performed in-house and also at the Hershey Medical Center. The test results indicated a very low normalized index of hemolysis of less than 0.005 much smaller than most LVADs currently in clinical use or pre-clinical testing.

Another unique feature of the MiTiHeart™ design configuration is the very simple and direct flow path for both main and washing blood flows. The non-contact nature of the magnetic bearing allows for fully washed flow paths to avoid stagnation points that might promote thrombi formation. Considerable flexibility in design of these flow paths can be obtained through variations in the magnetic bearing system design. With proper design, it becomes possible to both avoid stagnation points, while at the same time maintain large enough clearances throughout the flow path to also eliminate regions of local high shear stress. The low shear associated with the relatively large gaps between the rotating surfaces and lower speeds (3,000 rpm compared with 10,000 rpm in axial pumps) ensures low blood damage. Equally important, the use of non-contact bearings totally eliminates the lifetime reducing wear and tribocompatibility issues that are present in rolling element or point contact bearing systems.

Simplified Diagram of MiTiHeart™ LVAD

Rise in Pressure vs Flow

Axial Shock and Rotor Response

A Subsidiary of Mohawk Innovative Technology, Inc.

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