In Vivo Performance of a Muscle-Powered Drive System for Implantable Blood Pumps

Abstract

A unique biomechanical implant has been developed to convert muscle power into hydraulic energy for the purpose of driving an implanted blood pump. This device, called a muscle energy converter (MEC), is designed to attach to the humeral insertion of the latissimus dorsi (LD) muscle, so that stimulated contractions cause a rotary cam to compress a fluid-filled bellows. Here we report results from the latest in a series of canine implant trials where the MEC was connected to an adjustable pressure load to measure power output and assess long-term function. Full-length (2 cm) actuator strokes were maintained for a period of 1 month with no discernable discomfort to the animal. Load conditions were cycled periodically to measure stroke work capacity and pressure production. The peak driveline pressure recorded in this experiment was 1743 mm Hg. Steady state power generation was measured to 478 +/- 21 mJ/stroke (mean +/- SD) with stroke work levels reaching 785 mJ in one test. Normal left and right ventricular stroke work levels in dogs this size (35 kg) are 700 and 150 mJ, respectively. These data confirm that MEC/LD power levels--maintained in tandem with an appropriate cardiac assist device--are sufficient to provide significant long-term circulatory support. Further testing, however, is still needed to demonstrate the long-term stability of this drive system.

In Vivo Demonstration of a Self-Sustaining, Implantable, Stimulated-Muscle-Powered Piezoelectric Generator Prototype

“…The mechanical power associated with a 23 μ m displacement of a piezoelectric stack, using a 100 N, 0.25 s, 1 Hz triangular force pulses is 0.3 mW. A 60 N peak force and 2 cm displacement can produce a mechanical power of 0.15 W,51 which is an increase of a factor of approximately 500. Therefore, it is worth exploring mechanical to electrical conversion devices that would operate with optimal muscle force and stroke.…”

Artificial Muscles and Soft Robotic Devices for Treatment of End‐Stage Heart Failure

“…Such a device has been estimated to exert pressures in the range of 0-33 kPa at a flow rate of 0-30 m s −1 , producing an actuation force between 0 and 14 N. [81] The Whitaker foundation and the NIH reported a muscle energy converter device that can produce 1.37 J of contractile work per stroke. [91][92][93][94] The research work of Trumble [95] outlined different approaches for designing the device and the associated power requirements. The first method is an extra aortic counter pulsation which may lead to thrombosis in the long term.…”

Potential Mechanisms for Muscle‐Powered Cardiac Support

“…Extracorporeal drive systems for long‐term ventricular assist devices (VADs) continue to be problematic in terms of infection risk and patient quality of life. To address these problems, work to develop an implantable muscle energy converter (MEC) for transforming the contractile energy of the latissimus dorsi (LD) muscle into hydraulic power has been underway for over a decade under the auspices of the Whitaker Foundation and the National Institutes of Health (1–3). This research has yielded a device with good anatomic fit, mechanical durability, and energy transfer efficiency (Fig.…”