Dynamic cardiomyoplasty using artificial muscle

New Insights in the Diagnosis and Treatment of Heart Failure

Cardiovascular disease is the leading cause of mortality in the US and in westernized countries with ischemic heart disease accounting for the majority of these deaths. Paradoxically, the improvements in the medical and surgical treatments of acute coronary syndrome are leading to an increasing number of “survivors” who are then developing heart failure. Despite considerable advances in its management, the gold standard for the treatment of end-stage heart failure patients remains heart transplantation. Nevertheless, this procedure can be offered only to a small percentage of patients who could benefit from a new heart due to the limited availability of donor organs. The aim of this review is to evaluate the safety and efficacy of innovative approaches in the diagnosis and treatment of patients refractory to standard medical therapy and excluded from cardiac transplantation lists.

INVESTIGATION OF SHAPE MEMORY ALLOY SPRING ELASTIC COEFFICIENT BASED ON VARYING APPLIED CURRENTS IN A CARDIAC ASSIST DEVICE

This paper analyses the mechanical properties of shape memory alloy (SMA) springs based on different electric currents applied in a cardiac assist device (CAD). Experimental results show that when the input drive current is constant, the SMA spring is equivalent to a tension spring with determined elastic coefficient that increases with the current. Based on our experiments, the theoretical maximum recovery force produced by SMA can be obtained through this input current. The phase transformation of SMA from austenite to martensite is able to be controlled by the drive current instead of the surface temperature of SMA. In addition, this experiment designed a cardiac supporting device composed of eight SMA springs, and used a saline bag to simulate human heart. The peak pressure inside the saline bag produced by this device was 17.4% of the normal heart systolic pressure. Our results can provide further support for the research of advanced CAD.

Beyond heart transplantation: potentials and problems of the shape memory alloy fibers in the treatment of heart failure

Heart failure can be treated with devices that mechanically support the circulation. The improvement of these devices would benefit many patients, especially those refractory to maximal pharmacological treatment and ineligible for heart transplantation. This study examined whether the shape memory alloy (SMA) fibers, which are fibers that contract when electric current flows through them and relax passively when that flow is interrupted, can be wrapped around the failing heart and assist in its pumping action. A band of SMA fibers was wrapped around a silicon cylindrical chamber which simulated a dilated heart and its pumping action was tested in a circulatory mockup. This rudimentary device was innovatively controlled by pulse width modulation. The band was made of only six fibers but yet produced the considerable pressure of 20 mm Hg and a stroke volume of 11.8 ml with modest energy demands. A SMA device could assist a severely failing heart, but there are limiting factors to overcome before designing highly effective devices.

Artificial heartbeat: design and fabrication of a biologically inspired pump

We present a biologically inspired actuator exhibiting a novel pumping action. The design of the 'artificial heartbeat' actuator is inspired by physical principles derived from the structure and function of the human heart. The actuator employs NiTi artificial muscles and is powered by electrical energy generated by microbial fuel cells (MFCs). We describe the design and fabrication of the actuator and report the results of tests conducted to characterize its performance. This is the first artificial muscle-driven pump to be powered by MFCs fed on human urine. Results are presented in terms of the peak pumping pressure generated by the actuator, as well as for the volume of fluid transferred, when the actuator was powered by energy stored in a capacitor bank, which was charged by 24 MFCs fed on urine. The results demonstrate the potential for the artificial heartbeat actuator to be employed as a fluid circulation pump in future generations of MFC-powered robots ('EcoBots') that extract energy from organic waste. We also envisage that the actuator could in the future form part of a bio-robotic artwork or 'bio-automaton' that could help increase public awareness of research in robotics, bio-energy and biologically inspired design.

Artificial muscle for end-stage heart failure

We describe a device made of artificial muscle for the treatment of end-stage heart failure as an alternative to current heart assist devices. The key component is a matrix of nitinol wires and aramidic fibers called Biometal muscle (BM). When heated electrically, it produces a motorless, smooth, and lifelike motion. The BM is connected to a carbon fiber scaffold, tightening the heart and providing simultaneous assistance to the left and right ventricles. A pacemaker-like microprocessor drives the contraction of the BM. We tested the device in a dedicated bench model of diseased heart. It generated a systolic pressure of 75 mm Hg and ejected a maximum of 330 ml/min, with an ejection fraction of 12%. The device required a power supply of 6 V, 250 mA. This could be the beginning of an era in which BMs integrate or replace the mechanical function of natural muscles.