Magnetic Sensor for Early Detection of Heart Valve Bioprostheses Failure

Heart valve bioprostheses usually do not need anticoagulation; however they are threatened by an increasing with time risk of degeneration. The aim of this work is to find a magnetic sensor, which could be integrated in a bioprosthesis, monitoring the prosthesis in such a way that allows to confidently forecast the failure. Several models of magnetic sensors have been tested in a hydrodynamic setup specifically manufactured, where the heart pressure, frequency, and cardiac flow were simulated. Small pieces of amorphous soft magnetic material were stuck to the cusps of a bioprosthesis, and through a carefully designed electronic system, the movement of the cusps is detected at the same time that the image of the working valve is captured by a digital camera. The small pieces placed in the valve are under an external applied field of few Khz, and the magnetization signal of the pieces is acquired by means of two series connected coils. The movement of the pieces, at a cardiac simulated rhythm, induces a modulation in the amplitude of the signal detected in the secondary coils, with the same frequency as the valve movement. The modulated signal is analysed with a system consisting of an amplifier and a synchronous demodulator. The analysis of the electronic signal together with the image allows characterizing the signal changes when the valve begins to fail, preventing the bioprosthesis functional failure.