Cardiac electrical activity is mainly evaluated by monitoring the electrical biosignals. This requires a long-lasting power supply to make implantable devices cost-effective and efficient. Since the current trend is to implant catheter-free stand-alone electrodes (implantable cardiac monitors), the need for smaller devices is at odds with the need for long-life batteries. To avoid these problems, we propose a passive endocardial sensor able to monitor the movement of the considered chamber based on a permanent magnet shaped for implantation in the internal chamber of the heart (i.e. the right atrium) and an external gauss meter unit to measure sensor-induced magnetic field variations. Since the magnet is permanent, no replacement is needed after the first implant, thereby reducing the risks linked to invasive procedures, and the battery in the external device can be substituted more easily. To test our idea we used a permanent magnet mounted on the tip of a commercial catheter for heart mapping together with a dedicated gauss meter built in our laboratory. The device was tested in vitro and the magnetic field variations were acquired and measured in different conditions of movement and distances. The results demonstrate the feasibility of our approach and open an interesting new scenario where permanent magnets can be used to monitor the mechanical behaviour of the heart.
