Circuit for detection of the presence of a permanent magnet in the vicinity of an active medical device, in particular a pacemaker, defibrillator, cardiovertor and/or multisite device

A circuit for detecting the presence of a permanent magnet in the vicinity of an active medical device comprising:

• a coil having a first inductance in the absence of a proximate permanent magnet and a reduced inductance in the presence of a permanent magnet proximate to the coil;
• a resonant LC circuit including said coil;
• a pulse generator for pulse excitation of said resonant circuit;
• means for analyzing a pulse response of the resonant circuit to said pulse excitation, and
• discriminating means, able to evaluate the value of the coil inductance resulting from the analyzed pulse response and, correlatively, to determine a presence and an absence of the proximate permanent magnet,
• characterized in that:
• the pulse generator comprises means able to deliver a burst of N successive pulses, and the analyzing means comprises means able to determine N corresponding pulse responses, and the discriminating means comprises means able to determine the presence of the permanent magnet if, among N determined analyzed pulse responses, a number M of said determined analyzed pulse responses correspond to said reduced value of inductance, wherein M is less than N.