Electromagnetic acceleration transducer for implantable medical device

A pacemaker lead, comprising:

• a first electrode;
• and
• an electromagnetic accelerometer, said
• electromagnetic accelerometer comprising
• a rigid shell including an inner wall defining a cavity,
• a first magnet disposed within said cavity and fixedly mounted with respect to said rigid shell;
• a second magnet slidingly disposed within said cavity;
• and
• a third magnet disposed within said cavity and fixedly mounted with respect to said rigid shell;
• said second magnet reciprocating between said first and third magnets;
• and
• means for detecting movement of said second magnet within said cavity.

An implantable medical device, comprising:

• a housing;
• at least one lead coupled to said housing and including a first electrode;
• at least one electromagnetic accelerometer producing an output signal;
• said electromagnetic accelerometer further comprising a shell including an inner wall defining a cavity,
• a first magnet disposed within said cavity and fixedly mounted with respect to said shell;
• a second magnet slidingly disposed within said cavity;
• and
• a third magnet disposed within said cavity and fixedly mounted with respect to said shell;
• said second magnet reciprocating between said first and third magnets;
• and means for detecting movement of said second magnet within said cavity;
• means connected to said lead for producing an electrical stimulation;
• and means in electrical communication between said accelerometer and said stimulation producing means for modifying said stimulation as a function of said output signal of said accelerometer.

An accelerometer, comprising:

• a housing;
• a first magnet retained in a fixed position within said housing and having a first end of a first predetermined polarity;
• a second magnet retained in a fixed position within said housing and spaced apart from said first magnet and having a first end of a second predetermined polarity;
• a third magnet in said housing and disposed between said first and second magnets such that the end of said third magnet that is closest to said first magnet is of first predetermined polarity and also such that the end of said third magnet that is closest to said second magnet is of said second predetermined polarity, said third magnet being mounted so as to be free to reciprocate between said first and second magnets, and
• a coil of wire for sensing motion of said third magnet, said coil including a first portion and a second portion, said first portion being disposed about the first end of the first magnet and a part of said third magnet and wound in a first direction and said second portion being disposed about the first end of the second magnet and a part of said third magnet and wound in a second direction.