Exercise-responsive cardiac pacemaker lead

A catheter-based sensor and stimulus means for an exercise responsive cardiac pacemaker including pacing circuitry for providing electrical stimulation of a heart based upon the level of muscular exertion, comprising:

• a thermistor for sensing blood temperature, said thermistor having a pair of electrical leads;
• a stimulus means for applying an electrical stimulus to a heart;
• a catheter associated with said thermistor and said stimulus means, said catheter having at least one lumen therethrough;
• and
• an electrical conductor means for operatively connecting said stimulus means and said thermistor to control circuitry for said exercise responsive cardiac pacemaker in such manner that the frequency of said electrical stimulus is controlled by said blood temperature as sensed by said thermistor, said electrical conductor means including a bifilar coil wire connected to said stimulus means, a pair of bifilar coil wires associated with said electrical leads of said thermistor, and a pair of rigid conductive tubing sections joining said pair of bifilar coil wires to said pair of leads, respectively,
• wherein said thermistor is coated with glass, encased within epoxy and received in a lumen of said catheter which is at least partially filled with an elastomer, said stimulus means is mounted on the distal end of said catheter, and wherein said thermistor is received within said lumen and located relative to said stimulus means such that when said stimulus means is positioned within said heart for electrical stimulation thereof, said thermistor is centrally positioned within the right ventricle of said heart.