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Abstract

A variable rate cardiac pacer apparatus is responsive to the physical activity of the patient. A source of alternating current carrier signals of a predetermined frequency is coupled to the pacer housing. At least one sensing electrode is coupled to the carrier signals. The sensing electrode and the pacer housing are structured and arranged to operate as a pair of interface sensing electrodes. A sense amplifier apparatus is coupled to the sensing electrodes for receiving and amplifying modulated electrical signals developed across the sensing electrodes. A demodulator circuit apparatus is structured and arranged to receive the amplified modulated carrier signal which is proportional to the impedance field around the sensing electrode. The frequency of the demodulated signal is proportional to the patient's rate of movement. A signal processing apparatus receives the demodulated signal and provides a processed signal proportional to impedance changes sensed at the interface. A rate control apparatus determines the rate at which the heart stimulating pulse will be generated in response to the processed signal.

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First Claim