Abstract: A system is provided for cardiac pacing, in which the output levels of the electrical stimulus pulses are responsive to the detection or non-detection of cardiac pacer evoked potentials. A pulse generator is provided for emitting electrical stimulus pulses at variable output levels. A pulse to pulse interval and an evoked response sensing period are provided. At the beginning of the pulse to pulse interval, an electrical stimulus having a first output level is emitted. If no evoked response is sensed during the sensing period, then an electrical stimulus at a selected maximum output level is emitted and, thereafter, the next electrical stimulus pulse is emitted at a second output level that is greater than the first output level.

Abstract: A cardiac pacer is provided which incorporates a sensor responsive to the physical activity of the pacer-wearing patient. The output of the physical activity sensor is utilized by control circuitry of a physiological sensor to enable the physiological sensor to monitor a selected physiological parameter only if the physical activity of the pacer-wearing patient exceeds a selected threshold. In this manner, the electrical energy requirements of the pacer are lessened.

Abstract: Automatic detection of cardiac pacer evoked potentials may be obtained through a cardiac pacer lead positioned in a heart chamber. An electrical stimulus is emitted in unipolar mode from a first electrode to stimulate muscular contraction. The cardiac electrical activity evoked by the stimulus is then detected in unipolar mode by a second electrode which is spaced from the first electrode and free of electrical connection thereto. Accordingly, signal interference caused by residual polarization of the first electrode is suppressed. The natural cardiac electrical activity is sensed in a bipolar mode, and the pulse is inhibited if a heartbeat is detected within an alert period.

Abstract: A rate responsive cardiac pacing system is provided. In the illustrative embodiment, electrical stimulus pulses are applied to the heart ventricle and the evoked potential of the applied electrical stimulus pulses is detected. The detected potential is integrated over time to obtain a depolarization gradient duration. The depolarization gradient duration is compared with a corresponding depolarization gradient duration of at least one previous cardiac cycle. The rate of the electrical stimulus pulses is controlled in response to this comparison.

Abstract: A rate responsive cardiac pacing system is provided. In the illustrative embodiment, electrical stimulus pulses are applied to the heart ventricle and the evoked potential of the applied electrical stimulus pulses is detected. The detected potential is integrated over time to obtain a depolarization gradient magnitude. The depolarization gradient magnitude is compared with a corresponding depolarization gradient magnitude of at least one previous cardiac cycle. The rate of the electrical stimulus pulses is controlled in response to this comparison.

Abstract: A rate responsive cardiac pacing system is provided. In the illustrative embodiment, electrical stimulus pulses are applied to the heart ventricle and the evoked potential of the applied electrical stimulus pulses is detected. The detected potential is integrated over time to obtain a repolarization gradient magnitude. The repolarization gradient magnitude is compared with a corresponding repolarization gradient magnitude of at least one previous cardiac cycle. The rate of the electrical stimulus pulses is controlled in response to this comparison.

Abstract: A rate responsive cardiac pacing system is provided. In the illustrative embodiment, electrical stimulus pulses are applied to the heart ventricle and the evoked potential of the applied electrical stimulus pulses is detected. The detected potential is integrated over time to obtain a depolarization gradient and a repolarization gradient. A peak to peak time interval is determined from the peak of the depolarization gradient to the peak of the repolarization gradient. The peak to peak time interval is compared to the peak to peak time interval of at least one previous cardiac cycle. The rate of the electrical stimulus pulses is controlled in response to this comparison.

Abstract: A system is provided for cardiac pacing and sensing. A lead carrying three electrodes is introduced into a cardiac chamber. Two of the electrodes are connected to the output of a pulse generator and are disconnected from the pulse generator output during sensing. All three of the electrodes are connected to the input of a sensing amplifier during sensing and two of the electrodes are disconnected from the input during pacing.