Rate responsive cardiac pacemaker and method for discriminating stair climbing from other activities
First Claim
1. A method of pacing a patient'"'"'s heart at a pacing rate dependent on patient activity and posture particularly during stair climbing comprising the steps of:
- deriving a body posture tilt signal having a characteristic varying with the degree to which the patient posture is in an upright stance or leaning forward;
detecting patient footsteps;
deriving a patient activity signal having a signal level dependent on the frequency of patient footsteps recurring over a time unit;
deriving a rate control signal from the body posture tilt signal and the patient activity signal correlated to the physiologic demand on the patient'"'"'s heart;
defining physiologic escape intervals as a function of the rate control signal to establish a physiologic pacing rate;
generating pacing pulses at the physiologic pacing rate; and
applying the pacing pulses to the patient'"'"'s heart.
1 Assignment
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Accused Products
Abstract
A method of and apparatus for pacing a patient'"'"'s heart at a pacing rate dependent on patient activity and posture particularly during stair climbing. A dual chamber, rate responsive pacemaker for pacing a patient'"'"'s heart includes at least one DC accelerometer mounted in the pacemaker pulse generator for implantation such that the sensitive axis of the DC accelerometer is sensitive to the effects of gravity during forward lean of the patient characteristic of stair climbing posture. The DC and AC signal outputs of the accelerometer are processed to develop a tilt signal and an activity signal. A target rate control signal is derived from the activity signal dependent on the level of activity. A stair climbing rate is selected for controlling the physiologic pacing rate between a lower and an upper pacing rate in the presence of an activity signal indicative of a patient walking rate and a tilt signal value falling within a tilt window. The target rate control signal is used to control the pacing rate if the activity signal is indicative of faster patient movement, e.g. running, or if the tilt signal is outside the tilt window indicating that the patient is either upright or prone.
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Citations
27 Claims
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1. A method of pacing a patient'"'"'s heart at a pacing rate dependent on patient activity and posture particularly during stair climbing comprising the steps of:
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deriving a body posture tilt signal having a characteristic varying with the degree to which the patient posture is in an upright stance or leaning forward; detecting patient footsteps; deriving a patient activity signal having a signal level dependent on the frequency of patient footsteps recurring over a time unit; deriving a rate control signal from the body posture tilt signal and the patient activity signal correlated to the physiologic demand on the patient'"'"'s heart; defining physiologic escape intervals as a function of the rate control signal to establish a physiologic pacing rate; generating pacing pulses at the physiologic pacing rate; and applying the pacing pulses to the patient'"'"'s heart. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 22)
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17. Apparatus for pacing a patient'"'"'s heart at a pacing rate dependent on patient activity and posture particularly during stair climbing comprising:
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means for deriving a body posture tilt signal having a characteristic varying with the degree to which the patient posture is in an upright stance or leaning forward; means for detecting patient activity and for deriving a patient activity signal having a signal level dependent on the frequency and magnitude of patient activity; means for deriving a rate control signal from the body posture tilt signal and the patient activity signal correlated to the physiologic demand on the patient'"'"'s heart; means for defining physiologic escape intervals as a function of the rate control signal to establish a physiologic pacing rate; means for generating pacing pulses at the physiologic pacing rate; and means for applying the pacing pulses to the patient'"'"'s heart. - View Dependent Claims (18, 19, 20, 21)
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23. In a pacemaker pulse generator adapted to be implanted in a patient'"'"'s body, apparatus for pacing a patient'"'"'s heart at a pacing rate dependent on patient activity and body posture particularly to provide adequate cardiac output during stair climbing comprising:
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means for responding to the force of gravity on the patient'"'"'s body and deriving a tilt signal therefrom of a polarity and magnitude representative of the degree to which the patient is leaning forward from an upright stance; means for measuring forces of acceleration in the patient'"'"'s body due to patient footsteps and deriving a patient activity signal therefrom representative of patient footsteps; means operable in the presence of the tilt signal and the activity signal for providing a stair climbing rate control signal correlated to the physiologic demand on the patient'"'"'s heart appropriate for patient stair ascending; means for defining physiologic escape intervals as a function of the stair climbing rate control signals to establish a physiologic pacing rate; means for generating pacing pulses at the physiologic pacing rate; and means for applying the pacing pulses to a chamber of a patient'"'"'s heart. - View Dependent Claims (24, 25, 26, 27)
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Specification