System and method for measuring cardiac activity
First Claim
1. An implantable cardiac stimulation device having a hermetically sealed housing, the device comprising:
- pulse generating means for generating therapeutic stimulation pulses to a patient'"'"'s heart;
sensing means, mounted within the housing, for sensing acceleration of the cardiac wall resulting from the patient'"'"'s heartbeat and for providing a cardiac wall acceleration signal indicative thereof;
means for integrating the cardiac wall acceleration signal twice to produce a cardiac wall displacement signal; and
control means, coupled to the pulse generating means and the integrating means, for controlling the delivery of the therapeutic stimulation pulses to the patient'"'"'s heart and for altering the delivery of therapeutic stimulation pulses based, at least in part, on the cardiac wall displacement signal.
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Accused Products
Abstract
An implantable cardiac stimulation device, such as a pacemaker or an implantable cardioverter-defibrillator, that includes an accelerometer-based activity sensor that processes one or more signals from the activity sensor to obtain parameters that are indicative of the heartbeat of the patient. The implantable cardiac stimulation device determines when the patient is at rest and the activity sensor provides a signal that corresponds to the acceleration of the sensor due to the heartbeat of the patient. This acceleration signal is integrated over time once to provide a contractility parameter, which is indicative of the contractility of the heart and is integrated over time twice to provide a displacement parameter, which is indicative of the displacement of the heart wall during the heartbeat. This displacement parameter is thereby indicative of the volume of blood pumped by the heart. A microprocessor uses either the contractility parameter, the displacement parameter or both to modify the delivery of therapeutic stimulation pulses to the heart.
215 Citations
23 Claims
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1. An implantable cardiac stimulation device having a hermetically sealed housing, the device comprising:
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pulse generating means for generating therapeutic stimulation pulses to a patient'"'"'s heart; sensing means, mounted within the housing, for sensing acceleration of the cardiac wall resulting from the patient'"'"'s heartbeat and for providing a cardiac wall acceleration signal indicative thereof; means for integrating the cardiac wall acceleration signal twice to produce a cardiac wall displacement signal; and control means, coupled to the pulse generating means and the integrating means, for controlling the delivery of the therapeutic stimulation pulses to the patient'"'"'s heart and for altering the delivery of therapeutic stimulation pulses based, at least in part, on the cardiac wall displacement signal. - View Dependent Claims (2, 3, 4, 5)
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6. A method of regulating the delivery of therapeutic electrical stimulation pulses to a patient'"'"'s heart from an implantable cardiac stimulation device having a housing with an accelerometer-based sensor mounted therein, the method comprising the steps of:
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sensing a first acceleration signal corresponding to the mechanical contraction of the heart with the accelerometer-based sensor mounted in the housing; processing the first acceleration signal to produce a cardiac wall displacement signal which is indicative of the volume of blood provided by the heart during a single heartbeat; providing a first control signal based on the cardiac wall displacement signal; and modifying the delivery of therapeutic stimulation pulses to the heart based, at least in part, on the first control signal. - View Dependent Claims (7, 8, 9, 10, 11, 12)
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13. An implantable cardiac stimulation device having a hermetically sealed housing, the device comprising:
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pulse generating means for generating therapeutic stimulation pulses to a patient'"'"'s heart; sensing means, mounted within the housing, for sensing acceleration and for providing an acceleration signal indicative thereof; detection means for detecting a low amplitude component of the acceleration signal corresponding to heart wall acceleration resulting from the patient'"'"'s heartbeat; integrating means for integrating the low amplitude component of the acceleration signal twice to produce a first control signal corresponding to a physical displacement of the cardiac wall of the heart; and control means, coupled to the pulse generating means and the integrating means, for controlling the delivery of the therapeutic stimulation pulses to the patient'"'"'s heart and for altering the delivery of therapeutic stimulation pulses based, at least in part, on the first control signal. - View Dependent Claims (14, 15, 16, 17, 18, 19)
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20. An implantable cardiac stimulation device having a hermetically-sealed housing, the device comprising:
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an accelerometer, mounted within the housing, that senses acceleration of the cardiac wall resulting from a patient'"'"'s heartbeat, the accelerometer producing a cardiac wall acceleration signal as an output; signal processing circuitry, coupled to the accelerometer, that integrates the cardiac wall acceleration signal twice to produce a cardiac wall displacement signal; a pulse generator circuit that generates stimulation pulses to the patient'"'"'s heart in response to a trigger signal which defines a timing between the stimulation pulses; and a control circuit, coupled to the pulse generator circuit and the signal processing circuitry, configured to modulate the timing of the stimulation pulses in response to the cardiac wall displacement signal. - View Dependent Claims (21, 22, 23)
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Specification