Multiple parameter rate-responsive cardiac stimulation apparatus
First Claim
1. A metabolic demand rate-responsive cardiac stimulation apparatus, comprising:
- means for pacing a patient'"'"'s heart at a controlled rate;
means for measuring impedance within the patient'"'"'s body, said impedance measuring means including means for applying multiple fixed frequencies of measuring currents between two points within said apparatus and means for measuring voltages in response to the application of said measuring currents, said measuring currents having frequency components within a range of from approximately 10 kilohertz to approximately 1000 megahertz;
means for controlling said impedance measuring means to limit the frequency components of the applied measuring currents to lie within at least one predetermined subrange of frequencies such that the measured voltage within each subrange of frequencies corresponds to a measurement of a metabolic demand parameter;
means for deriving at least one metabolic demand parameter from the measured voltage corresponding to each of said at least one predetermined subrange of frequencies; and
means for determining said controlled pacing rate in relation to the values of said at least one derived metabolic demand parameter.
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Abstract
A metabolic demand rate-responsive cardiac stimulation apparatus and method are disclosed which employ multiple physiological rate control parameters, such as respiratory minute volume, patient motion and cardiac stroke volume. The parameters are derived using a single standard pacing lead or transducer. The apparatus and method perform each physiological measurement by periodically applying a measuring current between two points within the apparatus. This measuring current has frequency components in a range of from approximately 10 kilohertz to 1000 megahertz. Application of this measuring current allows the apparatus to detect the voltage which arises from the applied current and, from the detected voltage, to measure the patient'"'"'s spatial impedance. For a particular measurement, the apparatus controls which physiological parameter is sensed by regulating the frequency content of the measuring current. The apparatus analyzes the physiological parameters to determine the best pacing rate in terms of characteristics such as response time and stability.
200 Citations
44 Claims
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1. A metabolic demand rate-responsive cardiac stimulation apparatus, comprising:
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means for pacing a patient'"'"'s heart at a controlled rate; means for measuring impedance within the patient'"'"'s body, said impedance measuring means including means for applying multiple fixed frequencies of measuring currents between two points within said apparatus and means for measuring voltages in response to the application of said measuring currents, said measuring currents having frequency components within a range of from approximately 10 kilohertz to approximately 1000 megahertz; means for controlling said impedance measuring means to limit the frequency components of the applied measuring currents to lie within at least one predetermined subrange of frequencies such that the measured voltage within each subrange of frequencies corresponds to a measurement of a metabolic demand parameter; means for deriving at least one metabolic demand parameter from the measured voltage corresponding to each of said at least one predetermined subrange of frequencies; and means for determining said controlled pacing rate in relation to the values of said at least one derived metabolic demand parameter. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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25. A method for pacing a rate-responsive cardiac stimulation apparatus at a rate determined by a patient'"'"'s metabolic demand, comprising the steps of:
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measuring impedance within the patient'"'"'s body, said impedance measuring step comprising the substeps of applying multiple fixed frequencies of measuring currents between two points within the apparatus and measuring voltages in response to the application of said measuring currents, said measuring currents having frequency components within a range from approximately 10 kilohertz to approximately 1000 megahertz; controlling the measuring frequency components of the applied measuring currents to lie within at least one predetermined subrange of frequencies such that the measured voltage within each subrange of frequencies corresponds to a measurement of a metabolic demand parameter; deriving at least one metabolic demand parameter from the measured voltage corresponding to each of said at least one predetermined subrange of frequencies; determining a controlled pacing rate in relation to the values of said at least one derived metabolic demand parameter; and pacing a patient'"'"'s heart at said controlled rate. - View Dependent Claims (26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43)
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44. A method for pacing a rate-responsive cardiac stimulation apparatus at a rate determined by a patient'"'"'s metabolic demand, comprising the steps of:
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measuring impedance within the patient'"'"'s body, said impedance measuring step comprising the substeps of applying multiple fixed frequencies of measuring voltages between two points within the apparatus and measuring currents in response to the application of said measuring voltages, said measuring voltages having frequency components within a range from approximately 10 kilohertz to approximately 1000 megahertz; controlling the measuring frequency components of the applied measuring voltages to lie within at least one predetermined subrange of frequencies such that the measured current within each subrange of frequencies corresponds to a measurement of a metabolic demand parameter; deriving at least one metabolic demand parameter from the measured current corresponding to each of said at least one predetermined subrange of frequencies; determining a controlled pacing rate in relation to the values of said at least one derived metabolic demand parameter; and pacing a patient'"'"'s heart at said controlled rate.
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Specification