Apparatus and method for adjusting heart/pacer rate relative to cardiac pCO.sub.2 to obtain a required cardiac output
First Claim
1. An implantable apparatus for pacing a heart in accordance with the heart/pacer rate needed to produce a required cardiac output relative to the partial pressure of carbon dioxide in blood, pCO2, while the person having the apparatus implanted within his body is exercising comprising:
- a demand pacer for implantation in the human body and having a pulse generator and control circuitry mounted therein and operable to sense, through a pacing lead, when a heart is not naturally paced;
a pacing lead for implantation in a heart and coupled to said pacer, said pacing lead having a tip electrode for engaging and supplying pacing pulses to a ventricle of a heart and having an opening therein which is located in a portion of the lead which is received in a heart chamber when the lead is implanted in a heart;
pCO2 sensing means mounted in said opening for sensing the partial pressure (tension) of CO2 dissolved in the blood and generating signals related to the pCO2 sensed; and
said control circuitry comprising a microprocessor including means for relating a signal from the pCO2 sensing means to the partial pressure of carbon dioxide, pCO2, in the blood, means for determining changes in the partial pressure of carbon dioxide, Δ
pT CO2, and relating such changes to a corresponding change in pacing rate, Δ
RT, between a maximum rate increase allowed, Δ
RMax.1, and a maximum rate decrease allowed, Δ
RMax.2, means for adjusting the pacing rate, Δ
RT-1, by adding Δ
RT to the present pacing rate, RT-1, to obtain a new pacing rate, RT, between a minimum programmed pacing rate, RMin. and a maximum programmed pacing rate, RMax., needed to supply a required cardiac output relative to the pCO2 measured, and means for causing the pacer to pace the heart at the newly calculated required rate when the heart is not naturally paced while the person is exercising.
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Accused Products
Abstract
The apparatus for pacing a heart in accordance with the heart rate needed to produce a required cardiac output relative to the partial pressure of carbon dioxide in the blood, pCO2, while the person is exercising comprises a pacer adapted to be implanted in a human body and having a pulse generator and control circuitry (e.g. including a microprocessor) therein, a pacing lead adapted to be implanted in a heart and having a distal electrode adapted to engage and supply pacing pulses to a right ventricle of a heart and a pCO2 sensor for sensing pCO2 of the blood in the heart. An algorithm and routine utilizing same are stored in the control circuitry (microprocessor) and are adapted to relate pCO2 with the required heart rate or change in rate, ΔR, needed to supply a desired cardiac output and to cause the pacer to pace the heart at the required heart rate when the heart is not naturally paced.
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Citations
22 Claims
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1. An implantable apparatus for pacing a heart in accordance with the heart/pacer rate needed to produce a required cardiac output relative to the partial pressure of carbon dioxide in blood, pCO2, while the person having the apparatus implanted within his body is exercising comprising:
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a demand pacer for implantation in the human body and having a pulse generator and control circuitry mounted therein and operable to sense, through a pacing lead, when a heart is not naturally paced; a pacing lead for implantation in a heart and coupled to said pacer, said pacing lead having a tip electrode for engaging and supplying pacing pulses to a ventricle of a heart and having an opening therein which is located in a portion of the lead which is received in a heart chamber when the lead is implanted in a heart; pCO2 sensing means mounted in said opening for sensing the partial pressure (tension) of CO2 dissolved in the blood and generating signals related to the pCO2 sensed; and said control circuitry comprising a microprocessor including means for relating a signal from the pCO2 sensing means to the partial pressure of carbon dioxide, pCO2, in the blood, means for determining changes in the partial pressure of carbon dioxide, Δ
pT CO2, and relating such changes to a corresponding change in pacing rate, Δ
RT, between a maximum rate increase allowed, Δ
RMax.1, and a maximum rate decrease allowed, Δ
RMax.2, means for adjusting the pacing rate, Δ
RT-1, by adding Δ
RT to the present pacing rate, RT-1, to obtain a new pacing rate, RT, between a minimum programmed pacing rate, RMin. and a maximum programmed pacing rate, RMax., needed to supply a required cardiac output relative to the pCO2 measured, and means for causing the pacer to pace the heart at the newly calculated required rate when the heart is not naturally paced while the person is exercising. - View Dependent Claims (2, 3, 4, 5)
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6. An implantable apparatus for pacing a heart in accordance with the heart/pacer rate needed to produce a required cardiac output relative to the partial pressure of carbon dioxide in the blood, pCO2, while the person having the apparatus implanted within his body is exercising comprising:
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a demand pacer for implantation in the human body and having a pulse generator and control circuitry mounted therein and operable to sense, through a pacing lead, when a heart is not naturally paced; a pacing lead for implantation in a heart and coupled to said pacer, said pacing lead having a tip electrode adapted to engage and supply pacing pulses to a ventricle of the heart when the lead is placed in a heart and having an opening therein which is located in a portion of the lead which is received in a heart chamber when the lead is placed in a heart; said opening containing a pCO2 sensor comprising a CO2 permeable membrane which will make contact with the blood in a heart when the lead is placed in a heart and forming one side of a chamber having a liquid solution therein, a pH electrode on the other side of said chamber, a solid state reference electrode positioned within said chamber, and means for supplying voltage to said pH electrode and to said reference electrode whereby the potential between said pH electrode and said reference electrode is changed by the amount of free hydrogen ions in the liquid solution and such change in potential is directly related to the pCO2 of the blood in a heart; and said control circuitry comprising a microprocessor for relating the drain-source current to the partial pressure of carbon dioxide, pCO2 in the blood, means for determining changes in the partial pressure of carbon dioxide, Δ
pCO2, and relating such changes to a corresponding change in pacing rate, Δ
RT, between a maximum rate increase allowed, RMax.1, and a minimum rate decrease allowed, RMax.2, means for adjusting the pacing rate, RT-1, by adding Δ
RT to the present pacing rate, RT-1, to obtain a new pacing rate, RT, between a minimum programmed pacing rate, RMin. and a maximum programmed pacing rate, RMax., needed to supply a desired cardiac output relative to the pCO2 measured, and means for causing the pacer to pace the heart at the newly calculated required rate when the heart is not naturally paced while the person is exercising. - View Dependent Claims (7, 8, 9)
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10. A method for pacing a heart in accordance with the heart rate needed to produce a required cardiac output relative to the partial pressure of carbon dioxide in the blood, pCO2, while a person, whose heart is being paced, is exercising, said method comprising the steps of:
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implanting a demand pacer in a human body having a pulse generator and control circuit mounted therein; implanting a pacing lead in a heart and coupling said lead to said pacer, said pacing lead having a tip electrode; positioning said tip electrode to engage in and supply pacing pulses to a ventricle of the heart; providing said pacing lead with an opening therein a portion of the lead which is received in the heart; mounting pCO2 sensing means in the opening in the lead; sensing the pCO2 in the heart with the pCO2 sensing means; determining with said control circuitry the partial pressure of carbon dioxide, pCO2, in the blood from signals from asid PCO2 sensing means; determining the required pacing rate needed to supply a desired cardiac output relative to the sensed pCO2 including the steps of; determining values of pCO2 sensed; determining changes in pCO2 sensed; relating the change, Δ
pT CO2, to a corresponding change in heart rate, Δ
RT, between a maximum rate increase allowed, RMax.1, and a minimum rate decrease allowed, RMax.2 ;adjusting the pacing rate, RT-1, by adding Δ
RT to the present pacing rate, RT-1, to obtain a new pacing rate, RT, between a minimum programmed pacing rate, RMin. and a maximum programmed pacing rate, RMax ; andcausing the pacer to pace the heart at the newly calculated required pacing rate, RT, when the heart is not naturally paced. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
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18. A method for pacing a heart in accordance with the heart rate needed to produce a required cardiac output, while a person, whose heart is being paced, is exercising, relative to the partial pressure of carbon dioxide in blood, pCO2, said method comprising the steps of:
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implanting a demand pacer in a human body and having a pulse generator and control circuitry mounted therein; implanting a pacing lead in a heart and coupling said lead to said pacer, said pacing lead having a tip electrode; positioning said tip electrode to engage in and supply pacing pulses to a ventricle of the heart; providing said pacing lead with an opening therein in a portion of the lead which is received in the heart; mounting a pCO2 sensor in said opening comprising a chamber having a liquid solution therein, a CO2 permeable membrane on one side of said chamber which will make contact with the blood in a heart when the lead is placed in a heart, a pH electrode on the other side of said chamber, a solid state reference electrode positioned within said chamber, and, means for supplying a voltage to said pH electrode and to said reference electrode whereby the potential between said pH electrode and said reference electrode is changed by the amount of free hydrogen ions in the liquid solution and such change in potential is directly related to the pCO2 of the blood in the heart; sensing the pCO2 in the heart with the pCO2 sensor; and determining with said control circuitry the drain-source current to the partial pressure of carbon dioxide, pCO2, in the blood; determining the required pacing rate needed to supply a desired cardiac output relative to the sensed pCO2 including the steps of; determining values of pCO2 sensed; determining changes in pCO2 sensed relating the change, Δ
pT CO2, to a corresponding change in heart rate, Δ
RT, between a maximum rate increase allowed, RMax.1, and a maximum rate decrease allowed, RMax.2 ;adjusting the pacing rate, RT-1, by adding Δ
RT to the present pacing rate, RT-1, to obtain a new pacing rate, RT, between a minimum programmed pacing rate, RMin., and a maximum programmed pacing rate, RMax. ; andcausing the pacer to pace the heart at the newly calculated required pacing rate, RT, when the heart is not naturally paced. - View Dependent Claims (19, 20, 21, 22)
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Specification