Estimating cardiovascular pressure and volume using impedance measurements
First Claim
1. A method comprising:
- storing in a memory of an implantable medical device a plurality of relationships between volume and pressure, the plurality of relatioships comprising a relationship between volume and pressure in avascular lumen;
storing in the memory a plurality of relationships between impedence and volume;
measuring an impedance between at least two electrodes implanted within or proximate to a cardiovascular system of a patient;
enabling a control unit to select one of the stored plurality of relationships between volume and pressure and one of the stored plurality of relationships between impedence and volume based on at least one selection criterion; and
estimating by the control unit, a pressure of an element of the cardiovascular system based on the selected relationship between impedence and volume and the selected relationship between the volume and the pressure, wherein the relationship between the volume and the pressure comprises an elastance function derived from empirical data comprising historical data of the patient.
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Accused Products
Abstract
Techniques for estimating a cardiac chamber or vascular pressure based upon impedance are described. A device or system may measure an impedance between at least two electrodes implanted within or proximate to a cardiovascular system. The device or system may estimate a pressure of an element of the cardiovascular system based on a relationship between impedance and volume of the element, and based on a empirical relationship between the volume and the pressure. The device or system may also estimate the dimension of the element based on the impedance-volume relationship, or other characteristics based on the impedance. Because the impedance measurements may be obtained, in some examples, by using electrodes and leads implanted within the cardiovascular system and coupled to an implantable medical device, a practical estimation of a cardiovascular pressure can be obtained on a chronic basis without requiring the use other invasive sensors, such as micronanometer transducers.
61 Citations
41 Claims
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1. A method comprising:
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storing in a memory of an implantable medical device a plurality of relationships between volume and pressure, the plurality of relatioships comprising a relationship between volume and pressure in avascular lumen; storing in the memory a plurality of relationships between impedence and volume; measuring an impedance between at least two electrodes implanted within or proximate to a cardiovascular system of a patient; enabling a control unit to select one of the stored plurality of relationships between volume and pressure and one of the stored plurality of relationships between impedence and volume based on at least one selection criterion; and estimating by the control unit, a pressure of an element of the cardiovascular system based on the selected relationship between impedence and volume and the selected relationship between the volume and the pressure, wherein the relationship between the volume and the pressure comprises an elastance function derived from empirical data comprising historical data of the patient. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. An implantable medical device comprising:
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an impedance measurement module configured to measure an impedance between at least two electrodes implanted within a cardiovascular system of a patient; a memory configured to store data representing a relationship between impedance and volume, and a relationship between the volume and pressure, wherein the relationship between the volume and the pressure comprises an elastance function derived from empirical data comprising historical data of the patient, the memory storing a plurality of relationships between volume and pressure, the plurality of relationships comprising a relationship between volume and pressure in a vascular lumen, the memory storing a plurality of relationships between impedance and volume; and a processor configured to select one of the stored plurality of relationships between volume and pressure from the memory and, based upon at least one selection criterion, select one of the stored plurality of relationships between impedance and volume, and estimate a pressure of an element of the cardiovascular system based on the stored data and the selected relationships. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22)
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23. A system comprising:
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means for storing a plurality of relationships between volume and pressure, the plurality of relationships comprising a relationship between volume and pressure in a vascular lumen; means for storing a plurality of relationships between impedance and volume; means for measuring an impedance between at least two electrodes implanted within a cardiovascular system of a patient; means for selecting one of the stored plurality of relationships between volume and pressure; means for selecting one of the stored plurality of relationships between impedance and volume based upon at least one selection criterion; and means for estimating a pressure of an element of the cardiovascular system based on the selected relationship between impedance and volume and based on the selected relationship between volume and pressure, wherein the relationship between the volume and the pressure comprises an elastance function derived from empirical data comprising historical data of the patient. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30, 31, 32)
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33. A non-transitory computer-readable storage medium comprising instructions that cause a processor to:
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measure an impedance between at least two electrodes implanted within a cardiovascular system of a patient; select one of a plurality of stored relationships between volume and pressure, the plurality of stored relationships comprising a relationship between volume and pressure in a vascular lumen; select one of a plurality of stored relationships between impedance and volume based upon at least one selection criterion; and estimate a pressure of an element of the cardiovascular system based on the relationship between the measured impedance and a volume of the element of the cardiovascular system and based on the selected relationship between the volume and the pressure, wherein the relationship between the volume and the pressure comprises an elastance function derived from empirical data comprising historical data of the patient.
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34. A method comprising:
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storing in a memory of an implantable medical device a plurality of relationships between volume and pressure, the plurality of relationships comprising a relationship between volume and pressure in a vascular lumen; storing in the memory a plurality of relationships between impedance and volume; measuring a complex impedance between at least two electrodes implanted within or proximate to a cardiovascular system of a patient; determining a reactive component of the measured complex impedance; enabling a control unit to select one of the stored plurality of relationships between volume and pressure and one of the stored plurality of relationships between impedance and volume based on at least one selection criterion; and providing, by the control unit, an indication of change in size of an element of the cardiovascular system based on the reactive component of the measured complex impedance and an indication of a change in pressure in the element of the cardiovascular system based on the selected relationship between volume and pressure. - View Dependent Claims (35, 36, 37)
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38. An implantable medical device comprising:
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a memory storing a plurality of relationships between volume and pressure, the plurality of relationships comprising a relationship between volume and pressure in a vascular lumen; the memory storing a plurality of relationships between impedance and volume; an impedance measurement module configured to measure a complex impedance between at least two electrodes implanted within or proximate to a cardiovascular system of a patient; and a processor configured to determine a reactive component of the measured complex impedance, and provide an indication of change in size of an element of the cardiovascular system based on the reactive component of the measured complex impedance, select one of the stored plurality of relationships between volume and pressure, select one of the stored plurality of relationships between impedance and volume based upon at least one selection criterion, and provide an indication of a change in pressure based on the change in size and the selected relationships. - View Dependent Claims (39, 40, 41)
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Specification