Implantable cardiac stimulating device incorporating high frequency low amplitude lead impedance measurement
First Claim
1. An implantable cardiac stimulation device enclosed in a conductive housing and adapted for use with at least one cardiac lead suitable for shocking a patient'"'"'s heart, the device further adapted to detect lead fractures that would prevent a high voltage shock to a patient'"'"'s heart, the device comprising:
- a current generator coupled to said lead and adapted to supply an impedance measuring current to the lead, said current being of a relatively low amplitude and a relatively high frequency;
a return in electrical communication with the current generator and the lead and forming thereby a current return path between the lead and the current generator; and
an impedance measuring circuit coupled to the lead and return such that upon the supply of the impedance measuring current to the lead the impedance measurement circuit measures the impedance between the lead and the return.
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Accused Products
Abstract
An implantable cardiac stimulating device incorporating high voltage leads for the delivery of cardioversion or defibrillation waveforms is provided. The implantable cardiac stimulating device incorporates a lead impedance measurement which measures the impedance of the high voltage lead using a high frequency, e.g., 20 KHz or higher, low amplitude, e.g., 500 microamps or lower, signal which results in a lead impedance measurement that has a high degree of correlation to the lead impedance that would occur when the high voltage defibrillation or cardioversion waveform is applied to the heart from the electrode. The implantable cardiac stimulating device is further configured to take corrective action upon the detection of a lead having a high or low impedance that suggests a broken, shorted or damaged lead.
103 Citations
39 Claims
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1. An implantable cardiac stimulation device enclosed in a conductive housing and adapted for use with at least one cardiac lead suitable for shocking a patient'"'"'s heart, the device further adapted to detect lead fractures that would prevent a high voltage shock to a patient'"'"'s heart, the device comprising:
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a current generator coupled to said lead and adapted to supply an impedance measuring current to the lead, said current being of a relatively low amplitude and a relatively high frequency;
a return in electrical communication with the current generator and the lead and forming thereby a current return path between the lead and the current generator; and
an impedance measuring circuit coupled to the lead and return such that upon the supply of the impedance measuring current to the lead the impedance measurement circuit measures the impedance between the lead and the return. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. In a cardiac stimulation device enclosed in an electrically conductive housing and configured for use with at least one cardiac lead suitable for shocking a patient'"'"'s heart and a current return, a method of determining the impedance of such lead to detect lead fractures that would prevent a high voltage shock to a patient'"'"'s heart, the method comprising the steps of:
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applying an impedance measuring current, having a relatively low amplitude and a relatively high frequency, to the lead and return;
measuring the resultant voltage across the lead and return; and
determining the lead impedance based upon the value of the impedance measuring current and the resultant voltage across the lead and return. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
comparing the lead impedance to a preselected maximum value and a preselected minimum value; and
taking corrective action when the lead impedance either exceeds the preselected maximum value or is less than the preselected minimum value.
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27. The method of claim 26 comprising the step of providing an annunciator signal when a lead impedance exceeds a predetermined maximum value or is less than a predetermined minimum value.
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28. An implantable cardiac stimulation device enclosed in a conductive housing and adapted for use with cardiac lead means, the device further adapted to measure the impedance of said lead means, the device comprising:
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means for supplying an impedance measuring current, having a relatively low amplitude and a relatively high frequency, to the lead means; and
means for determining the lead impedance based upon the supply of impedance measuring current to the lead means. - View Dependent Claims (29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39)
band pass filter means having a center frequency essentially equal to the frequency of the impedance measuring current for filtering the lead impedance signal and for providing thereby a band passed signal; and
demodulator means for demodulating the band passed signal for providing a parameter representative of the lead impedance.
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36. The device of claim 35 wherein the cardiac stimulation device further comprises:
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pulse generator means for delivering therapeutic electrical stimulation to a patient'"'"'s heart via the lead means; and
means for adjusting the electrical stimulation to said heart as a function of said parameter.
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37. The device of claim 35 further comprising means for disabling a respective lead, when said parameter corresponding to said respective lead, exceeds a preselected maximum value or is less than a preselected minimum value.
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38. The device of claim 28 wherein the supplying means supplies an impedance measuring current having a magnitude of no greater than 500 ua.
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39. The device of claim 28 wherein the supplying means supplies an impedance measuring current having a frequency in the range from 20 kHz to 50 kHz.
Specification