Method for determining an ICD replacment time
First Claim
1. An implantable cardioverter/defibrillator (ICD) comprising:
- a battery;
a capacitor, chargeable by the battery;
voltage measuring means, capable of measuring the terminal voltage of the battery;
capacitor reforming means, for reforming the capacitor;
capacitor charge timing means;
recommended replacement time (RRT) signaling means, for issuing an RRT signal; and
control logic and timing circuitry having programmable memory, a battery status register and communication means whereby, the control logic and timing circuitry monitors the voltage measuring means and the charge timing means to control the battery status register and the issuance of an RRT signal from the RRT signaling means.
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Abstract
Improved methods of determining the recommended replacement time (RRT), and therefore extending the longevity, of implantable electronic medical devices, especially implantable cardioverter-defibrillators, pacemakers and similar devices which rely on a battery having at least a minimal charge in order for the device to perform its intended function and devices employing these methods are described. In one embodiment the improved method entails independent measurement of at least two different indicators of battery strength, at least one of which is affected by the battery'"'"'s internal impedance. In a preferred embodiment, terminal battery voltage and capacitor charge time are independently monitored. If the terminal battery voltage falls below a predetermined minimum threshold or the capacitor charge time is confirmed to exceed a predetermined maximum charge time, an RRT signal is issued. In an alternative embodiment, an RRT signal is also issued by the medical device when one indicator of battery strength, for example, battery terminal voltage, falls below a predetermined intermediate voltage but is above the minimum threshold voltage and a second indicator of battery strength, for example, capacitor charge time, exceeds its predetermined maximum threshold.
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Citations
15 Claims
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1. An implantable cardioverter/defibrillator (ICD) comprising:
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a battery; a capacitor, chargeable by the battery; voltage measuring means, capable of measuring the terminal voltage of the battery; capacitor reforming means, for reforming the capacitor; capacitor charge timing means; recommended replacement time (RRT) signaling means, for issuing an RRT signal; and control logic and timing circuitry having programmable memory, a battery status register and communication means whereby, the control logic and timing circuitry monitors the voltage measuring means and the charge timing means to control the battery status register and the issuance of an RRT signal from the RRT signaling means. - View Dependent Claims (2, 3, 4, 5)
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6. In an implantable cardioverter/defibrillator (ICD) having a battery, a capacitor, control logic and timing circuitry and a status registers an improved method of determining when to issue a recommended replacement time (RRT), the method comprising the steps of:
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a) periodically measuring a first indicator of battery strength; b) comparing the first measurement with a first predetermined threshold; c) issuing a first RRT signal in the event the first measurement is equal to or falls beyond the first predetermined threshold; d) comparing the first measurement to an intermediate threshold, in the event the first measurement is not equal to or beyond the first predetermined threshold; e) determining whether the status register is at a maximum count, in the event the first measurement is equal to or beyond the intermediate threshold; f) incrementally increasing the status register in the event the status register is not at the maximum count; g) measuring a second indicator of battery strength, which indicator is affected by the internal impedance of the battery, in the event the status register is at the maximum count; h) comparing the second measurement to a predetermined second threshold; and i) issuing a second RRT signal in the event the second measurement is equal to or beyond the predetermined second threshold. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14, 15)
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Specification