Method for determining an ICD replacement time
First Claim
1. In an implantable cardioverter/defibrillator (ICD) having a battery, a capacitor and control logic and timing circuitry, an improved method of determining when to issue a recommended replacement time (RRT) signal corresponding to a recommended time to replace the ICD, the method comprising:
- a) periodically measuring a first indicator of battery strength;
b) comparing the first measurement with a first predetermined threshold;
c) issuing an RRT signal in the event the first measurement is equal to or falls beyond the first predetermined threshold;
d) periodically measuring a second indicator of battery strength, which indicator is affected by the internal impedance of the battery and wherein the period between measurements is selected independently of the period between measurements of the first indicator;
d) comparing the second measurement with a second predetermined threshold; and
f) issuing an RRT signal in the event the second measurement is equal to or falls beyond the second predetermined threshold.
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Accused Products
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.
99 Citations
30 Claims
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1. In an implantable cardioverter/defibrillator (ICD) having a battery, a capacitor and control logic and timing circuitry, an improved method of determining when to issue a recommended replacement time (RRT) signal corresponding to a recommended time to replace the ICD, the method comprising:
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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 an RRT signal in the event the first measurement is equal to or falls beyond the first predetermined threshold; d) periodically measuring a second indicator of battery strength, which indicator is affected by the internal impedance of the battery and wherein the period between measurements is selected independently of the period between measurements of the first indicator; d) comparing the second measurement with a second predetermined threshold; and f) issuing an RRT signal in the event the second measurement is equal to or falls beyond the second predetermined threshold. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. In an implantable cardioverter/defibrillator (ICD) having a battery with an internal impedance and a voltage measurable across a pair of battery terminals, an improved method of determining when to issue a recommended replacement time (RRT) signal corresponding to a recommended time to replace the ICD, the method comprising the steps of:
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periodically and independently measuring two indicators of battery strength, wherein at least one of the indicators is affected by the internal impedance of the battery; defining a predetermined threshold for each of the two battery strength indicators; and issuing an RRT signal when either one of the two battery strength indicators is equal to or beyond the respective predetermined threshold. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23)
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24. An implantable cardioverter/defibrillator (ICD) comprising:
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a battery having a voltage and an impedance measurable across a pair of terminals; a capacitor coupled to and chargeable by the battery; voltage measuring means, coupled to the battery, for measuring the terminal voltage of the battery; capacitor reforming means for reforming the capacitor; capacitor charge timing means, responsive to the capacitor reforming means, for measuring a charge time of the capacitor during capacitor reformation; and control means, coupled to the voltage measuring means and the capacitor charge timing means, for independently detecting when one of the battery terminal voltage and the capacitor charge time exceed a respective predetermined threshold and for issuing a recommended replacement time (RRT) signal in response thereto, the RRT signal corresponding to a recommended time to replace the ICD. - View Dependent Claims (25, 26, 27, 28, 29, 30)
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Specification