Implantable Device Heart Rate Variability Monitoring
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Solution Overview
Problem
Conventional methods for determining heart rate variability in implantable medical devices are less accurate, leading to incorrect assessments of cardiac sympathetic reserve, which can result in patients not receiving beneficial cardiac therapies.
Innovation Solution
An implantable device that uses accurate assessments of basal autonomic tone to monitor heart rate variability over extended periods, excluding periods of activity to provide a more precise measurement, thereby enhancing diagnostic utility and potentially improving therapy delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If conventional methods measure heart rate variability by computing standard deviation of median atrial interval values every five minutes over 24 hours, then continuous monitoring is achieved, but measurement precision deteriorates due to inclusion of activity periods causing underestimation
Solution Approach 1:
The patent segments the 24-hour monitoring period into distinct activity and rest periods using an activity sensor. By dividing the continuous monitoring into these segments, the device can selectively include only rest period data in heart rate variability calculations, thereby eliminating the distortion caused by activity periods while maintaining continuous monitoring capability.
Solution Approach 2:
The patent performs preliminary classification of time periods as either activity or rest periods before conducting heart rate variability calculations. The activity sensor continuously monitors and tags each time period in advance, so that when HRV computation is performed, the device already has pre-identified rest period segments to use, ensuring accurate measurements without including activity-contaminated data.
2Quantity of substance
If activity periods are included in heart rate variability measurement, then comprehensive data collection is achieved, but diagnostic accuracy deteriorates due to underestimation of basal autonomic tone
Solution Approach 1:
The patent extracts and separates activity period data from the overall heart rate variability calculation. By using the activity sensor to identify and remove activity-contaminated segments, the device extracts only the pure rest period data needed for accurate basal autonomic tone assessment, while still collecting comprehensive data during activity periods for other diagnostic purposes.
3Reliability
If standard deviation of median atrial interval values is computed over extended periods, then statistical reliability is improved, but measurement accuracy deteriorates due to confounding effects of varying activity levels
Solution Approach 1:
The patent applies local quality by computing heart rate variability statistics separately for rest periods only, rather than uniformly across all time periods. The activity sensor enables the device to apply different computational rules to different time segments: rest period data is used for HRV calculations to ensure accuracy, while activity period data is collected separately for other purposes, thus maintaining statistical reliability without contamination.
Data Source
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AI summary
An implantable monitoring device is disclosed for monitoring a patient's heart rate variability over time. The device includes a cardiac electrogram amplifier, a sensing electrode coupled to an input of the amplifier, timing circuitry, processing circuitry and a memory. The timing circuitry defines successive shorter time periods during each monitoring period. The processing circuitry relies upon electrogram activity that occurs during rest periods that extend as long as T1, all of which is stored into memory. Active periods are not considered as part of the heart rate variability calculation. The processing circuitry calculates median intervals between depolarizations of the patient's heart sensed by the amplifier during the shorter time periods and calculates a standard deviation of the median intervals during T2, a longer monitoring period.