Implantable Medical Device Lead Fault Detection

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Solution Overview

Problem

Implantable medical devices (IMDs) face challenges in detecting lead faults, such as fractures or electrical failures, which can be transient and influenced by cardiac motion, making it difficult to predict and prevent actual failures using traditional impedance measurements taken only once daily or weekly.

Innovation Solution

The implementation of a system that measures lead impedance at multiple times during a cardiac cycle, specifically during systole and diastole, and uses a burst of measurements separated by 50 milliseconds to capture impedance artifacts due to heart motion, increasing the likelihood of detecting faults, and adjusts measurement frequency based on patient activity and environmental factors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If impedance measurements are taken only once daily or weekly, then device complexity and power consumption are reduced, but lead fault detection capability deteriorates

Engineering Contradiction:

Improvelead fault detection capabilityVSAvoidmeasurement frequency

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The system dynamically adjusts measurement frequency based on detected conditions. During normal operation, measurements are taken at lower frequency to conserve power. When a potential fault is detected or during high-risk periods, the system increases measurement frequency automatically, resolving the contradiction between detection capability and device complexity

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system performs preliminary impedance measurements at standard intervals to establish baseline values. When these preliminary measurements show deviations from expected ranges, the system triggers more frequent follow-up measurements, allowing early detection without continuously high measurement frequency

Inventive Principle:

Principle #10Preliminary action

2Reliability

If impedance measurements are taken at multiple times during cardiac cycle, then lead fault detection capability is improved, but power consumption increases

Engineering Contradiction:

Improvelead fault detection capabilityVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The system implements periodic impedance measurements synchronized with the cardiac cycle. Multiple measurements are taken at specific phases (systole and diastole) rather than continuously, capturing motion-related faults while limiting power consumption through rhythmic, phase-locked measurement intervals

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The system performs a burst of measurements at critical cardiac phases when fault detection is most valuable, rather than maintaining constant high-frequency measurement. This partial action approach focuses power consumption on the most diagnostically relevant time windows

Inventive Principle:

Principle #16Partial or excessive action

3Measurement precision

If measurements are separated by 50 milliseconds to capture impedance artifacts, then detection precision is improved, but measurement time increases

Engineering Contradiction:

Improvefault detection precisionVSAvoidmeasurement time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The system uses the first measurement in the burst as a preliminary reference value. Subsequent measurements at 50ms intervals are compared against this baseline to quickly identify deviations, reducing the time needed to process multiple measurements while maintaining detection precision

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system rapidly acquires multiple measurements in a compressed time window during critical cardiac phases, then quickly processes these results to determine lead status. This rushing through the measurement and decision process minimizes overall time loss while capturing transient faults

Inventive Principle:

Principle #21Skipping (Rushing through)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach enhances the detection of lead faults, including transient ones, by capturing impedance changes related to cardiac motion, thereby improving the reliability of electrostimulation therapy delivery and reducing the risk of therapy interruption.

Implementation Method 1

measuring at least two impedances of a first terminal combination including the therapy delivery terminal, the two impedances corresponding to at least two instances of excitation separated enough in time to capture an impedance artifact

Methodology Applied

Scientific EffectElectrical Impedance: Electrical Resistance

Data Source

PatentUS9014807B2Lead fault detection for implantable medical device

Publication Date: 2015.04.21 CARDIAC PACEMAKERS INC

AI summary

An implantable medical device can include a therapy circuit coupled to a therapy delivery terminal, the therapy circuit configured to generate a specified electrostimulation therapy for delivery to a tissue site via the therapy delivery terminal, and a measurement circuit for measuring at least two impedances of a first terminal combination including the therapy delivery terminal, the two impedances corresponding to at least two instances of excitation separated enough in time to capture an impedance artifact due at least in part to a motion of the heart, such as to determine an electrostimulation therapy lead status at least in part using the at least two impedances.