Leadless Pacemaker Capture Detection Using Endocardial Acceleration

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Solution Overview

Problem

Current ventricular capture test techniques for leadless cardiac pacemakers require significant digital processor energy consumption due to complex signal analysis and classification, which is undesirable for minimizing stimulation energy and reducing battery size in these devices.

Innovation Solution

A ventricular capture detection circuit that samples endocardiac acceleration signals during a predetermined time window after stimulation, calculates an average of absolute values, and compares this indicator to a dynamically determined threshold to determine capture presence, minimizing digital operations and power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If complex signal analysis and classification algorithms are used for ventricular capture detection, then measurement precision is improved, but use of energy increases significantly

Engineering Contradiction:

Improvecapture detection accuracyVSAvoiddigital processor energy consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent extracts only the essential feature needed for capture detection - the presence or absence of ventricular contraction - and detects it directly through simplified signal processing of endocardial acceleration signals, rather than performing complex full-signal analysis and classification. This extraction approach maintains detection accuracy while dramatically reducing computational energy consumption to a few hundred nanowatts.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

Instead of using complex algorithms to confirm capture presence, the patent inverts the approach by detecting the absence of contraction (no capture) through simplified signal features, and inferring capture presence by default. This inversion reduces computational complexity while maintaining measurement precision.

Inventive Principle:

Principle #13The other way round (Inversion)

2Volume of moving object

If battery capacity is reduced to minimize device volume, then volume of the capsule is reduced, but duration of action of stationary object decreases

Engineering Contradiction:

Improvecapsule volumeVSAvoidbattery lifespan

Core Design Contradiction:

Volume of moving objectVSDuration of action of stationary object

Solution Approach 1:

The patent changes the operational parameters of the capture detection system by replacing complex high-energy algorithms with simplified low-energy signal processing. This parameter change in computational complexity allows the device to maintain functionality with a smaller, lower-capacity battery, reducing capsule volume while preserving operational duration through energy efficiency rather than increased battery size.

Inventive Principle:

Principle #35Parameter changes

3Use of energy by moving object

If stimulation energy is reduced to minimum levels, then use of energy is improved, but reliability of capture may deteriorate

Engineering Contradiction:

Improvestimulation energyVSAvoidcapture reliability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent implements a feedback mechanism where the simplified capture detection system continuously monitors endocardial acceleration signals to determine whether each stimulation pulse successfully captured the ventricle. This real-time feedback allows the device to adjust stimulation energy dynamically - using minimum energy when capture is achieved and increasing energy only when capture is lost - thereby maintaining capture reliability while minimizing overall energy consumption.

Inventive Principle:

Principle #23Feedback

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 reduces energy consumption to a few hundred nanowatts, allowing for a 40-60% reduction in battery size while maintaining effective capture detection with improved noise immunity and reliability.

Implementation Method 1

integrating a microaccelerometer making it possible to measure the endocardiac acceleration

Methodology Applied

Scientific EffectAccelerometer: Accelerometer

Data Source

PatentEP3025758B1Active implantable medical device, in particular a leadless capsule, with cycle-to-cycle capture detection by analysing an endocardial acceleration signal

Publication Date: 2017.06.28 SORIN CRM

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AI summary

The device incorporates an endocardial acceleration (EA) sensor. The capture test circuit collects the sampled EA signal (102), and a windowing device extracts a limited series of EA measurements during a predetermined time window opened after delivery of a pacing pulse (100). An indicator (MEANABS), a function of the average of the absolute values of successive EA measurements in said series of EA measurements, is calculated at the end of the time window (104) and then compared (106) to a predetermined discrimination threshold (CapThreshold) to determine the presence (108) or absence (110) of a capture, depending on whether the indicator value is above or below this threshold. This indicator is very robust to noise and particularly computationally efficient, which allows for a significant reduction in the power consumption of the digital processor and therefore of the capsule.