Implantable Device Hemodynamic Index Determination
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Solution Overview
Problem
Existing cardiac pacemaker technologies lack the ability to effectively measure long-term evolution of cardiac flow and hemodynamic state, making it difficult to diagnose cardiac insufficiency and optimize stimulation parameters.
Innovation Solution
A device with means to determine an average hemodynamic index by measuring intracardiac impedance, processing signals to evaluate blood volume ejected during systole, and calculating this index over multiple cardiac cycles, under standardized conditions, using transvalvular impedance measurements and sensors to ensure accurate data collection and processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If transvalvular impedance measurement is performed to evaluate cardiac flow, then measurement precision is improved, but device complexity increases due to multiple electrode configurations
Solution Approach 1:
The implantable device integrates multiple functions including impedance measurement, cardiac stimulation, and hemodynamic monitoring within a single device architecture. The same electrodes used for cardiac pacing are also utilized for impedance measurements, eliminating the need for separate dedicated measurement electrodes and reducing overall device complexity while maintaining measurement precision
2Adaptability or versatility
If impedance measurements are taken under varying physiological conditions, then adaptability is improved, but measurement precision deteriorates due to inconsistent baseline conditions
Solution Approach 1:
The device incorporates feedback mechanisms that continuously monitor physiological parameters such as heart rate, respiratory rate, and activity level. Based on this feedback, the device dynamically adjusts measurement timing and parameters to ensure measurements are taken under standardized physiological conditions, thereby maintaining measurement precision while adapting to different patient states
Solution Approach 2:
The device performs preliminary assessments of physiological conditions before conducting impedance measurements. It evaluates factors such as recent patient activity, respiratory phase, and cardiac cycle timing, and only proceeds with measurements when conditions meet predefined criteria for consistency and reliability
3Loss of information
If frequent impedance measurements are performed to track long-term cardiac flow evolution, then information completeness is improved, but energy consumption increases
Solution Approach 1:
The device implements periodic impedance measurements at predetermined time intervals (e.g., daily, weekly, or monthly) rather than continuous measurements. This periodic sampling approach captures the long-term evolution of cardiac flow and detects trends in cardiac insufficiency while significantly reducing energy consumption compared to continuous monitoring
Solution Approach 2:
The device performs impedance measurements only during specific cardiac cycles that meet predefined quality criteria, rather than attempting to measure every cycle. This selective measurement approach ensures sufficient data quality for tracking long-term trends while minimizing the total number of measurements and associated energy consumption
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
Enables early diagnosis of cardiac insufficiency and optimization of stimulation parameters by providing a representative index of cardiac flow evolution, allowing for comparison of stimulated and non-stimulated modes to assess the effectiveness of cardiac activity.
Implementation Method 1
measuring the bio transvalvular impedance (i.e., the impedance between the atrium and the ventricle located on the same side of the heart) by a tripolar configuration, with injection of a current pulse between an atrial site and a ventricular site, and the collection (detection) of a differential potential
Data Source
AI summary
An active implantable medical device such as a cardiac pacemaker, defibrillator, cardiovertor and/or multisite device that is able to determine and average a hemodynamic index parameter. The intracardiac impedance signal is correlated to the instantaneous blood flow, and is used to determine periodically an average hemodynamic index (Dave) evaluated over several cardiac cycles under certain preset measurement conditions. For example, the preset conditions include checking that the state of the patient and of the device satisfies, the criteria (stages 12-20) defining predetermined measurement conditions, and inhibiting the determination of the aforesaid hemodynamic index if these criteria are not satisfied. A plurality of samples (Zij) of the measured impedance signal are collected over a length of time (Ti) of the systole of one cardiac cycle. Using the aforesaid samples, a value (Di) representative of the blood volume ejected throughout this systole is determined by integrating the samples over the time period. Then, average hemodynamic index (Dave) is calculated from a plurality of such integrated sample values successively determined over a plurality (N2) of cardiac cycles.