Implantable Heart Failure Sensing Using Impedance, StO2, and PTT
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Solution Overview
Problem
Current methods for assessing heart failure status in patients are limited to clinical settings and require medical expertise, making it difficult to monitor and predict acute decompensation between clinician visits, which can lead to adverse events such as hospitalization.
Innovation Solution
A subcutaneously implantable medical device with electrodes and optical sensors monitors tissue impedance (Z), tissue oxygen saturation (StO2), and pulse transit time (PTT) to assess cardiac function, comparing these values to baselines to determine a heart failure status and transmit instructions for medical intervention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If clinical assessment methods are used to monitor heart failure status, then measurement precision is improved, but device complexity and ease of operation worsen due to requiring medical expertise and clinical settings
Solution Approach 1:
The implantable medical device automatically performs heart failure status assessments using physiological signals (impedance, oxygen saturation, pulse transit time) without requiring external medical expertise. The device self-monitors and self-evaluates by comparing current values to baseline values, enabling patients to receive continuous monitoring at home without clinician involvement.
Solution Approach 2:
The patent replaces manual clinical assessment methods with an automated electronic system that uses physiological signal processing. Instead of clinicians physically examining patients, the device uses electrodes and optical sensors to detect and analyze physiological parameters, substituting mechanical/ manual assessment with electronic measurement and automated analysis.
2Productivity
If continuous monitoring is implemented outside clinical settings, then productivity is improved by enabling proactive therapy adjustments, but device complexity increases due to multiple sensors and processing requirements
Solution Approach 1:
The patent combines multiple sensing functions (impedance sensing, oxygen saturation measurement, pulse transit time detection) into a single implantable device. By merging these different measurement capabilities into one integrated system, the device achieves continuous comprehensive monitoring without requiring multiple separate devices or complex external equipment.
Solution Approach 2:
The implantable medical device performs multiple functions: it monitors impedance, oxygen saturation, and pulse transit time; compares these to baseline values; determines heart failure status; and triggers alerts. This multi-functional approach allows a single device to provide comprehensive heart failure management rather than requiring specialized devices for each measurement.
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 continuous, accurate monitoring of heart failure status outside clinical settings, allowing for proactive adjustments to therapy and reducing the risk of acute decompensation and hospitalization.
Implementation Method 1
determining a current tissue oxygen saturation value of the patient based on a signal received from the at least one optical sensor
Implementation Method 2
determining a current tissue impedance value of the patient based on a subcutaneous tissue impedance signal received from a first at least two of the plurality of electrodes
Implementation Method 3
determining a current pulse transit time value of the patient based on a cardiac electrogram signal received from a second at least two of the plurality of electrodes and at least one of the signal received from the at least one optical sensor and the subcutaneous tissue impedance signal
Data Source
AI summary
In some examples, determining a heart failure status includes using an implantable medical device configured for subcutaneous implantation and comprising a plurality of electrodes and an optical sensor. Processing circuitry of a system comprising the device may determine, for a patient, a current tissue oxygen saturation value based on a signal received from the at least one optical sensor, a current tissue impedance value based on a subcutaneous tissue impedance signal received from the electrodes, and a current pulse transit time value based on a cardiac electrogram signal received from the electrodes and at least one of the signal received from the optical sensor and the subcutaneous tissue impedance signal. The processing circuitry may further compare the current tissue oxygen saturation value, current tissue impedance value, and current pulse transit time value to corresponding baseline values, and determine the heart failure status of the patient based on the comparison.