Subcutaneous Heart Failure Sensing with 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 do not provide a robust indication of acute decompensation between clinician visits, leading to potential adverse medical events such as hospitalization.
Innovation Solution
A subcutaneously implantable medical device measures tissue impedance (Z), tissue oxygen saturation (StO2), and pulse transit time (PTT) to determine a patient's heart failure status, transmitting this information to a remote computer for timely medical intervention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If clinical assessments of heart failure status are performed only during clinician visits, then medical expertise and resources are utilized effectively, but patients may experience acute decompensation and adverse events between visits
Solution Approach 1:
The implantable medical device autonomously monitors heart failure status parameters (tissue impedance, oxygen saturation, pulse transit time) and compares them against baseline values without requiring clinician intervention. The device self-determines whether parameter changes indicate acute decompensation, enabling continuous self-monitoring between visits and eliminating the time gap in surveillance.
Solution Approach 2:
The device continuously measures physiological parameters and provides feedback by comparing current values to baseline values. When changes exceed predetermined thresholds, the system generates alerts to both the patient and clinician, creating a closed-loop feedback system that enables timely intervention before acute decompensation occurs.
2Measurement precision
If multiple physiological parameters are measured to assess heart failure status, then diagnostic accuracy is improved, but device complexity and measurement requirements increase
Solution Approach 1:
The implantable medical device performs multiple functions using a single integrated system: it measures tissue impedance to assess congestion, monitors oxygen saturation to evaluate perfusion, and calculates pulse transit time to determine vascular resistance. All three heart failure status parameters are obtained from one device, eliminating the need for multiple separate measurement systems and reducing overall complexity.
Solution Approach 2:
The device combines three distinct measurement capabilities (impedance sensing, optical oxygen saturation detection, and pulse transit time calculation) into a single implantable unit. By merging these functions, the system achieves comprehensive heart failure monitoring without requiring multiple separate devices or complex coordination between independent systems.
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 monitoring of heart failure status outside clinical settings, allowing for proactive adjustment of therapy to prevent acute decompensation and reduce hospitalization risks.
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
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.