Implantable Cardiac Device Wall Motion Assessment via Impedance
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Solution Overview
Problem
Current implantable medical devices for monitoring and treating cardiovascular conditions lack effective methods to assess cardiac wall motion, which is crucial for evaluating cardiac performance, progression of heart failure, and efficacy of therapies like CRT, and for detecting the hemodynamic significance of tachyarrhythmias.
Innovation Solution
An implantable medical device (IMD) uses impedance measurements through cardiac leads to assess cardiac wall motion by calculating changes in impedance during a cardiac cycle, employing a first electrode within the heart chamber and a second extra-cardiac electrode, such as a housing electrode or SVC coil, to determine values indicative of heart wall motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If implantable medical devices deliver electrical stimulation therapy and monitor physiological signals using conventional methods, then therapeutic functions are provided, but the ability to assess cardiac wall motion and contractility is insufficient
Solution Approach 1:
The patent enables implantable medical devices to perform multiple functions using existing components. The device uses its housing as an electrode and existing cardiac leads to measure impedance changes during cardiac cycles, allowing the same device to provide both therapy delivery and wall motion assessment without adding dedicated sensing hardware.
Solution Approach 2:
The device leverages its own structural components (housing and leads) to perform the measurement function. The housing serves dual purposes as both the device enclosure and an electrode for impedance measurement, while the cardiac leads already present in the device are utilized for signal acquisition, making the device self-sufficient for wall motion assessment.
2Reliability
If impedance measurements are taken to assess cardiac wall motion, then continuous monitoring of cardiac performance is enabled, but measurement accuracy during varying cardiac conditions may be compromised
Solution Approach 1:
The device performs impedance measurements at specific periodic intervals during the cardiac cycle, particularly during systole when wall motion occurs. By timing measurements to coincide with expected wall motion events, the device captures relevant physiological data while maintaining measurement reliability across varying heart rates and cardiac conditions.
Solution Approach 2:
The device uses the measured impedance changes to assess wall motion and can adjust therapy delivery based on these measurements. The feedback loop allows the device to adapt to varying cardiac conditions, improving both reliability and precision by responding to real-time physiological changes.
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 method allows for continuous monitoring of cardiac performance, assessment of therapy efficacy, and detection of hemodynamically significant tachyarrhythmias, enabling timely interventions and adjustments to cardiac resynchronization therapy.
Implementation Method 1
measuring an impedance of an electrical path that includes a portion of a heart wall a plurality of times during at least one portion of a cardiac cycle, the electrical path comprising a first electrode engaged to or within a wall of a chamber of a heart and a second electrode engaged to a housing of an implantable medical device (IMD)
Data Source
AI summary
In accordance with the techniques for heart monitoring described in this disclosure, an implantable medical device (IMD) may assess cardiac wall motion using impedance measurements through cardiac leads. As an example, the IMD may calculate an amount or rate of change in impedance due to the motion of a wall of the heart during at least a portion of one cardiac cycle, e.g., systole, in order to assess the strength of systolic contraction.