Multi-sensor Right Ventricular Electrode for Cardiac Rate Adaptive Pacing
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Solution Overview
Problem
Existing cardiac pacemakers relying on non-closed loop motion sensors struggle to accurately adjust heart rhythms in response to metabolic changes such as mood and mental activities, leading to discomfort and inefficiencies, while venous blood oxygen saturation measurements are influenced by various factors and have slow response times, and fibrous tissue growth can obscure optical sensors.
Innovation Solution
A multi-sensor composite right ventricular electrode equipped with a PPG sensor, temperature sensor, and impedance sensor that cross-compares blood oxygen saturation, temperature, and impedance information to provide a more accurate, rapid, and stable CRAP (Cardiac Rate Adaptive Pacing) system, dynamically adjusting LED driving current based on tissue thickness and temperature to minimize photothermic stimulation and extend sensor life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single-wavelength or dual-wavelength PPG sensor is used to measure blood oxygen saturation, then the pacemaker can perform closed-loop control for rate adaptive pacing, but the measurement is influenced by various uncertain factors (oxygen consumption changes, cardiac output fluctuations, hemoglobin concentration changes, arterial blood oxygen saturation changes) resulting in measurement difficulties and slow response time
Solution Approach 1:
The patent combines multiple sensing modalities (PPG, temperature, impedance) into a single integrated sensor system. The PPG sensor uses multiple wavelengths (red and infrared LEDs) to measure blood oxygen saturation, while simultaneously measuring temperature and impedance at the same site. This merging of functions allows cross-validation of metabolic changes and compensates for the slow response of blood oxygen saturation by incorporating faster-responsive temperature and impedance measurements.
Solution Approach 2:
The patent introduces temperature and impedance measurements as intermediary parameters that respond more rapidly to metabolic changes than blood oxygen saturation alone. These intermediary measurements provide early detection of metabolic changes, allowing the system to anticipate and respond faster to physiological changes while the slower blood oxygen saturation measurement provides confirmatory data.
2Reliability
If the PPG sensor is placed in the right ventricular cavity to measure blood oxygen saturation, then closed-loop CRAP can be achieved, but fibrous tissue wrapped around the electrode gradually thickens with implantation time, eventually obscuring the optical window and invalidating the PPG sensor
Solution Approach 1:
The patent implements feedback by continuously monitoring temperature and impedance measurements alongside PPG signals. Changes in temperature and impedance can indicate early signs of fibrous tissue encapsulation or changes in the local tissue environment. This feedback allows the system to detect sensor degradation before complete obscuration occurs and can trigger alerts or adjustments to maintain reliable CRAP control throughout the sensor's operational lifespan.
Solution Approach 2:
The patent monitors changes in multiple parameters (blood oxygen saturation, temperature, impedance) over time to detect the progressive effect of fibrous tissue encapsulation. By tracking parameter drift and signal quality degradation across these multiple measurements, the system can identify when the optical window is becoming obscured and adjust or alert before complete sensor invalidation, extending the effective operational lifespan.
3Adaptability or versatility
If non-closed loop motion sensors are used for rate adaptive pacing, then the device can respond to physical motion, but the sensors are sensitive to motions yet not sensitive to changes in non-motion metabolisms such as mood and mental activities, causing discomfort
Solution Approach 1:
The patent creates a universal sensing system that can detect multiple types of physiological changes through a single integrated platform. The PPG sensor detects blood oxygen saturation changes, the temperature sensor detects thermal changes, and the impedance sensor detects electrical property changes - all at the same right ventricular site. This multi-functionality allows the system to respond to both motion-induced changes and metabolism-induced changes (including mood and mental activities) with a single sensor system, eliminating the limitation of motion-only sensors.
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
The multi-sensor system improves the accuracy and speed of heart rhythm adjustments by cross-comparing blood oxygen saturation with temperature and impedance data, reducing the influence of other physiological processes and extending the lifespan of the PPG sensor by dynamically adjusting LED current and preventing tissue growth.
Implementation Method 1
These electrodes usually detect the blood oxygen saturation of the right ventricle blood with a photoplethysmography (PPG) sensor
Implementation Method 2
A head of the electrode is simultaneously equipped with a PPG sensor, a temperature sensor and an impedance sensor
Implementation Method 3
A head of the electrode is simultaneously equipped with a PPG sensor, a temperature sensor and an impedance sensor
Data Source
AI summary
Provided is an accurate, fast and long-term stable fused CRAP. The electrode includes a positioning anchor, a silicone catheter, a sensor compartment and a connecting wire. The method monitors physiological information such as blood PPG, blood oxygen saturation, temperature and impedance of blood in the right ventricular cavity, and monitors blood temperature information, which is also a slowly changing metabolic rate, to provide cross-comparison with blood oxygen saturation information, improving monitoring accuracy of blood oxygen saturation. The rapidly changing right ventricular apical impedance information is monitored to improve rapid response ability of CRAP. The LEDs driving current is dynamically adjusted by monitoring the internal temperature of the PPG sensor and the impedance change of the attached biological tissue, which indirectly reflects thickness change of the attached biological tissue, thereby delaying the failure time of the PPG sensor.