Heart Sound Monitoring for Preload Reserve Management
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Solution Overview
Problem
Current cardiac rhythm management devices face challenges in effectively monitoring and managing the inotropic state and preload of a heart, particularly in heart failure patients, as elevating preload beyond a critical point can lead to pulmonary congestion, and existing strategies may not adequately increase stroke volume.
Innovation Solution
The method involves monitoring S1 heart sounds and proxy variables for preload, using peak-to-peak differences in S3 or S4 heart sounds to determine inotropic state changes, and employing a system with a transducer and control circuit to communicate control signals for altering preload or inotropic state, thereby optimizing stroke volume while avoiding pulmonary congestion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If preload is elevated to increase stroke volume, then stroke volume is improved, but pulmonary congestion occurs when exceeding critical preload
Solution Approach 1:
The system continuously monitors heart sounds (S1, S2, S3, S4) and preload proxy variables to dynamically determine the ventricular operating point on the Frank Starling curve. This feedback mechanism allows real-time adjustment of preload and inotropic state to optimize stroke volume while preventing pulmonary congestion by identifying the optimal operating point before harmful effects occur.
Solution Approach 2:
The system alters physiological parameters (preload and inotropic state) based on detected heart sound characteristics and ventricular operating point. By dynamically changing these parameters according to the monitored cardiac state, the system achieves optimized stroke volume while avoiding the harmful effects of excessive preload.
2Productivity
If inotropic state is elevated to increase stroke volume, then stroke volume is improved, but the complexity of monitoring and management increases
Solution Approach 1:
The system uses the heart's own sound signals (S1, S2, S3, S4) as the monitoring medium, eliminating the need for complex external sensors or invasive measurements. The heart sounds themselves provide the data needed to determine ventricular operating point and guide therapeutic interventions, simplifying the monitoring infrastructure.
Solution Approach 2:
Heart sounds serve as an intermediary that indirectly reflects the ventricular operating point and inotropic state. Instead of directly measuring complex physiological parameters, the system uses heart sound analysis as a mediator to infer cardiac state and guide management decisions, reducing monitoring complexity.
3Productivity
If preload is elevated beyond critical point, then stroke volume increases, but the patient experiences shortness of breath due to pulmonary congestion
Solution Approach 1:
The system continuously monitors heart sounds and preload proxy variables to detect the approaching critical preload point before pulmonary congestion develops. By identifying the optimal ventricular operating point in advance, the system enables preemptive adjustment of preload to maintain adequate stroke volume while preventing the harmful effects of excessive preload and resulting shortness of breath.
Data Source
AI summary
A system and method for managing preload reserve and tracking the inotropic state of a patient's heart. The S1 heart sound is measured as a proxy for direct measurement of stroke volume. The S3 heart sound may be measured as a proxy for direct measurement of preload level. The S1-S3 pair yield a point on a Frank Starling type of curve, and reveal information regarding the patient's ventricular operating point and inotropic state. As an alternative, or in addition to, measurement of the S3 heart sound, the S4 heart sound may be measured or a direct pressure measurement may be made for the sake of determining the patient's preload level. The aforementioned measurements may be made by a cardiac rhythm management device, such as a pacemaker or implantable defibrillator.