Implantable Device Ischemia Threshold Determination
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Solution Overview
Problem
Implantable pacemakers and defibrillators often pace patients with coronary artery disease beyond their ischemic threshold, leading to inadequate blood flow, as existing devices lack effective methods for determining and monitoring individual ischemia thresholds during rest periods.
Innovation Solution
A cardiac rhythm management device periodically determines the ischemic threshold by gradually increasing pacing rate until ischemia is detected or patient feedback is received, allowing for monitoring and adjustment of pacing rates to avoid ischemic zones and providing cardiovascular exercise benefits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If rate-responsive pacing is used to adjust pacing rate based on sensed activity, then the pacing rate can meet myocardial demand during exercise, but the pacing rate may exceed the ischemic threshold in patients with coronary artery disease
Solution Approach 1:
The device implements a feedback mechanism where ischemia detection triggers a response to reduce pacing rate. The pacemaker continuously monitors for ischemic conditions and automatically adjusts the pacing rate downward when ischemia is detected, creating a closed-loop control system that prevents pacing-induced ischemia while maintaining rate adaptability
Solution Approach 2:
The invention changes the pacing rate parameter dynamically based on detected ischemic conditions. When ischemia is detected, the system modifies the pacing rate from its activity-determined value to a lower safe value, thereby adapting the pacing parameters to prevent harmful effects
2Object-affected harmful factors
If ischemia detection devices are implemented to reduce pacing rate when ischemia is detected, then myocardial ischemia can be prevented, but the device complexity increases
Solution Approach 1:
The pacemaker device performs multiple functions: standard rate-responsive pacing, ischemia detection, and automatic pacing rate adjustment. By integrating these functions into a single device, the invention avoids the need for separate external monitoring equipment, thereby managing device complexity while providing comprehensive ischemia prevention
3Use of energy by moving object
If the pacing rate is increased to provide cardiovascular exercise benefits, then myocardial preconditioning is achieved, but the patient may experience ischemic symptoms
Solution Approach 1:
The system uses feedback from ischemia detection to control the pacing rate during exercise simulation. When ischemic symptoms are detected during rate increase, the feedback mechanism triggers a reduction in pacing rate, allowing the system to stop before severe ischemia occurs while still providing beneficial myocardial preconditioning
Data Source
AI summary
An implantable medical device (IMD) performs periodic testing of a patient to determine ischemia threshold information. At selected times while the patient is at rest, the IMD increases the pacing rate over time until it receives feedback either from the patient or from an ischemia sensor. The IMD determines the threshold based upon the pacing rate at the time when the feedback was received. The threshold information can be used to adjust the upper pacing rate that can be used during rate adaptive pacing, to determine the effects of drug therapy, and to provide a general indication of the state of coronary artery disease in the patient. The periodic increase of pacing rate to the ischemic zone also provides a preconditioning of the myocardium to allow the patient greater exercise benefit without angina.