Paired Cardiac Pacing Inter-Pulse Interval Timing
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Solution Overview
Problem
Existing cardiac stimulation techniques, such as paired and coupled pacing, face challenges in safely enhancing cardiac performance without increasing the risk of fibrillation induction, particularly when stimulating near the vulnerable refractory period.
Innovation Solution
The implementation of an improved inter-pulse interval timing mechanism within implantable cardiac stimulation devices to ensure that the evoked response from a secondary pulse is wider than the primary pulse, thereby prolonging the refractory period and enhancing hemodynamic performance while minimizing the risk of arrhythmias, by optimizing the interval between pacing pulses to just outside the relative refractory period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a secondary pulse is delivered about 300 ms following a primary pacing pulse to enhance cardiac performance, then hemodynamic performance is improved, but the risk of fibrillation induction increases due to stimulation during the vulnerable refractory period
Solution Approach 1:
The patent adjusts the inter-pulse interval parameter to be greater than 300 ms, specifically timing the secondary pulse to occur after the vulnerable refractory period has ended. This parameter change allows the system to maintain hemodynamic enhancement benefits while avoiding the harmful arrhythmia induction risk by delivering the stimulus at a safer temporal point in the cardiac cycle.
Solution Approach 2:
The system determines the refractory period duration beforehand and uses this information to set the inter-pulse interval. By knowing when the vulnerable period ends, the pacing device can preliminarily plan the secondary pulse timing to occur after this critical window, thus preventing arrhythmia while maintaining therapeutic effect.
2Productivity
If the inter-pulse interval is shortened to increase pacing rate, then productivity is improved, but the evoked response width decreases reducing hemodynamic effectiveness
Solution Approach 1:
The patent establishes an optimal inter-pulse interval range that balances two competing parameters: pacing rate and evoked response width. By setting the interval to be greater than 300 ms but not excessively long, the system achieves a parameter optimization where the secondary pulse still elicits a sufficiently wide evoked response for hemodynamic effectiveness while maintaining an acceptable pacing rate for productivity.
Data Source
AI summary
A coupled/paired stimulus pulse is delivered to the heart at an inter-pulse interval following one of i) detection of an intrinsic depolarization or ii) delivery of a primary stimulus pulse. Capture resulting from the coupled/paired stimulus pulse is sensed for. In response to capture by a coupled/paired stimulus pulse, the inter-pulse interval is incrementally decreased by a first amount until there is no capture by a coupled/paired stimulus pulse. In response to no capture by a coupled/paired stimulus pulse, the inter-pulse interval is incrementally increased by a second amount greater than the first amount, until capture by a coupled/paired stimulus pulse is detected. Once capture is again detected, paired/coupled pacing is delivered at the inter-pulse interval which resulted in capture for a predetermined period of time or until loss of capture occurs.