Implantable Pacemaker Atrial Stimulation During Ventricular Refractory Period
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Solution Overview
Problem
Current treatments for tachycardia, heart failure, and hypertension lack effective methods to reduce heart rate and blood pressure without inducing arrhythmias, as previous approaches using paired and coupled pacing pulses were abandoned due to tachyarrhythmia risks.
Innovation Solution
The solution involves exciting the atria, sino-atrial node, and/or AV node during the ventricular refractory period, creating a stimulus time window to delay ventricular contraction and reduce heart rate and blood pressure by up to 50%, using typical or burst pacing pulses with proper timing to avoid arrhythmias.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If paired and coupled pacing pulses are applied to slow heart rate and increase cardiac output, then cardiac performance is improved, but tachyarrhythmia is triggered in susceptible hearts
Solution Approach 1:
The patent applies preliminary action by delivering a first pacing pulse that initiates a refractory period in the ventricular myocardium, then delivers a second pacing pulse during this refractory period. The first pulse prepares the cardiac tissue by creating a protective refractory state, allowing the second pulse to slow heart rate without triggering tachyarrhythmia. This sequential timing of pulses resolves the contradiction by using the refractory period as a protective mechanism.
Solution Approach 2:
The patent employs periodic action by delivering pacing pulses at specific intervals that exploit the cardiac refractory period. The inter-pulse interval is carefully controlled to fall within the refractory period created by the first pulse, creating a periodic stimulation pattern that slows heart rate while avoiding the harmful effect of tachyarrhythmia. This periodic timing strategy allows beneficial cardiac output enhancement without triggering arrhythmias.
2Strength
If high energy pacing pulses are used to achieve potentiation effect, then contractile force is increased, but risk of triggering tachyarrhythmia increases
Solution Approach 1:
The patent uses preliminary action by delivering a conditioning first pulse that creates a refractory period and prepares the myocardium for enhanced contractility. This first pulse initiates post-extrasystolic potentiation (PESP) effects, and the second pulse delivered during the refractory period amplifies the contractile force without triggering tachyarrhythmia. The sequential timing allows high-energy pulsing for strength enhancement while the refractory period protects against arrhythmia.
Solution Approach 2:
The patent applies dynamics by adjusting the timing and energy of pacing pulses based on the dynamic refractory period of the cardiac tissue. The inter-pulse interval is dynamically set to fall within the refractory period, and pulse energies are optimized to produce PESP effects. This dynamic adjustment of pacing parameters allows the system to maximize contractile force while adapting to the changing electrical state of the myocardium, preventing tachyarrhythmia induction.
3Productivity
If closely timed paired and coupled pacing pulses are applied, then heart rate is slowed and cardiac output increases, but the treatment becomes complex and difficult to control
Solution Approach 1:
The patent incorporates feedback by sensing cardiac electrical activity (P-waves or R-waves) and using this information to trigger coupled pacing pulses. The device monitors the cardiac cycle and delivers the second pacing pulse at a predetermined interval following a sensed event, ensuring the pulse falls within the refractory period. This feedback mechanism simplifies control by automatically adjusting pulse timing based on real-time cardiac activity, reducing the complexity of manual programming while maintaining therapeutic effectiveness.
Solution Approach 2:
The patent applies parameter changes by programmably setting the coupling interval as a fraction of the sensed cardiac cycle length (e.g., 40-80% of the R-R or P-P interval). This parameter adjustment allows the device to adapt to varying heart rates and maintain optimal timing within the refractory period across different physiological conditions. By expressing the coupling interval as a percentage rather than a fixed value, the system simplifies control while achieving consistent therapeutic effects across a range of heart rates.
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 effectively reduces ventricular rate and blood pressure, allowing for titration of the effect to achieve desired reductions in heart rate and blood pressure without triggering arrhythmias, providing a safer and more controlled treatment option.
Implementation Method 1
an implantable pacemaker for stimulating a heart of a patient... delivers a stimulation pulse to at least one of the atria, the sino-atrial node, and the AV node
Data Source
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AI summary
An apparatus for reducing a patient's heart rate or blood pressure. The apparatus provides stimulation to the patient's atrial and/or nodal tissue within the associated refractory period of the ventricle but outside of an associated refractory period of the stimulated atrial an/or nodal tissue, responsive to detecting an occurrence of a ventricular depolarization following a preceding atrial depolarization. The apparatus may define a time window following the ventricular depolarization, following the atrial depolarization or determined based upon the timing of both the atrial and ventricular depolarizations. The stimulus may be delivered during or on expiration of the defined time window. The duration of the time window may be pre-set or determined based upon measurements of the patient's refractory periods.