Sub-threshold Anodal Stimulation for Heart Failure
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Solution Overview
Problem
Heart failure patients experience conduction delays in electrical impulses to the ventricles, leading to inefficient heart pumping, as existing pacemakers primarily use cathodal stimulation due to concerns about anodal current's higher threshold and potential for arrhythmogenesis, which limits the use of subthreshold anodal stimulation for improving cardiac contraction and battery longevity.
Innovation Solution
Implementing a system with sensors to detect weakening heart contractions and applying sub-threshold anodal waveforms to either the atria or ventricles, which can be adjusted based on feedback to enhance cardiac function without overstimulating the heart, thereby improving ventricular filling and overall heart efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If anodal current is used to stimulate the myocardium, then cardiac contraction is improved, but the stimulation threshold is higher and battery life is reduced
Solution Approach 1:
The patent applies subthreshold anodal conditioning pulses before the threshold stimulus to prepare the myocardium for more effective stimulation. This preliminary action modifies the membrane potential to facilitate subsequent depolarization, improving cardiac contraction while allowing the use of lower intensity main stimulation pulses that conserve battery energy.
Solution Approach 2:
The patent changes the temporal parameters of stimulation by introducing a conditioning phase before the main stimulus. The subthreshold anodal pulses are delivered at specific times (e.g., during the refractory period) to optimize the electrophysiological state of the myocardium, thereby reducing the energy required for effective cardiac stimulation.
2Strength
If anodal current is used to stimulate the myocardium, then cardiac contraction is improved, but the risk of arrhythmogenesis increases
Solution Approach 1:
The patent uses subthreshold anodal conditioning pulses that are below the threshold for direct depolarization. These partial actions prepare the tissue without causing the excessive depolarization that leads to arrhythmias, while still achieving the beneficial effect of improved cardiac contraction through modulation of membrane excitability.
Solution Approach 2:
By delivering subthreshold anodal conditioning pulses before the main stimulus, the patent prepares the myocardium in a controlled manner. This preliminary conditioning occurs during safe time windows (such as the refractory period) that minimize arrhythmia risk while optimizing the effectiveness of subsequent stimulation.
3Use of energy by moving object
If cathodal stimulation is used, then the stimulation threshold is lower and battery life is extended, but the cardiac contraction improvement is less effective
Solution Approach 1:
The patent merges cathodal threshold stimulation with subthreshold anodal conditioning pulses. The cathodal pulses provide the necessary depolarizing stimulus with low energy consumption, while the anodal conditioning pulses enhance myocardial responsiveness. This combination achieves effective cardiac contraction improvement while maintaining the energy efficiency of cathodal stimulation.
Solution Approach 2:
The patent modifies the stimulation protocol by adding a conditioning phase with subthreshold anodal pulses before the main cathodal stimulus. This parameter change optimizes the electrophysiological state of the myocardium, allowing for more effective cardiac contraction with the same or lower intensity main stimulus, thereby extending battery life.
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 approach enhances cardiac contraction speed and efficiency, reduces power consumption, and prolongs pacemaker battery life by using sub-threshold anodal stimulation to strengthen heart contractions while minimizing the risk of arrhythmogenesis.
Implementation Method 1
The effect of anodal current is to hyperpolarize the resting membrane. On sudden termination of the anodal pulse, the membrane potential returns towards resting level, overshoots to threshold, and a propagated response occurs.
Implementation Method 2
Cathodal current comprises electrical pulses of negative polarity. This type of current depolarizes the cell membrane by discharging the membrane capacitor, and directly reduces the membrane potential toward threshold level.
Data Source
AI summary
A rules engine acquires sensor data from sensors applied to the heart and determines whether an electrical waveform should be applied to the heart and, if so, the type of electrical waveform. A multi-phase cardiac stimulus generator generates waveforms in response to the rules engine. The electrical waveform is applied to one or more electrodes implanted in or on the heart.