Charge Balanced Cardiac Pacing via High Voltage ICD Circuitry
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Solution Overview
Problem
Extra-cardiovascular implantable cardioverter defibrillators (ICDs) face challenges in delivering cardiac pacing pulses without causing electrode corrosion and interference with cardiac signal sensing, particularly due to non-charge balanced pacing pulses.
Innovation Solution
The ICD system employs a high voltage therapy module to deliver charge balanced cardiac pacing pulses using extra-cardiovascular electrodes, which includes a sensing module, a high voltage therapy module, and a control module to detect the need for pacing and deliver balanced pulses by charging a capacitor to a pacing voltage amplitude and discharging it in a controlled manner to minimize corrosion and interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If non-charge balanced pacing pulses are delivered using extra-cardiovascular electrodes, then pacing function is achieved, but electrode corrosion and interference with cardiac signal sensing occur
Solution Approach 1:
The patent changes the electrical parameter of the pacing pulse from non-charge balanced to charge balanced configuration. This involves delivering a first pacing pulse with a first polarity followed by a second pacing pulse with opposite polarity, such that the total charge delivered is balanced. This parameter change resolves the contradiction by eliminating electrode corrosion and sensing interference while maintaining effective pacing function.
Solution Approach 2:
The patent implements periodic charge balanced pulsing where alternating polarity pulses are delivered in sequence. The first pacing pulse is followed by a second pacing pulse with opposite polarity, creating a periodic action that balances charge over time. This periodic charge balanced delivery method prevents cumulative electrode corrosion and reduces sensing artifacts.
2Object-generated harmful factors
If charge balanced pacing pulses are delivered using the high voltage therapy module, then electrode corrosion is reduced, but the complexity of the high voltage charging circuit and switching circuitry increases
Solution Approach 1:
The patent makes the high voltage therapy module multi-functional by enabling it to deliver both high voltage cardioversion/defibrillation shocks and charge balanced pacing pulses. The existing capacitor and switching circuitry are configured to serve dual purposes: charging to high voltage for shock delivery and charging to lower voltage for pacing pulse delivery. This universality reduces device complexity by avoiding the need for separate low voltage pacing circuitry.
Solution Approach 2:
The patent merges the pacing function with the existing high voltage therapy module infrastructure. The high voltage charging circuit and switching circuitry that were originally designed for shock delivery are combined with pacing pulse delivery capability. By merging these functions into a single integrated system, the patent avoids adding separate dedicated pacing circuitry, thus managing complexity while achieving charge balanced pacing.
3Adaptability or versatility
If the high voltage therapy module is used for both shocks and pacing pulses, then device versatility is improved, but the capacitor charging control becomes more complex
Solution Approach 1:
The patent implements dynamic capacitor charging control where the charging voltage is adjusted based on the required therapy type. For pacing pulses, the capacitor is charged to a first voltage level appropriate for low energy delivery, while for cardioversion/defibrillation shocks, the capacitor is charged to a higher second voltage level. This dynamic voltage adjustment enables a single capacitor to serve both functions with appropriate charging control, managing complexity through adaptive voltage management.
Solution Approach 2:
The patent uses parameter changes in capacitor charging voltage to distinguish between pacing and shock modes. The control circuitry adjusts the charging voltage parameter based on the detected need: lower voltage for pacing pulses and higher voltage for shocks. This parameter-based differentiation allows the same physical infrastructure to deliver different therapies with appropriate energy levels, achieving versatility while managing control complexity through voltage parameter adjustment.
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 reduces electrode corrosion and interference, ensuring effective and reliable cardiac pacing while maintaining the ability to deliver high voltage shocks for tachycardia or fibrillation termination.
Implementation Method 1
a capacitor chargeable to a shock voltage amplitude for delivering cardioversion/defibrillation shocks
Implementation Method 2
a high voltage charging circuit configured to charge the capacitor to the shock voltage amplitude
Implementation Method 3
switching circuitry configured to couple first capacitor to a pacing electrode vector selected from implantable extra-cardiovascular electrodes
Implementation Method 4
a sensing module configured to receive a cardiac electrical signal from a patient's heart
Data Source
AI summary
An extra-cardiovascular implantable cardioverter defibrillator (ICD) having a high voltage therapy module is configured to control a high voltage charging circuit to charge a capacitor to a pacing voltage amplitude to deliver charge balanced pacing pulses. The capacitor is chargeable to a shock voltage amplitude that is greater than the pacing voltage amplitude. The ICD is configured to enable switching circuitry of the high voltage therapy module to discharge the capacitor to deliver a first pulse having a first polarity and a leading voltage amplitude corresponding to the pacing voltage amplitude for pacing the patient's heart via a pacing electrode vector selected from extra-cardiovascular electrodes. The high voltage therapy module delivers a second pulse after the first pulse. The second pulse has a second polarity opposite the first polarity and balances the electrical charge delivered during the first pulse.