Extra-Cardiovascular ICD ATP Timing Compensation for Sensing Delay
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Solution Overview
Problem
Existing implantable medical devices (IMDs) face challenges in effectively delivering anti-tachycardia pacing (ATP) pulses to the myocardium using extra-cardiovascular electrodes, as the timing of the leading ATP pulse may not align with the physiological refractory period due to the distance and time difference between sensing and actual myocardial depolarization.
Innovation Solution
An extra-cardiovascular implantable cardioverter defibrillator (ICD) system that uses an electrical sensing circuit to detect tachycardia, determines a tachycardia cycle length, sets an extended ATP interval, and delivers ATP pulses via extra-cardiovascular pacing electrodes, ensuring the pulses are timed to capture the myocardium outside the refractory period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If ATP pulses are delivered using extra-cardiovascular electrodes, then the device can treat tachycardia without transvenous leads, but the timing of the leading ATP pulse may not align with the physiological refractory period due to distance and time difference between sensing and actual myocardial depolarization
Solution Approach 1:
The system pre-calculates and stores a time difference value representing the delay between sensing the cardiac event at extra-cardiovascular electrodes and the actual myocardial depolarization. When delivering ATP pulses, this pre-determined time difference is added to the basic ATP interval to establish an extended ATP interval, ensuring the leading pulse is delivered at the correct physiological moment despite the sensing delay
Solution Approach 2:
The system modifies the ATP interval parameter by extending it with an additional time component. The extended ATP interval equals the basic ATP interval plus the time difference between sensing and actual depolarization. This parameter adjustment compensates for the delayed sensing inherent in extra-cardiovascular electrode placement, aligning pulse delivery with the refractory period
2Measurement precision
If the ATP interval is extended to account for sensing delay, then the leading pulse timing is more accurate, but the overall ATP delivery timing is delayed
Solution Approach 1:
The time difference value is pre-calculated and stored in memory before ATP delivery is needed. This preliminary determination of the sensing delay allows the system to proactively adjust the ATP interval without adding computational delay during the critical tachycardia treatment moment
Solution Approach 2:
The system changes the ATP interval parameter from a fixed basic value to a dynamically extended value that incorporates the sensing delay. This parameter transformation ensures timing accuracy while the pre-computed nature of the extension minimizes any additional time loss
Data Source
AI summary
An extra-cardiovascular implantable cardioverter defibrillator (ICD) system receives a cardiac electrical signal by an electrical sensing circuit via an extra-cardiovascular sensing electrode vector and senses cardiac events from the cardiac electrical signal. The ICD system detects tachycardia from the cardiac electrical signal and determines a tachycardia cycle length from the cardiac electrical signal. The ICD system determines an ATP interval based on the tachycardia cycle length and sets an extended ATP interval that is longer than the ATP interval. The ICD delivers ATP pulses to a patient's heart via an extra-cardiovascular pacing electrode vector different than the sensing electrode vector. The ATP pulses include a leading ATP pulse delivered at the extended ATP interval after a cardiac event is sensed from the cardiac electrical signal and a second ATP pulse delivered at the ATP interval following the leading ATP pulse.