Modified DVI Pacemaker Preventing Atrial Tachycardia
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Solution Overview
Problem
Conventional medical devices for treating cardiac arrhythmia, such as DVI and DVIR pacemakers, often induce atrial tachycardia due to improper pacing, especially when an atrial event occurs within or near an atrial refractory period, leading to unstable ventricular heart rates and severe tachycardia.
Innovation Solution
A medical device equipped with a microprocessor and digital/analog module that operates in a modified DVI mode, featuring a main control unit and time control unit, which sets a post-atrial non-pacing interval and adjusts pacing pulses based on sensed atrial events to prevent atrial tachycardia, using a post-atrial non-pacing interval to synchronize atrioventricular pacing and maintain stable heart rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If NCAP function is enabled in DDD mode to prevent atrial tachycardia, then atrial tachycardia is prevented, but ventricular heart rate stability deteriorates due to shortened PAV interval
Solution Approach 1:
The patent implements dynamic adjustment of the PAV interval based on the relationship between the NCAP interval and the lower frequency limit. The control unit shortens the PAV interval only when necessary (when NCAP interval exceeds the lower frequency limit threshold) and maintains it at normal duration otherwise, creating a dynamic adaptation that resolves the contradiction between preventing atrial tachycardia and maintaining ventricular heart rate stability
Solution Approach 2:
The patent changes the PAV interval parameter dynamically based on detected conditions. When an atrial event is sensed within the NCAP interval and the NCAP interval exceeds the lower frequency limit, the PAV interval is shortened to prevent atrial tachycardia. Otherwise, the PAV interval remains at its programmed duration, maintaining normal ventricular heart rate stability
2Stability of the object's composition
If PAV interval is shortened to maintain ventricular heart rate stability during NCAP, then ventricular heart rate stability is maintained, but risk of over-shortening and frequency limit violations increases
Solution Approach 1:
The patent employs feedback control by continuously monitoring the NCAP interval duration and comparing it against the lower frequency limit threshold. The control unit only shortens the PAV interval when the NCAP interval exceeds the threshold, and uses feedback from the lower frequency limit calculation to determine the appropriate shortened duration, ensuring frequency limit compliance while maintaining ventricular heart rate stability
3Device complexity
If conventional DVI mode is used without effective atrial sensing, then device complexity is reduced, but induced atrial tachycardia occurs due to improper pacing timing
Solution Approach 1:
The patent applies preliminary action by establishing a post-atrial non-pacing (PANP) interval upon sensing an atrial event, before any ventricular pacing decision is made. This preliminary timing mechanism prevents inappropriate ventricular pacing that could induce atrial tachycardia, while maintaining the simplicity of DVI mode without requiring continuous atrial sensing or complex algorithms
Data Source
AI summary
A medical device for treating cardiac arrhythmia includes a microprocessor. A MCU configures the medical device to operate in a modified DVI (R) mode in which: when receiving a signal indicating the sensing of an atrial event, the MCU sets a PANP interval and sends to a time control unit a signal; if a scheduled post-ventricular atrial escaping interval is to end at a time not within the PANP internal, the MCU sends respective signals to a pacing control/generation unit and the time control unit to dictate the pacing control/generation unit and control a second timing unit to use a PAVI as a next ventricular escape interval; and if the scheduled post-ventricular atrial escaping interval is to end within the PANP interval, the MCU sends a signal to the time control unit, controlling the second timing unit to use the PAVI as the next ventricular escape interval.