Fusion Pacing Enhancements for Cardiac Resynchronization
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Solution Overview
Problem
Current cardiac resynchronization pacing systems face challenges in effectively delivering fusion-based cardiac resynchronization therapy (CRT) to patients with cardiac conduction abnormalities, such as left or right bundle branch block, due to variations in patient physiology and conduction delays, leading to inefficient energy use and potential failure in therapy delivery.
Innovation Solution
The system automatically adjusts the AV interval by computing a Fusion-AV interval based on prior cardiac events, using a First-in, First-out (FIFO) memory buffer to evaluate intrinsic conduction intervals, and triggers a single ventricular pacing stimulus during a pre-excitation interval (PEI) to achieve mechanical synchrony between ventricles, minimizing pacing energy and extending the life of implantable devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a single ventricular pacing stimulus is delivered to achieve fusion-based CRT, then energy consumption is reduced and device life is extended, but the timing precision required to achieve effective resynchronization increases
Solution Approach 1:
The system performs preliminary evaluation of intrinsic conduction intervals using a FIFO memory buffer to store and analyze prior cardiac events (atrial events Ap/s and ventricular events Vs). This preliminary analysis allows the system to pre-calculate the optimal AV interval before delivering the pacing stimulus, ensuring precise timing without requiring complex real-time adjustments during stimulus delivery.
Solution Approach 2:
The system continuously monitors intrinsic conduction intervals by comparing atrial events (Ap/s) with ventricular events (Vs) and uses this feedback to dynamically adjust the AV interval. The FIFO buffer provides a history of conduction intervals that feeds back into the timing calculation, allowing the system to adapt to changing patient physiology and maintain optimal resynchronization timing.
2Device complexity
If the AV interval is fixed, then device operation is simplified, but the system cannot adapt to variations in patient physiology such as exercise or medication effects
Solution Approach 1:
The system implements a dynamic AV interval that automatically adjusts based on the patient's current physiologic state. By continuously evaluating intrinsic conduction intervals from recent cardiac events stored in the FIFO buffer, the system adapts the AV interval to accommodate variations caused by exercise, medications, or other physiologic changes, maintaining effective resynchronization without requiring manual reprogramming.
Solution Approach 2:
The system performs self-adjustment of the AV interval by automatically evaluating its own sensed cardiac events (atrial events Ap/s and ventricular events Vs) and computing the optimal timing based on intrinsic conduction properties. This self-service capability eliminates the need for external intervention or complex external programming while maintaining adaptability to physiologic changes.
3Reliability
If fusion-based CRT is delivered with imprecise timing, then the therapy fails to achieve resynchronization, but precise timing requires complex signal processing and conduction evaluation
Solution Approach 1:
The system performs preliminary evaluation of intrinsic conduction intervals by storing and analyzing pairs of atrial events (Ap/s) and ventricular events (Vs) in a FIFO memory buffer before delivering the pacing stimulus. This advance evaluation of conduction timing allows the system to pre-determine the optimal AV interval, ensuring reliable fusion-based CRT delivery without requiring complex real-time signal processing at the moment of stimulus delivery.
Data Source
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AI summary
The disclosure provides methods and apparatus of left ventricular pacing including automated adjustment of a atrio-ventricular (AV) pacing delay interval and intrinsic AV nodal conduction testing. It includes - upon expiration or reset of a programmable AV Evaluation Interval (AVEI) - performing the following: temporarily increasing a paced AV interval and a sensed AV interval and testing for adequate AV conduction and measuring an intrinsic atrio-ventricular (PR) interval for a right ventricular (RV) chamber. Thus, in the event that the AV conduction test reveals a physiologically acceptable intrinsic PR interval then storing the physiologically acceptable PR interval in a memory structure (e.g., a median P-R from one or more cardiac cycles). In the event that the AV conduction test reveals an AV conduction block condition or if unacceptably long PR intervals are revealed then a pacing mode-switch to a bi-ventricular (Bi-V) pacing mode occurs and the magnitude of the AVEI is increased.