ICD Morphology Analysis for Monomorphic VT Shock Energy
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Solution Overview
Problem
Implantable cardioverter defibrillators (ICDs) face challenges in accurately discriminating between monomorphic and polymorphic ventricular tachycardia (VT) to deliver appropriate shock energy, often using high energy for polymorphic VT due to unreliable rate-based discrimination, leading to excessive battery consumption and patient discomfort.
Innovation Solution
The ICD employs morphological analysis of the electrocardiogram (ECG) waveforms during capacitor charging to differentiate between monomorphic and polymorphic VT, terminating charging early for monomorphic VT to deliver a lower energy shock synchronized with an R-wave, while completing charging for polymorphic VT to deliver the programmed shock energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high energy shock therapy is delivered for all detected VT, then reliability of arrhythmia termination is improved, but use of energy by moving object deteriorates
Solution Approach 1:
The system changes the energy parameter of shock therapy based on VT morphology classification. Monomorphic VT receives lower energy shocks while polymorphic VT receives full programmed energy shocks, optimizing the balance between termination reliability and energy conservation.
Solution Approach 2:
Different shock energy levels are applied to different types of VT based on their morphological characteristics. The system identifies monomorphic versus polymorphic VT and delivers appropriately differentiated therapy, avoiding unnecessary high energy shocks for monomorphic cases.
2Measurement precision
If morphology analysis is performed during capacitor charging, then measurement precision of VT type is improved, but device complexity increases
Solution Approach 1:
The morphology analysis is performed preliminarily during the capacitor charging process rather than after therapy delivery. This allows the system to classify VT type in advance and determine shock energy requirements before the charging completes, optimizing both precision and timing.
Solution Approach 2:
The morphology analysis continues throughout the capacitor charging process, utilizing the charging time to perform discrimination. This continuous analysis allows the system to make real-time decisions about shock energy delivery without adding significant complexity to the detection algorithm.
3Loss of time
If early shock delivery is implemented for monomorphic VT, then loss of time is reduced, but use of energy by moving object deteriorates
Solution Approach 1:
The system changes shock energy parameters based on VT morphology detected during capacitor charging. Monomorphic VT triggers early shock delivery at reduced energy levels, while polymorphic VT receives full energy shocks, balancing rapid response with energy conservation.
Data Source
AI summary
An implantable medical device system detects and treats monomorphic ventricular tachycardia (VT). The system includes a sensing module for receiving a cardiac signal and a therapy delivery module including a capacitor and an output circuit. A control module is coupled to the sensing module and the therapy delivery module and is configured to detect a tachycardia from the cardiac signal and initiate charging of the capacitor in response to detecting the tachycardia. The control module performs a method for simultaneously monitoring a voltage on the capacitor and a morphology of the cardiac signal during the charging and controls the therapy delivery circuit to deliver a shock pulse at less than a programmed shock energy in response to both the voltage reaching at least a minimum voltage and the morphology being monomorphic.