Implantable Cardiac Sensing During MRI Noise Intervals
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Solution Overview
Problem
Magnetic resonance imaging (MRI) strong magnetic fields interfere with the operation of implantable medical devices (IMDs), causing parasitic currents that can lead to life-threatening fibrillation, inhibit necessary therapy delivery, and mask true arrhythmias, necessitating IMDs to be disabled during scans.
Innovation Solution
An implantable medical device (IMD) with sensing circuitry that detects and corrects for MRI-induced noise by applying blanking intervals, modifying signal segments, and analyzing biological signals to differentiate between physiologic and non-physiologic conditions, allowing continuous operation during MRI procedures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the IMD operates during MRI scans, then continuous patient monitoring and therapy delivery is maintained, but MRI-induced noise causes false arrhythmia detection and unnecessary therapy delivery
Solution Approach 1:
The system receives MRI scan timing information in advance from the MRI system, allowing it to proactively identify and flag arrhythmia detections that occur during MRI scans as potential false positives. This preliminary action enables the system to prevent unnecessary therapy delivery by recognizing the temporal correlation between MRI noise bursts and detected arrhythmias.
Solution Approach 2:
The system establishes bidirectional communication with the MRI system, where the IMD provides arrhythmia detection data to the MRI system, and the MRI system provides scan timing information back to the IMD. This feedback loop allows both systems to coordinate and distinguish between true arrhythmias and MRI-induced noise artifacts.
2Object-affected harmful factors
If the IMD is disabled during MRI scans to avoid harmful interference, then patient safety from false therapy delivery is ensured, but continuous monitoring and therapy delivery is interrupted
Solution Approach 1:
The IMD is pre-programmed with MRI scan timing information received from the MRI system before the scan begins. This allows the device to maintain operation during the scan while proactively recognizing and filtering out false arrhythmia detections that occur during known MRI noise periods, thus maintaining both safety and monitoring continuity.
Solution Approach 2:
The system dynamically adjusts its arrhythmia detection parameters based on the MRI scan timing. During MRI scan intervals, the system modifies its detection thresholds and algorithms to account for expected noise patterns, allowing it to maintain sensitivity to true arrhythmias while becoming tolerant of MRI-induced artifacts.
3Measurement precision
If the IMD filters out MRI-induced noise, then true arrhythmia detection accuracy is improved, but signal processing complexity and device computational load increases
Solution Approach 1:
Instead of implementing complex real-time noise filtering algorithms, the system receives MRI scan timing information in advance and uses this temporal information to simply flag and exclude detections during known noise periods. This approach achieves high detection accuracy through temporal correlation rather than complex signal processing.
Solution Approach 2:
The MRI scan timing information acts as an intermediary that bridges the gap between the IMD and the MRI system. Rather than directly filtering noise from the electrical signals, the system uses the timing information as a mediator to identify and exclude false detections, simplifying the signal processing requirements.
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
Enables reliable sensing and therapy delivery for IMDs during MRI scans by distinguishing MRI-induced noise from physiologic signals, preventing unnecessary pacing or shocks and ensuring arrhythmia detection.
Implementation Method 1
The leads, and/or the IMD itself, may also have a variety of sensors for sensing physiological signals within the heart of the patient, such as electrical sensors
Implementation Method 2
When patients with pacers or ICDs are exposed to MRI fields, RF fields of the MRI can induce currents along the conduction paths
Data Source
AI summary
An implantable medical device (IMD) is provided and includes sensing circuitry coupled to electrodes. The sensing circuitry is configured to sense electrical biological signals indicative of a non-physiologic condition of interest experienced by a patient during a magnetic resonance imaging (MRI) procedure, and in the presence of an MRI scanning sequence, the MRI scanning sequence includes at least one of radio frequency (RF) or gradient fields that are in an active state for active field intervals. The device includes memory to store the biological signals and to store program instructions and includes a processor that, when executing the program instructions, is configured to: determine start times for the active field intervals when the at least one of RF or gradient fields switch to the active state and manage generation of MRI-induced-noise corrected (MRI-INC) biological signals, based on the start times for the active field intervals, by at least one of: 1) applying a blanking interval to the sensing circuitry to blank a sensing operation during at least portions of the active field interval or 2) modifying segments of the biological signal sensed during at least the portions of the active field interval, and 3) comparing biologic signal sensed during at least the portions of the active field interval to a template. The device analyzes the biological signals for an indication that the patient is experiencing the non-physiologic condition.