RV Lead Noise Discrimination Feature
The RV Lead Noise Discrimination algorithm differentiates RV lead noise from VT/VF by comparing a far-field EGM signal to near-field sensing. If lead noise is identified, VT/VF detection is withheld, and an RV Lead Noise alert is triggered.
RV Lead Noise Discrimination has been demonstrated to significantly reduce inappropriate detection due to lead noise.1
This feature can be found in some Medtronic ICD and CRT-D devices. Please go to manuals.medtronic.com or consult with your local Medtronic representative regarding device models available in your geography.
RV Lead Noise Discrimination algorithm is nominally programmed On with a timeout of 45 seconds.* The Timeout allows for the device to withhold detection and therapy for a RV lead noise episode for the programmed amount of time before delivering therapy. This timeout can be extended or turned off by the clinician.
To program this feature, go to Params -> Detection (V.)...
Lead noise oversensing is typically isolated to the near-field EGM (RVtip-RVring sense channel). Therefore, the RV Lead Noise Discrimination Algorithm uses a far-field electrogram signal (Can to RV coil or RV coil to SVC) to confirm the fast sensed intervals that are detected on the near-field electrogram. In the presence of lead noise, the ventricular senses on the near-field do not represent an arrhythmia. If a true arrhythmia is occurring, then the ventricular senses on the near-field should also correlate to deflections on the far-field signals.
The RV Lead Noise Discrimination feature applies only to initial detection. The algorithm uses events sensed on the ventricular near-field channel to determine a window to analyze the peak-to-peak far-field channel amplitude.
The algorithm looks at a set of 12 ventricular sensed events (near-field) and determines that there is noise if both conditions listed below are met:
- The average of the two smallest far field signals is less than 1 mV and
- There is a significant difference between the smallest and largest far-field signals.
A noise counter increments based on a set of 12 events within a rolling window. Once detection is reached, if at least 3 out of the last 12 sets are classified as noise, detection is withheld. This allows the device to withhold detection if consistent noise is present on the sensing lead. When detection is withheld, the device will label the interval as Noise with an “N” below the interval that satisfied the Noise criterion on the EGM decision channel.
The rhythm is continually analyzed and validated for noise while the ventricular senses remain in the VF zone or until the timeout is reached. Once Timeout is reached, detection will resume and no longer be withheld due to noise discrimination.
RV Lead Noise has both an audible alert and a programmable wireless CareAlert™, which is transmitted to the CareLink™ Network if applicable. The audible alert continues to sound at regular intervals until the device is interrogated.
The Quick Look™ II screen will show the number of ventricular oversensing episodes (VOS) detected.
When RV Lead Noise is detected, the device stores a Ventricular Oversensing - Noise episode. The example below displays the interval plot and EGM of an episode of Ventricular Oversensing due to Noise. Notice the fast, irregular, and non-physiologic V-V intervals on the interval plot. The presence of noise is confirmed on the EGM. The intervals on the EGM are labeled “N” to represent the determination that they are due to noise and not a true arrhythmia. Note that the duration of the episode is 16 seconds with no therapies delivered.
The RV Lead Noise Discrimination algorithm can withhold 83.7% of inappropriate detection for lead sensing noise.1 Using the Protecta Performance Model, the RV Lead Noise Discrimination algorithm, combined with ATP Before/During Charging, TWave Discrimination, and SVT discriminators applied in the VF zone, significantly reduced shock frequency when tested on stored episodes from the SCD-HeFT Trial. This model that combined existing and new shock reduction features predicted 98% of patients would be free of inappropriate shocks 1 year after implant, and 92% at 5 years post-implant.2
- Zhang X, Volosin KJ, Kumar A, Gunderson B, Gilberg J, Withholding ICD Shocks for Detected Lead Fracture, HRS Conference, May 2009.
- Volosin K, Exner DV, Wathen MS et al., Virtual ICD: A Model to Evaluate Shock Reduction Strategies, HRS Conference, May 2010.
Sources: Medtronic Protecta™ XT DR Clinician Manual; Medtronic Protecta™ XT CRT-D Clinician Manual.