APPENDIX C

Patient Management Recommendations for Sprint Fidelis® Leads
October 2007

This attachment accompanies Medtronic’s physician letter dated October 15, 2007 and provides greater detail on our recommendations for the ongoing management of patients with Sprint Fidelis leads.

Follow-Up of Chronically Implanted Leads

Based on our review of the available data, there does not appear to be a significant benefit to more frequent follow-up.

The effectiveness of routine monitoring or lead impedance alerts for identifying a lead integrity problem before an inappropriate shock occurs may be enhanced when VF initial Number of Intervals to Detect (NID) are set to nominal values of 18/24 or longer (since longer NIDs reduce the risk of inappropriate detection of short bursts of oversensing). Redetect NID should be set to 12/16. The use of Medtronic CareLink® to facilitate remote access to the device information is suggested.

In the event of a suspected lead fracture, a complete clinical evaluation should be performed. In addition, we recommend the following:

  1. Review of device diagnostic data including VT/VF episode log and stored episodes to look for evidence of aborted, non-sustained events. Review the EGMs from treated events for evidence of lead noise oversensing.
  2. When at least two (2) of the following three (3) criteria indicate abnormal values, the likelihood of a lead integrity issue is higher.¹
    • Lead Status Report: Sensing Integrity Counter (measure of general oversensing near ICD blanking)
      Abnormal values: > 300 counts (this will generate an observation on the Quick Look™ screen on GEM® III or later models) OR > 30 counts and average > 10 counts/day since first count
    • Non-Sustained Episode Report
      Abnormal values: > 2 Non-Sustained Tachyarrhythmia (NST) with average RR interval < 200 ms
    • Lead Impedance Report
      • Inspect the lead impedance trend report to determine the patient’s typical chronic impedance value.
      • Compare average daily/weekly impedance to the patient’s typical chronic impedance value. If one or more impedance values are greater than 2x the baseline, then the lead impedance should be considered abnormal.

test

Battery and Lead Measurement Report

Viewing the Sensing Integrity Counter Data

On the Model 2090 Programmer:

  • Interrogate the device
  • Select Data -Device/Lead Diagnostics
  • Select Battery and Lead Measurements
  • Select [Open Data]
  • Select Print to print the screen information

Note: If the Sensing Integrity Counter > 300, the programmer displays a Quick Look observation.

Setup of Performance Parameters to Follow Chronically Implanted Leads

Properly setting the thresholds for Lead Impedance alerts is critical to triggering the Patient Alert™. If the Patient Alert feature is enabled and the impedance is out of range, a device tone alert will sound. For Concerto®/Virtuoso® patients enrolled on the Medtronic CareLink® Network, a Medtronic CareAlert® notification will also be transmitted if Medtronic CareAlert notification for lead impedance is programmed ON. During the early stages of a conductor fracture, the impedance may significantly increase (e.g., two-fold increase) compared to the typical chronic impedance for a patient.

Medtronic recommends enabling the following Lead Impedance Out of Range Patient Alerts and Medtronic CareAlert notifications and establishing the associated maximum impedance threshold value as shown in the following table:

Lead Impedance Alert Recommended Maximum Impedance Threshold Value

RV Pacing

  • 1,000 ohms, if the typical chronic impedance for the patient is ≤ 700 ohms
  • 1,500 ohms, if the typical chronic impedance for the patient is > 700 ohms

RV Defibrillation

  • 100 ohms

SVC Defibrillation

  • 100 ohms

Reducing the Risk of Inappropriate Shocks Due to Lead Noise Oversensing

To reduce the risk of inappropriate shocks due to lead noise oversensing, Medtronic recommends programming parameters for VF detection duration to the nominal values as follows:

  • VF initial NID (number of intervals to detect) = 18/24 or longer
  • Redetect NID = 12/16

Clinicians should consider programming VF initial NID to 24/32 in Marquis® and later devices (i.e., Marquis, Maximo®, Intrinsic®, InSync MarquisTM family, EnTrust®, Virtuoso®, Concerto®) to further reduce the risk of inappropriate shocks due to lead noise oversensing. Programming VF initial NID to 24/32 in Marquis and later devices is estimated to have minimal impact on the total time to VF shock (compared to GEM III and earlier devices with NID = 18/24), thus minimizing the risk of delayed therapy or syncope.

Estimated Values GEM III and Earlier Initial NID = 18/24 Marquis and Later Initial NID = 18/24 Marquis and Later Initial NID = 24/32

Detection Time

5.4 seconds

5.4 seconds

7.2 seconds

Charge Time

7-14 seconds

7-9 seconds

7-9 seconds

Total Time to VF shock

12.4-19.4 seconds

12.4-14.4 seconds

14.2-16.2 seconds

Lead Noise Shock Reduction (compared to initial NID = 12/16)

Estimate a 15-29% reduction in inappropriate shocks

Estimate a 15-29% reduction in inappropriate shocks

Estimate a 27-67% reduction in inappropriate shocks

A retrospective review of Fidelis lead fracture data indicated:

  • That reducing the HV impedance alert from 200 ohms to 100 ohms would have provided an additional week’s notice for 26% of high voltage conductor fractures. There are no data to suggest that increasing the follow-up frequency for patients will provide additional benefit.
  • With RV Pacing Impedance Alert set to 1,000 ohms, 47% of patients would have four or more days notice, an additional 2% would have two days notice, and an additional 2% would have one day notice.
  • Manual review of other lead fracture prediction criteria (short interval counts, non-sustained VT, impedance trends, etc.), would identify an estimated 36% of patients if performed monthly, or 49% if performed weekly.

Reference

1

Gunderson BD, Patel AS, Bounds CA, et al. An algorithm to predict implantable cardioverter-defibrillator lead failure. J Am Coll Cardiol. November 2, 2004;44(9):1898-1902.

 


If you have questions or concerns, please contact your Medtronic Representative or Medtronic Technical Services at 1-800-723-4636 (US).