Exercise Intolerance...

Trace category: 

Hello everyone,

Monitored AF episode from a Medtronic Consulta CRT-P in a 12 yo dependent patient.

What do you think happened? What do you propose?

Thank you

S Ploux

Mode DDD Lower 45 bpm Paced AV 130 ms
Mode Switch 207 bpm Upper Track 180 bpm Sensed AV 100 ms
Rate Response
ADL Rate 95 bpm
Optimization On
ADL Response 3
Exertion Response 3
Activity Threshold Medium Low
Activity Acceleration 30 sec
Activity Deceleration Exercise
ADL Setpoint 38
UR Setpoint 191

PVARP 200 ms
PVAB Interval 150 ms
PVAB Method Partial
AV Therapies
Rate Adaptive AV On
Start Rate 80 bpm
Stop Rate 175 bpm
Min PAV 80 ms
Min SAV 50 ms
AT/AF Detection  
Detection   A. Interval (Rate)  
  AT/AF 290 ms (207 bpm)


Interesting tracing with alot going on!

  • sinus tachycardia at ~210/min (young patient, active sensor, typical slowing at the end and the title suggests exertion) 
  • maximal tracking at 180 bpm causes Wenckebach phenomenon (first railroad track on tachygram)
  • AS-AS shortens to 280 ms and AT/AF is diagnosed (programmed at 290 ms)
  • switch to DDI mode
  • [1 minute of no EGM/markers]
  • fallback ventricular pacing at ~150 bpm.
  • since there is T-wave oversensing, there is intermittent ventricular pacing at 97 bpm (210+410ms, second railroad track on tachygram)
  • this drop in frequency during peak exercise explains the exercise intolerance
  • slowing down of sinus tachycardia
  • less sensed atrial events means the end of 'AF/AT' for the device
  • mode switch (marked 'MS') back to DDD
  • slowing down of sinus tachycardia to maximal tracking rate
  • speeding of ventricular pacing since 1-to-1 conduction is possible at maximal tracking rate 
  • end of the recording with probable further slowing of the sinus rate

I would suggest to change the AT/AF zone to lower than 290 ms so that her sinus tachycardia doesn't induce an inappropriate mode switch (with associated T-wave oversensing and slow pacing) in the future. I would not recommend increasing the maximal tracking rate because of the risk of 2-to-1 block. I would accept Wenckebach pacing at high sinus rates as in general, this is far less symptomatic than what we see here.

Hi Marc,

Not that I dislike your comments my friend but It would be nice to see new authors on this forum...

I agree with your clear analysis of the device behavior. I would highlight two points:

- TWOversensing is for me a marker of poor tolerance. Repolarization is modified consecutively to the A-V dissociation and the inappropriate drop in V rate. This is not the first time I see that.

- I would suggest to rise the AF limit indeed. But the UTRate too. Always better to have a 1:1 conduction at the top of exercise. (2:1 point is PVARP 200+ SAV 50ms /240bpm in the present case).

Thanks again Marc