Wednesday, 7 November 2012

ECG of the Week - 5th November 2012 - Interpretation


Another two parter for this fortnight.
 
This ECG is from an 83 year old male.
Presented with chest pain, nausea, dysponea following brief episode of LOC.
Past Hx - warfarinised, previous AF / flutter / bradycardia, PPM inserted 7 years prior.
 






 
Click to enlarge
 

Rate:
  • ~175
Rhythm:
  • Regular
  • No p waves visible

Axis:
  • Extreme Axis Deviation
Intervals:
  • PR - No P waves visible
  • QRS - Prolonged (160-200ms)
 
Additional:
  • Pacing Spikes Visible Intermittently
  • Pacing Spikes Interval 1000ms (60 bpm)
  • No evidence of pacing capture or fusion
  • Spikes best seen Leads II, aVR, V5/6
  • No concordance

Interpretation:

  • Broad Complex Tachycardia
  • Consistent with Ventricular Tachycardia
    • Patient Age
    • Extreme Axis Deviation
    • Broad - broad QRS
    • Not typical BBB morphology

  • Pacing Spikes - Pacer set to VVIR according to old notes
  • ? Failure to sense and capture

A bit more information for those of you who want to know.
This patient had a pacemaker inserted 7 years prior to this presentation.
Pacemaker settings:
  • Single lead placed in right ventricle
  • Pacing mode set to VVIR
  • Rate setting 60 - 110 bpm
I am planning to discuss this case with our cardiologist / electrophysiologist regarding the pacer + VT combination and will update this post after speaking with them.

For what happened next watch out of next weeks ECG !

Up-Date

We've been very fortunate to have two new authors join our blog team, Dr Sakeeb Razak and Dr Arieh Keren, both Cardiology Specialists.

Their thought's on this week's ECG are below.

Interpretation
  • Ventricular Tachycardia arising from the mid to distal third inferolateral / apical left ventricle.


Why it isn't Pacemaker Mediated Tachycardia (PMT)
 
  • It can not be a paced rhythm or PMT because of the RBBB morphology unless there is a lead in the left ventricle.
  • You need a dual chamber device programmed to at least DDD.
  • Results from retrograde conduction of a V paced event sensed as an A and thus tracked over and over.
  • The rate of PMT is at or below the upper tracking rate which is not the case here.
The presence of 'Pacing Spikes'
 
  1. Artefactual - Mostly likely by consensus
  2. The device is at End of Life and is defaulted to VOO mode at 60 bpm - Possibility
  3. The device battery is low and there is a magnet over it thus making it VOO.  The magnet rate is usually 85 or 100 bpm unless the battery is low - Possibility
  4. The device is at ERI (elective replacement, low battery and thus switched to VVI) and is pacing VVI with loss of sensing - Unlikely

References / Further Reading

Life in the Fast Lane

  • Ventricular Tachycardia here
  • Pacemaker Normal Function here
  • Pacemaker Malfunction here 
 
Textbook
  • Chan TC, Brady WJ, Harrigan RA, Ornato JP, Rosen P. ECG in Emergency Medicine and Acute Care. Elsevier Mosby 2005.