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

  • ~175
  • Regular
  • No p waves visible

  • Extreme Axis Deviation
  • PR - No P waves visible
  • QRS - Prolonged (160-200ms)
  • 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


  • 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 !


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.

  • 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 
  • Chan TC, Brady WJ, Harrigan RA, Ornato JP, Rosen P. ECG in Emergency Medicine and Acute Care. Elsevier Mosby 2005.