ECG of the Week 15th September – Interpretation

This ECG is from a 65 year old man who has presented with central chest pain after a history of palpitations since yesterday.

He has a background of HTN and has had previous ablations.

  1. Interpret this ECG
  2. Describe your management.
  3. What Type of this dysrhythmia is shown?


  • Rate: 114
  • Rhythm: Narrow complex irregular tachycardia
  • Axis: normal (0-90)
  • Morphology: positive flutter waves seen noticeably in V1-3 and can be transcribed to inferior leads, regular rate 300/min
  • Intervals: Variable ventricular activity due to variable block (2:1, 3:1, 4:1 block)
  • Summary: Atrial flutter with variable block, abnormal re-entry pathway given previous ablations


Typical Atria flutter (or Atrial Flutter Type 1) can be split into 2 groups according to the types of pathway involved. The first –  Type 1 Anticlockwise Reentry – shows negative flutter waves in inferior leads and positive flutter waves V1. This is the commonest form and seen in 80-90 % of cases of Flutter.

In a clockwise pathway (Type 1 Clockwise Reentry) you see the opposite pattern with inverted flutter waves in V1 and positive flutter waves in inferior leads.

This ECG, however, shows positive flutter leads in both inferior and chest leads which means that this is Type II or Uncommon / Atypical Flutter (whereby flutter waves do not fit the criteria discussed above) This Uncommon flutter has been less extensively studied but can be seen in patients who are taking medications (especially antiarryhtmics), have severe chamber dilatation, or, like in this patient, have had previous ablation treatments.


Further Reading – Textbook:

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