Wednesday, 14 August 2013

ECG of the Week - 12th August 2013 - Interpretation

I unfortunately have no clinical information on this ECG, but it looks interesting :-)
Check out our original post of this ECG and the excellent comments here.




Click to enlarge
Rate:
  • Ventricular rate 42 bpm
  • Atrial rate ~230 bpm
Rhythm:
  • Irregular ventricular activity
  • Regular atrial activity
    • Flutter waves
Axis:
  • Normal (~75 deg)
Intervals:
  • PR - Nil P waves visible
  • QRS - Prolonged (120ms)
  • QT - 400ms
Segments:
  • Minor ST depression V4-6
Additional:
  • rSR' Pattern V1-2
  • Variable notching of QRS complexes secondary to superimposed flutter waves
  • Flutter waves
    • Alternating positive / negative morphology in inferior leads
    • Flutter waves are narrow and small
    • Relatively long isoelectric segment
Interpretation:
  • Atrial flutter
  • Variable block

Dr Arieh Keren and Dr Shakeeb Razak, electrophysiology specialists and ECG of the Week blog team members, have reviewed this ECG and shared there thoughts below:

Atypical vs typical flutter

  • Typical atrial flutter involves the cavotricuspid isthmus (CTI) 
  • Atypical flutter involves a different location than the CTI.

Micro vs macro re-entrant circuit

  • Given the small flutter waves and isoelectric segment length this is more likely to be micro re-entry flutter.
  • Macro re-entry flutter results in the classic saw tooth pattern with atrial activation occuring throughout the flutter cycle length.

Underlying cause in this case

  • The alternating positive / negative atrial morphology suggests an uncommon circuit type.
  • A possibility is two seperate micro re-entry ciruit close to each other.
  • This suggests a more likely cause in this case of:
    • Previous cardiac surgery
    • Congential cardiac disease
    • Major metabolic derrangement
    .
Further Reading Recommendations

Dr Razak has suggested some interesting articles which further explore some of the features and questions raised by this ECG.


Both papers provide in-depth reviews of atrial flutter classifications, both new & old, and how the ECG and advanced EP techniques can help differentiate them

Causes of Atrial Flutter

There are a wide range of general potential causes for atrial flutter with variable block including:
  • Ischaemia
  • Sinus node dysfunction
  • Drugs
    • Digoxin
    • Beta-blockers
    • Calcium-channel blockers
    • Other anti-arrhythmic drugs
  • Electrolyte abnormality
  • Acid / base disturbance
  • Myocarditis
  • Cardiomyopathy
  • Endocrine
    • Hyper- / hypo-thyroid
  • Environmental
    • Hypothermia

VAQ Corner

A 83 year old patient presents to your Emergency Department complaining of lethargy, nausea, and vomiting. There are on multiple medications but are unable to remember their names.
BP 105/64 RR 17 Temp 37.4 C

Describe and interpret their ECG (100%)

References 

Life in the Fast Lane
  • Atrial flutter here
Textbook

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