Wednesday, 2 October 2013

ECG of the Week - 30th September 2013 - Interpretation

This ECG is from a 88 year old male who presents following multiple episodes of pre-syncope during the day. Past history of hyperlipidaemia, hypertension, atrial fibrillation, and CVA.
Medications include warfarin, metoprolol, and a diuretic. He is not taking digoxin or other antiarrhythmics.
Check out the extensive and excellent comments on these ECG's from our original case post here. 
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I hope you enjoy the blog.





ECG 1 - on presentation
Click to enlarge

ECG 1 

Rate:
  • 126 bpm
Rhythm:
  • Regular
  • P waves
    • Negative leads I, aVL
    • Isoelectric lead II
    • Positive lead III
Axis:
  • Right axis deviation (+95 deg)
Intervals:
  • QRS - Prolonged (110ms)
  • QT - 280ms (QTc Bazette ~ 405 ms)
Segments:
  • ST Elevation leads aVR & V1 (0.5mm)
  • ST Depression leads II, III, aVF, V2-6
Additional:
  • rSR' Pattern V1
Interpretation:
  • AVRT (likely rhythm)
    • P wave morphology consistent with concealed left lateral accessory pathway
    • Other DDx Atrial tachycardia (less likely rhythm)
  • This is not AVNRT or Junctional Tachycardia
    • The p wave morphology is not consistent with these rhythms
    • For AVNRT & Junctional Tachy we should see negative P waves in leads II, III, aVF and positive P waves in aVL & usually lead I.
Differential diagnosis

Broad range of differentials for this ECG including:
  • Ischaemia
  • Electrolyte abnormality
  • Drug toxicity
  • Myocarditis
  • Pulmonary hypertension
  • ASD
Shortly after the ECG above patient had a brief period of asystole and the ECG following this episode is below.


ECG 2 - following asystole
Click to enlarge

ECG 2 


Rate:
  • 42
Rhythm:
  • Regular
  • Sinus rhythm
Axis:
  • Right axis deviation (+95 deg)
Intervals:
  • PR - Prolonged (240ms)
  • QRS - Normal (100ms)
  • QT - 440ms (QTc Bazette 365 ms)
Segments:
  • ST Elevation aVR (0.5mm)
  • ST Depression leads II, III, aVF, V2-6
Additional:
  • Biphasic P wave V1
  • rSR' pattern V1

So what happened ?

We have an elderly  with a history of atrial fibrillation presenting with a tachyarrhythmia followed by an asystolic event and subsequent bradyarrhythmia. 

My initial thoughts for this case was one of sinus node dysfunction (tachy/brady syndrome).
The patient had a potasssium of 6.0 mmol/L and an initial troponin of 0.06 mcg/L [normal <0.05 mcg/L] which increased to 0.41 on serial testing, so a likely ischaemic precipitant for this event.
Whilst in the Emergency Department the patient had a second asystolic event which responded to atropine and precordial thump. Following pacing was performed and PPM insertion was planned. Unfortunately the patient's condition rapidly deteriorated with multi-organ failure, active treatment was ceased and palliative care measures instituted .

A number of comments suggested a possible PE in this case, however the patient is elderly and on warfarin which makes PE unlikely and the multiple syncopal episodes also don't favour PE given the absence of haemodynamic collapse. Given the subsequent arrest, if caused by PE, I would not expect to get ROSC without very aggressive therapy +/- lysis, whereas in this case the patient recieved a precordial thump with resultant rhythm above (ECG 2). The post ROSC ECG also shows a bradycardia, in the setting of PE we would expect to see a persistant tachycardia.

References / Further Reading

Life in the Fast Lane

  • AVRT here
  • Accelerated Junctional Rhythm here
  • Sinus Node Dysfunction here
Textbook
  • Chan TC, Brady WJ, Harrigan RA, Ornato JP, Rosen P. ECG in Emergency Medicine and Acute Care. Elsevier Mosby 2005.