ECG of the Week – 22nd September 2014 – Interpretation

Sorry but I don't have any clinical information on this ECG at all but that hasn't stopped us before.

So what's going on here ?

Check out the great discussion on this ECG in the comments section from our original post.

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Numbered Ventricular Complexes
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Rate:
  • Mean ventricular rate 54 bpm
Rhythm:
  • Interesting !
  • P waves
    • Precede all ventricular complexes
    • P waves occur regularly every 760 ms
    • EXCEPT between complexes #2/3, 4/5, 7/8 where the P waves is dropped
    • The gap between the P waves either side of the pause is 1520 ms 
      • i.e. double the normal P-P interval
  • QRS Complexes
    • Progressive PR lengthening
    • Progressive R-R shortening
    • Grouped beatings
    • The dropped QRS is not preceded by a P wave
      • Not just 2nd Degree AV Wenckebach
Axis:
  • Normal
Intervals:
  • PR - Initially normal (180ms) then progressive lengthening
  • QRS - Normal (100ms)
  • QT - 440ms 
Segments:

  • ST Depression leads II, III, aVF, V2-6

Additional:

  • T wave inversion Leads III, aVR, V1-3
  • rSR' Pattern V1
  • Deep inferior Q waves with smaller lateral Q waves
  • Baseline irregularity
  • Lead I rhythm strip makes P waves more difficult to identify

Interpretation

So we have clear evidence of a AV Wenckebach but where do the P waves go ?

Frequent ECG of the Week commenter / ECG author / blogger / legend Ken Grauer shares his thoughts on our missing P waves:

I strongly suspect that there is a blocked PAC that causes the pause (and terminates the Wenckebach cycles) - but unfortunately in the long lead I it is very difficult to be certain of this ... I do think I see tiny-but-real differences in the T wave of the beats that initiate the pause (in lead II for beat #2; in aVF for beat #4; and in V2 for beat #7)

My other theory:

Presence of a 2nd Degree Type II SA exit block in addition to our 2nd Degree Type I AV block !
There is a regular P-P interval with the interval including the dropped P wave being twice that of the normal P-P interval. The causative factors for both types of block are virtually identical - ischaemia, drugs, electrolyte abnormality, cardiomyopathy, myocarditis etc.

Do I have a definitive answer ? No

I don't have any other ECG's or clinical information on this case. A longer rhythm strip, serial ECG's, old ECG's, more clinical information, and ideally lead II as the rhythm strip may shed more light on the likely rhythm disturbance and causative factors.

References / Further Reading

Life in the Fast Lane

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

ECG of the Week – 15th September 2014 – Interpretation

This week's ECG is an old one from my collection.
It's from a 75yr old female. I don't have any other clinical information on this case unfortunately.




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Rate:
  • ~145 bpm
Rhythm:
  • Subtle irregularity in rate
    • Periods of fixed rate of 150 bpm leads V1-3
    • Periods of rate change best seen in lead V6
  • Nil p waves seen
Axis:
  • LAD
Intervals:
  • QRS - Prolonged (120-140ms)
  • QT - 400ms (QTc Bazette 380-400 ms)
Segments:
  • Discordant ST segment / T wave changes

Additional:

  • LBBB morphology
    • Sgarbossa negative
  • Subtle change in QRS morphology best seen V4-6 as rate changes
Interpretation:

  • Wide Complex Tachycardia with LBBB morphology and left axis deviation

    So what are the differentials ?

    One of our electrophysiologists has looked at this ECG and had these comments.

    • SVT - with either baseline LBBB, would need old ECG's to compare, or aberrancy / rate related block.
      • Most likely mechanism is atrial tachycardia or atrial flutter with 2:1 block with slower variable block at start / end of rhythm strip.
    • VT - bundle branch re-entry
    • Antidromic AV re-entry tachycardia with atriofascicular pathway
    • Pacemaker mediated tachycardia - no obvious pacing spikes but these aren't always seen as in this case from Ed Burns 

    Dr Razak has also highlighted some excellent resources on this ECG diagnostic challenge:

    • Neiger JS, Trohman RG. Differential diagnosis of tachycardia with a typical left bundle branch block morphology. World J Cardiol. 2011 May 26;3(5):127-34. PMID: 21666813 Full text here.
    • Sousa PA, Pereira S, Candeias R, de Jesus I. The value of electrocardiography for differential diagnosis in wide QRS complex tachycardia. Rev Port Cardiol. 2014 Mar;33(3):165-73. PMID: 24656320 Full text here

    But remember it's all about the patient

    • What symptoms does the patient have ?
    • Do they have signs of clinical compromise ?
    • Do you need to do something now ?



    References / Further Reading

    Life in the Fast Lane

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

    ECG of the Week – 8th September 2014 – Interpretation

    This week's ECG is from a 75 yr old female. Past medical history of GORD. She presented complaining of 3 hours of epigastric pain with severe nausea and multiple episodes of vomiting.




    Click to enlarge

    Rate:
    • 66 bpm
    Rhythm:
    • Regular
    • Sinus rhythm
      • Baseline artifact makes P waves difficult to see but best seen in leads V1-3
    Axis:
    • Normal
    Intervals:
    • PR - Prolonged (280ms)
    • QRS - Normal (80-100ms)
    • QT - 380ms (QTc Bazette 400 ms)
    Segments:

    • ST Elevation leads III, aVF (<1mm)
    • Flat ST depression V1-3

    Additional:

    • T wave inversion leads I, aVL, aVR, V1-3
    • Prominent T waves leads III, aVF, V6
    • Prominent R wave lead V2

    Interpretation:


    • Infero-postero-lateral MI

    What happened ?

    The patient had posterior leads performed, ECG below:




    Posterior leads show clear ST elevation and the eagle-eye'd among you will notice that leads V1-3 are clearly different from the first ECG.

    Our local lead set-up means V1-3 on this ECG are certainly leads V4-6 but haven't been labelled as such. 

    The patient was transferred for urgent PCI and a lesion was stented. 

    Unfortunately the hospital discharge summary doesn't state where the culprit lesion was !!



    References / Further Reading

    Life in the Fast Lane

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