Wednesday, 10 July 2013

ECG of the Week - 8th July 2013 - Interpretation

This ECG is from a 47 year old female.
She presents with acute onset severe dysponea.
Vitals signs are BP 95/42 RR 30 Sats 88% (Room Air)
Her ECG is below.




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Rate:
  • 102
Rhythm:
  • Regular
  • Sinus Rhythm
Axis:
  • Normal (~80 deg)
Intervals:
  • PR - Normal (~160ms)
  • QRS - Prolonged (100-120ms)
  • QT - 320ms (QTc Bazette ~410 ms)
Segments:
  • ST Elevation leads aVR (1.5mm) V1 (1mm) V2 (subtle)
  • ST Depression Leads I, II, III, V4, V5, V6
Additional:
  • T wave inversion leads III, aVR, V1, V2, V3
  • S wave lead I
  • Small Q waves (<1mm) leads II, III, aVF
  • RSR' pattern V1, V2
    • Partial / Complete RBBB - QRS varies 100-120ms
Interpretation:
  • The ECG findings really suggest two likely pathologies:
    • Pulmonary Embolism
    • ACS
  • With this clinical stem of hypoxia, hypotension, and pre-syncope I'd argue PE is more likely than ACS 
  • I would encourage anyone who hasn't had a look at the comments on this ECG from our readers to check them out here, at the bottom of the page.
Does the ECG help us in PE ?

The ECG in Pulmonary Embolism ultimately lacks sensitivity and specificity. Its most important role is the detection of another cause for the patients symptoms e.g. ACS or STEMI.
Some ECG features that are associated with PE are:
  • Normal ECG in 9-26% of cases
  • Sinus Tachycardia in 44-73% of cases
  • RBBB (Complete or incomplete) in 18-25% of cases
  • RAD in 16-23% of cases
  • P Pulmonale in 9-33% of cases
  • Supraventricular arrhythmia in 8-33% of cases
  • Clockwise rotation in 18-30% of cases
  • T inversion Right Precordial leads in 10-46% of cases
  • S1Q3T3 in 12-25% of cases
    • S1Q3T3 whilst oft quoted as 'the' ECG finding in PE lacks sensitivity, specificity, and is certainly not pathognomonic of PE.
The incidence of the ECG changes in PE vary greatly with textbook and the above list is an amalgamation of the figures from both Chan's ECG in Emergency Medicine and Chou's Electrocardiography in Clinical Practice.

ACS vs PE

Dr Smith has already done the work for me on this one, with a great case example, and a reference to an article by Kosuge et al. Head over to Dr Smith's blog post here and/or read the Kosuge et al. paper here.
The presence of T wave inversion in lead V1 plus lead III, as in our case here, was only seen in 1% of ACS patients versus 88% of patients with Acute Pulmonary Embolism (n=87 in ACS group, n=40 in PE group).
For a great review of the ACS vs PE issues check out @ETtube's blog the Chart Review post on 'A Clear cut case of ACS'

What happened ?

I was asked by @ETtube on twitter for the CXR of this case so here it is, check out her post on the CXR in PE for a great overview on the CXR features of PE:

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The patient had a CTPA, select images are below:

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Formal CTPA report: Saddle pulmonary embolism is noted. Heavy bilateral thrombus burden. There is CT evidence for right heart strain.

If you want to read more about CTPA and its role/limitations in PE severity assessment check out this article by Ghaye et al. here.

Our patient was then transferred to a Tertiary Centre and underwent a successful pulmonary embolectomy and was discharged from hospital within a week.


VAQ Corner

A 47 year old female presents to your regional ED.

She presents with acute onset severe dysponea.
Vitals signs are BP 95/42 RR 30 Sats 88% (Room Air)
Her ECG is above.

a. Describe and interpret her ECG (50%)

b. Outline your further management (50%)

I never really planned to 'answer' these VAQ questions in a formal manner on the blog. I just thought it may be of use to those of you, like myself, approaching our ACEM Fellowship exams as food for thought.
Regarding the management of PE I'd point people in the direction of the excellent EMCrit blog for some further reading, thoughts, and insight on the management of massive and sub-massive PE, some of which can be found here:

References / Further Reading

Life in the Fast Lane

  • ECG in Pulmonary Embolism here
Textbook
  • Chan TC, Brady WJ, Harrigan RA, Ornato JP, Rosen P. ECG in Emergency Medicine and Acute Care. Elsevier Mosby 2005.
  • Surawicz B, Knilans TK. Chou’s Electrocardiography in Clinical Practice. 6th Edition. Saunders Elsevier 2008.