Wednesday, 5 March 2014

ECG of the Week - 3rd March 2014 - Interpretation

This ECG is from a 70 yr old patient with a history of ischaemic heart disease complicated by ischaemic cardiomyopathy (LV ejection fraction of 27%) in has an AICD in situ. 
The patient presented with worsening dysponea without chest pain. 
His intial serial ECGs are below.




ECG 1 - Click to enlarge

Rate:
  • ~90 bpm
Rhythm:
  • Regular
  • Sinus Rhythm
  • Last complex PVC
Axis:
  • LAD
Intervals:
  • PR - Prolonged (220ms)
  • QRS - Normal (100ms)
  • QT - 320ms (QTc Bazette 380-400 ms)
Segments:

  • ST elevation leads III, V1-5
  • ST depression (minor) lead I

Additional:

  • Q wave V1-2 
  • QS Wave V3-4
  • T inversion leads aVR, aVL
  • Voltage criteria LVH - aVR ~1.2mV
Interpretation:

ECG features stongly suggest an old anteroseptal MI, with Q / QS waves in precordial leads, a lack of significant ST depression, and a pain-free patient with a known previous ischaemic insult.

This patient was admitted and investigated for dysponea further with the following investigations:

Myocardial Perfusion Scan

  • Large anteroseptal and apical infarction
  • Small area of reversible ischaemia in the mid-to-basal anterior wall

Echo

  • Severely impaired systolic function
  • Large anteroapical aneurysm
  • No LV thrombus
  • LV ejection fraction 27%
For more on LV aneurysm check out the following papers:


ECG 2 - Click to enlarge



Rate:

  • Mean ventricular rate 60bpm
  • Regular atrial activity at ~62 bpm
Rhythm:
  • Regular pacing spikes @ 60 bpm
  • Complexes 1-5 V. paced
  • Complexes 6-10 progressive morphology change
    • Preceeded by p waves with pr segment progressive lengthening 160-220ms
Axis:
  • LAD
Intervals:
  • PR - Progressively prolongs in relation to QRS complex
  • QRS - Complexes 1-6 - Prolonged
  • QRS - Complexes 7-10 - Normal
Segments:
  • Discordant ST segment / T wave change
    • Complexes 1-5
Additional:
  • Pacing spike occurs withtin QRS for complexes 8-10
    • Morpholgy similar to native sinus beats
    • Pseudo-fusion beats
Interpretation:
  • Pacing mode likely VVI 60 bpm
  • Single chamber device - hence no atrial sensing
  • Isorhythmic sinus & pacing rate 
    • Both ~60 bpm
  • For complexes 8-10 these are sinus conducted and given the near identical pacing and sinus rates the QRS complex has begun to form at the same time the pacing spike is delivered - causing a pseudofusion beat. The QRS complex has not yet been detected by the AICD, remebering the AICD uses local electrogram sensing, so a spike is delivered during the initial portion of the QRS which in effect does nothing.

References / Further Reading

Life in the Fast Lane

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