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:

• Smith SW. T/QRS ratio best distinguishes ventricular aneurysm from anterior myocardial infarction.Am J Emerg Med. 2005 May;23(3):279-87.
• Engel J, Brady WJ, Mattu A, Perron AD. Electrocardiographic ST segment elevation: left ventricular aneurysm.Am J Emerg Med. 2002 May;20(3):238-42.

On the web:

• Dr Smith's ECG Blog - Left ventricular Aneurysm Morphology Distorted by Right Bundle Branch Block, Mimicking Acute STEMI with RBBB
• Dr Smith's ECG Blog - Persistent ST elevation after previous MI, otherwise known as "LV aneurysm" morphology
• Dr Smith's ECG Blog - This ECG is nearly pathognomonic. What is it?
• Dr Smith's ECG Blog - Prolonged Chest Pain. Is this LV aneurysm or acute anterior STEMI? Acuteness of STEMI and viable myocardium.

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.