ECG of the Week: ECG of the Week - 25th January 2015

Wednesday 27 January 2016

ECG of the Week - 25th January 2015 - Interpretation

This week's ECG is another ECG from our patient from last week and the week prior to that. He is an 88yr old male who had an episode of VT on a background of ischaemic cardiomyopathy. Following successful cardioversion he underwent an ICD insertion. He then presented to the Emergency Department complaining of palpitations.

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Rate:

Rhythm:

Regular

Axis:

Intervals:

QRS - Prolonged (140ms)

Segments:

Concordant ST depression in leads V3-6
Limb leads show expected discordance

Additional:

Regular atrial activity best seen in leads V3-5 in 1:1 ratio with QRS without AV dissociation
No precordial concordance
RBBB Morphology Rsr' in lead V2
Absence of pacing spikes

Interpretation - Broad differentials include:

SVT with aberrancy / pre-existing conduction abnormality

Clearly different morphology from prior VT seen here
Lack of AV dissociation / Concordance

Prior episode of VT and known cardiomyopathy
Not favored due to lack of ICD shock delivery and morphology features noted above - possibility of ICD malfunction should be considered

Pacemaker mediated tachycardia

Nil evidence of pacing spikes
Morphology clearly different when compared with prior v-paced ECG here

What happened ?

The treating clinicians were concerned about the possibility of ICD malfunction and treated the ECG as VT and performed a successful DC cardioversion.

So why didn't the ICD shock the patient ? There are only two simple possibilities:

Something is wrong with ICD
It's not VT

In this case the ICD didn't fire because this wasn't VT. On pacemaker interrogation this was an episode of atrial tachycardia with aberrant conduction and a further episode whilst an in-patient was terminated with iv sotalol.

References / Further Reading

Life in the Fast Lane

Textbook