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- QRS - Prolonged (140ms)
- Concordant ST depression in leads V3-6
- Limb leads show expected discordance
- 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
- Chan TC, Brady WJ, Harrigan RA, Ornato JP, Rosen P. ECG in Emergency Medicine and Acute Care. Elsevier Mosby 2005.