20 year old male presenting with seizures. BP 80/50.
Describe and interpret this ECG
ECG ANSWER and INTERPRETATION
- Broad complex tachycardia, rate ~ 130 bpm.
- The rhythm is likely sinus tachycardia with a 1st degree AV block — note the “camel hump” appearance to the T waves indicating a hidden P wave.
- Interventricular conduction delay (QRS duration > 100ms, not typical LBBB / RBBB morphology)
- Right axis deviation.
- Secondary R’ wave in aVR > 3 mm.
In the context of a patient presenting with seizures and hypotension, the combination of…
- QRS broadening > 100 ms
- R’ wave in aVR > 3 mm
… is highly suggestive of poisoning with a sodium-channel blocking agent — e.g. tricyclic antidepressant.
The sinus tachycardia may be due to the anticholinergic effects of the TCA.
In the context of sodium channel blockade:
- A QRS duration > 100 ms is predictive of seizures.
- A QRS duration > 160 ms is predictive of cardiotoxicity.
This patient is already manifesting life-threatening toxicity and needs aggressive resuscitation, including:
- Serum alkalinisation with NaHCO3 to reverse pH-dependent toxicity.
- Intubation and hyperventilation aiming for alkaline arterial pH (e.g. 7.45 to 7.55).
- Seizure management with benzodiazepines.
- BP management with fluid boluses +/- pressors.