A patient ingested some unknown substance and presented with myoclonic jerks, seizures, tachycardia and hypotension. The ECG showed a heart rate of 120/minute with QRS interval of 0.16 seconds. The arterial blood gas revealed a pH of 7.25, PCO2 of 30 mmHg and HCO3 of 15 mmol/L. The most likely cause of poisoning is ingestion of:

Question

Image below highlights jugular foramen. Which of the following structures do not pass through the marked structure “A”?

Answer 1

The key clue in this vignette is the QRS interval of 0.16 seconds, a markedly widened QRS, together with seizures, tachycardia, hypotension and a high anion gap metabolic acidosis. Let's test each poison against this pattern.

Amanita phalloides: This mushroom poison causes severe vomiting and diarrhea first, then delayed liver failure over days. It does not cause an acute wide QRS or seizures soon after ingestion, so it does not match.
Ethylene glycol: This does cause a high anion gap metabolic acidosis, but through glycolic and oxalic acid buildup, along with intoxication and calcium oxalate crystals in the urine. It is not known for widening the QRS complex, so the ECG finding here does not point to it.
Imipramine: As a tricyclic antidepressant, imipramine blocks cardiac sodium channels, which widens the QRS in direct proportion to the dose taken. It also blocks acetylcholine, alpha, and histamine receptors, producing seizures, myoclonus, fast heart rate and low blood pressure together, exactly what this patient has. The metabolic acidosis follows from the seizures and poor tissue perfusion.
Phencyclidine: This causes agitation, nystagmus, and usually a rise rather than a fall in blood pressure, and it is not linked with QRS widening, so it does not fit the ECG picture.

The wide QRS interval is the strongest clue here, and among the four options only a tricyclic antidepressant like imipramine explains it along with the seizures and hypotension.

Let's summarize:

A widened QRS after an overdose points to sodium channel blockade, a hallmark of tricyclic antidepressant toxicity.
Ethylene glycol causes acidosis without QRS widening; Amanita and phencyclidine do not fit this timeline or ECG pattern.

So the poison responsible is imipramine, option (3).

Answer 2

The key clue in this vignette is the QRS interval of 0.16 seconds, a markedly widened QRS, together with seizures, tachycardia, hypotension and a high anion gap metabolic acidosis. Let's test each poison against this pattern.

Amanita phalloides: This mushroom poison causes severe vomiting and diarrhea first, then delayed liver failure over days. It does not cause an acute wide QRS or seizures soon after ingestion, so it does not match.
Ethylene glycol: This does cause a high anion gap metabolic acidosis, but through glycolic and oxalic acid buildup, along with intoxication and calcium oxalate crystals in the urine. It is not known for widening the QRS complex, so the ECG finding here does not point to it.
Imipramine: As a tricyclic antidepressant, imipramine blocks cardiac sodium channels, which widens the QRS in direct proportion to the dose taken. It also blocks acetylcholine, alpha, and histamine receptors, producing seizures, myoclonus, fast heart rate and low blood pressure together, exactly what this patient has. The metabolic acidosis follows from the seizures and poor tissue perfusion.
Phencyclidine: This causes agitation, nystagmus, and usually a rise rather than a fall in blood pressure, and it is not linked with QRS widening, so it does not fit the ECG picture.

The wide QRS interval is the strongest clue here, and among the four options only a tricyclic antidepressant like imipramine explains it along with the seizures and hypotension.

Let's summarize:

A widened QRS after an overdose points to sodium channel blockade, a hallmark of tricyclic antidepressant toxicity.
Ethylene glycol causes acidosis without QRS widening; Amanita and phencyclidine do not fit this timeline or ECG pattern.

So the poison responsible is imipramine, option (3).

Show Hint

The Correct Option is C

Solution and Explanation

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