Can an acetaminophen (Tylenol) overdose cause electrocardiogram (ECG) changes with prolonged QRS duration and nonspecific ST-T wave abnormalities?

ECG Changes in Acetaminophen Overdose

Acetaminophen overdose is not typically associated with ECG changes such as QRS prolongation and nonspecific ST-T wave abnormalities, and these findings should prompt investigation for other causes, particularly tricyclic antidepressant co-ingestion.

Understanding the ECG Changes

The ECG findings in this 17-year-old male with acetaminophen overdose showing QRS prolongation (116 ms initially, progressing to 122 ms) and nonspecific ST-T wave abnormalities are concerning and atypical for isolated acetaminophen toxicity.

Acetaminophen and Cardiac Effects

• Acetaminophen overdose primarily affects the liver and, to a lesser extent, the kidneys
• Direct cardiotoxicity from acetaminophen is rare and not well-established in the literature 1
• When cardiac abnormalities occur with acetaminophen overdose, they are typically secondary to hepatic failure complications rather than direct cardiac effects

Concerning ECG Findings

• QRS prolongation >100 ms is not a typical finding in acetaminophen toxicity
• Progressive widening of the QRS complex (from 116 ms to 122 ms over approximately 3.5 hours) suggests an ongoing process affecting cardiac conduction
• Nonspecific ST-T wave abnormalities further support the presence of a cardiotoxic agent

Differential Diagnosis of ECG Changes

Co-ingestion of Cardiotoxic Medications

• Tricyclic antidepressants: Most likely explanation for the observed ECG changes

  • TCAs are known to cause QRS prolongation and ST-T wave abnormalities 2, 3
  • Initial evaluation of QRS duration is an important predictor of serious arrhythmias in TCA overdose 2
  • QRS >100 ms is concerning for sodium channel blockade

• Other potential co-ingestions:

  • Sodium channel blockers (antiarrhythmics, local anesthetics)
  • Antipsychotics (particularly thioridazine, haloperidol)
  • Methadone or other opioids that can prolong QT interval 2

Metabolic Disturbances

• Electrolyte abnormalities, particularly:
  • Hyperkalemia (can cause QRS widening)
  • Hypokalemia (associated with acetaminophen overdose 4 and can cause ST-T wave changes)
  • Hypocalcemia or hypomagnesemia

Management Approach

Immediate Actions

1. Continuous cardiac monitoring is essential for all patients with ECG abnormalities 2, 3
2. Obtain serial ECGs to monitor for progression of conduction abnormalities 3
3. Comprehensive toxicology screen to identify potential co-ingestants, particularly TCAs
4. Check electrolytes and correct abnormalities promptly

Specific Management for Suspected TCA Toxicity

• Administer sodium bicarbonate for QRS >100 ms to reverse sodium channel blockade 2

  • Goal is to achieve serum pH of 7.45-7.55
  • This can shorten QRS duration and prevent progression to ventricular arrhythmias

• Avoid certain medications:

  • Beta-blockers (may worsen conduction abnormalities)
  • Class IA, IC, and III antiarrhythmics (may further prolong QRS/QT)

Continued Monitoring

• Do not transport patients with significant ECG abnormalities away from monitored settings 3
• Continue ECG monitoring until drug levels have decreased and ECG abnormalities resolve 3

Key Considerations

• The progressive QRS widening (116 ms to 122 ms) over a short time period is particularly concerning and requires immediate attention
• While acetaminophen can rarely cause myocardial injury 5, ECG changes of this nature are much more consistent with co-ingestion of cardiotoxic agents
• Patients with intentional acetaminophen overdose frequently ingest multiple substances
• Adolescents with self-harm attempts may not disclose all ingested substances

Conclusion

The ECG changes observed in this 17-year-old male with acetaminophen overdose are not typical of isolated acetaminophen toxicity and strongly suggest co-ingestion of a sodium channel blocking agent, most likely a tricyclic antidepressant. Management should focus on cardiac monitoring, identification of co-ingestants, and treatment of sodium channel blockade with sodium bicarbonate if TCA toxicity is suspected.