A forgotten cause of wide complex tachycardia

Area of Science:

• Cardiology
• Clinical Toxicology
• Pharmacology

Background:

• Wide complex tachycardia is a known complication of acute tricyclic antidepressant (TCA) overdose.
• Standard management protocols exist for acute TCA toxicity.
• Chronic TCA use can lead to electrocardiographic abnormalities.

Observation:

• A patient presented with wide complex tachycardia.
• Acute TCA overdose was definitively ruled out.
• The patient's presentation included pre-existing chronic electrocardiographic abnormalities.

Findings:

• The wide complex tachycardia responded to standard treatments typically used for TCA toxicity.
• This response, in the absence of acute overdose, suggested an alternative etiology.
• The combination of chronic ECG changes and response to treatment pointed towards acute on chronic TCA toxicity.

Implications:

• This case broadens the differential diagnosis for wide complex tachycardia in patients with a history of TCA use.
• It underscores the importance of considering acute exacerbations of chronic TCA toxicity, not just acute overdose.
• Clinicians should consider standard TCA toxicity management even when acute overdose is excluded, particularly in patients with chronic ECG changes.