In suspected tricyclic antidepressant overdose, which diagnostic test is most informative?

• A. EKG showing a prolonged QT
• B. Brain MRI
• C. Complete blood count
• D. Lumbar puncture

Answer: (A)

In suspected TCA overdose, the most informative test is the ECG because the drugs cause dangerous cardiac conduction abnormalities by blocking fast sodium channels. This blockade widening the QRS complex (and can be reflected in QT changes) directly signals the degree of cardiotoxicity and helps predict risk of seizures or ventricular arrhythmias, guiding urgent treatment such as sodium bicarbonate therapy. While imaging or labs like brain MRI, CBC, or lumbar puncture won’t reveal the acute, drug-specific cardiac effects, the ECG provides the real-time picture of how the heart is being affected and whether aggressive cardioprotective measures are needed.