Which ECG finding is most consistent with a suspected tricyclic antidepressant overdose?

• A. Widened QRS
• B. Hypertension
• C. Elevated ST segment
• D. Shortened PR interval

Answer: (A)

TCA overdose blocks fast sodium channels in the heart, which slows how quickly electrical impulses move through the ventricles. That slowed conduction shows up on the ECG as a widening of the QRS complex. The broader the QRS, the more pronounced the sodium channel blockade and the greater the risk of serious problems like seizures or lethal arrhythmias, making QRS widening the most consistent and diagnostic finding in this context. Hypertension isn’t typical here and would suggest another cause; elevated ST segments aren’t a hallmark of TCA toxicity and aren’t expected from this mechanism; a shortened PR interval doesn’t reflect the conduction delay caused by sodium channel blockade. Recognizing a widened QRS helps guide urgent treatment, such as sodium bicarbonate therapy, to reverse the blockade and stabilize the patient.