TCA Pre-ECG Requirement — MRCPsych Paper B MCQ

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ModerateMood DisordersTCA Pre-ECG RequirementMRCPsych Paper B

A 45-year-old man with depression and stable coronary heart disease has not responded to two adequate SSRI trials. After specialist review of alternatives and overdose risk, amitriptyline is judged to be the only feasible antidepressant option. A baseline ECG is arranged. Which pair of ECG features is the key pre-treatment safety focus?

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Correct answer: B — QTc interval and cardiac rhythm

Explanation lettering: C = shown as A · E = shown as C · A = shown as D · D = shown as E

B is correct. When a TCA is the only feasible option in someone vulnerable to cardiac arrhythmias, UK Specialist Pharmacy Service advice supports baseline ECG monitoring. TCAs can alter cardiac rhythm and prolong conduction intervals, including the QT interval. The amitriptyline SmPC specifically reports QT prolongation and arrhythmias and contraindicates treatment in patients with cardiac rhythm disorders. The QTc interval and rhythm are therefore the principal TCA-specific safety features to review. The other options describe components of general ECG interpretation, but P-wave morphology, ST/Q-wave findings, T-wave axis/R-wave progression and U-wave amplitude/QRS axis do not directly capture the characteristic proarrhythmic concern tested here.

Reference: NHS Specialist Pharmacy Service. Choosing an antidepressant for people with coronary heart disease, section 'Tricyclic antidepressants (TCAs)', updated 29 April 2025. https://sps.nhs.uk/articles/choosing-an-antidepressant-for-people-with-coronary-heart-disease/