A 52-year-old man with a history of myocardial infarction 6 months ago presents with major depressive disorder. His ECG shows normal QTc interval. Which antidepressant is the safest first-line choice?

Explanation

## Drug of Choice: Sertraline **Key Point:** SSRIs (especially sertraline) are the safest first-line antidepressants in post-MI patients because they lack cardiac conduction effects, have no anticholinergic activity, and carry no risk of arrhythmias — critical in a compromised myocardium. ### Cardiac Safety Profile Comparison | Aspect | Sertraline (SSRI) | Nortriptyline (TCA) | Doxepin (TCA) | Imipramine (TCA) | |--------|-------------------|-------------------|---------------|------------------| | **QT prolongation** | Minimal | Moderate–High | Moderate–High | High | | **AV conduction delay** | None | Yes | Yes | Yes | | **Anticholinergic effects** | None | Moderate | High | High | | **Orthostatic hypotension** | Minimal | Significant | Significant | Significant | | **Cardiac arrhythmia risk** | Very low | Moderate–High | Moderate–High | High | | **Safe in post-MI patients** | ✓✓ | ✗ | ✗ | ✗ | | **FDA-approved for depression post-MI** | ✓ | ✗ | ✗ | ✗ | **High-Yield:** SSRIs are preferred in patients with cardiac disease, prior MI, heart failure, or conduction abnormalities. TCAs are contraindicated or require extreme caution in these populations. ### Why TCAs Are Dangerous in Post-MI Patients 1. **Quinidine-like effects:** TCAs slow cardiac conduction (prolong PR, QRS, QT intervals) — risk of heart block or ventricular arrhythmias in a vulnerable myocardium. 2. **Anticholinergic activity:** Increases heart rate and myocardial oxygen demand — harmful post-MI. 3. **Orthostatic hypotension:** Reduces coronary perfusion pressure in a patient already at risk of reinfarction. 4. **Arrhythmogenic:** Direct myocardial depressant and pro-arrhythmic, especially at higher doses. **Clinical Pearl:** Sertraline has the additional advantage of a favorable drug interaction profile and is well-tolerated in elderly post-MI patients with comorbidities. **Warning:** Do NOT use TCAs (nortriptyline, doxepin, imipramine) as first-line in cardiac patients. If a TCA is absolutely necessary, nortriptyline is the "safest" TCA due to lower cardiotoxicity than imipramine or doxepin — but SSRIs remain preferred.