Which antipsychotic agent is contraindicated in patients with a history of myocarditis or cardiomyopathy due to its direct cardiotoxic effects?

Explanation

## Clozapine and Cardiotoxicity **Key Point:** Clozapine carries a black-box warning for myocarditis and cardiomyopathy, particularly in the first 4–8 weeks of therapy. It is absolutely contraindicated in patients with pre-existing myocarditis, cardiomyopathy, or significant cardiac disease. ### Mechanism of Clozapine-Induced Cardiotoxicity 1. **Direct myocardial inflammation:** Clozapine induces a hypersensitivity myocarditis, likely immune-mediated, characterized by eosinophilic infiltration and myocyte necrosis. 2. **Catecholamine surge:** Clozapine may trigger sympathomimetic effects leading to increased myocardial oxygen demand. 3. **Oxidative stress:** Generation of reactive oxygen species and metabolite-induced injury. 4. **Timing:** Risk is highest in the first month but can occur at any time during therapy. ### Clinical Presentation of Clozapine-Associated Myocarditis - Chest pain or dyspnea - Palpitations, tachycardia - Elevated troponin and CK-MB - ECG changes (ST elevation, T-wave inversion) - Echocardiographic evidence of wall-motion abnormality or reduced ejection fraction - Fulminant heart failure (rare but fatal) **High-Yield:** Clozapine is the only antipsychotic with a black-box warning for myocarditis and cardiomyopathy. Baseline cardiac assessment (ECG, troponin, echocardiography if indicated) is mandatory before initiation. Weekly troponin monitoring for the first 4 weeks is recommended in high-risk patients. ### Comparison with Other Atypical Antipsychotics | Agent | Myocarditis Risk | QTc Prolongation | Cardiomyopathy Risk | |-------|------------------|------------------|--------------------| | **Clozapine** | **High (black-box)** | Minimal | **High (black-box)** | | Risperidone | Low | Moderate | Low | | Olanzapine | Low | Minimal | Low | | Haloperidol | Low | High | Low | | Quetiapine | Low | Minimal | Low | **Clinical Pearl:** If clozapine is deemed essential in a patient with prior myocarditis, rechallenge is contraindicated. Alternative atypical agents (risperidone, olanzapine, quetiapine, aripiprazole) should be used. **Warning:** Do not confuse QTc prolongation (a risk factor for torsades de pointes, seen with haloperidol and risperidone) with direct myocarditis (unique to clozapine). Both are cardiac risks but have different mechanisms and management implications.