A 52-year-old woman with hypertrophic cardiomyopathy and a family history of sudden cardiac death presents with palpitations and syncope. Holter monitoring reveals frequent premature ventricular contractions and non-sustained ventricular tachycardia. She has normal renal and hepatic function. What is the first-line antiarrhythmic drug for this patient?

Explanation

## First-Line Antiarrhythmic in Hypertrophic Cardiomyopathy **Key Point:** Beta-blockers are the first-line pharmacological agents for suppression of ventricular arrhythmias in hypertrophic cardiomyopathy (HCM), providing both symptom relief and a reduction in arrhythmia burden. ### Rationale in HCM Beta-blockers (e.g., metoprolol, atenolol) are preferred in HCM because they: 1. Reduce left ventricular outflow tract (LVOT) obstruction by decreasing heart rate and contractility, prolonging diastolic filling time 2. Slow AV conduction and prolong refractoriness (negative dromotropic effect) 3. Reduce myocardial oxygen demand, addressing the ischemic substrate for arrhythmias 4. Suppress ectopic activity and re-entrant mechanisms underlying PVCs and NSVT 5. Are well-tolerated with normal renal and hepatic function (as in this patient) ### Why Other Agents Are Suboptimal or Contraindicated | Agent | Role in HCM | Rationale | |-------|-------------|-----------| | **Beta-blockers** | **First-line** | Reduce LVOT obstruction + suppress arrhythmias | | **Amiodarone** | Second-line | Reserved for refractory arrhythmias or patients ineligible for ICD; significant toxicity profile limits first-line use | | **Flecainide** | **Avoid** | Class IC agents are proarrhythmic in structural heart disease (post-CAST trial evidence); may worsen outcomes in HCM | | **Verapamil** | **Use with caution** | A non-dihydropyridine CCB used as an alternative in non-obstructive HCM when beta-blockers are not tolerated; however, it can precipitate hemodynamic collapse in severe obstructive HCM (especially with high resting gradients or elevated filling pressures) and is not preferred over beta-blockers as first-line antiarrhythmic therapy | | **Disopyramide** | Adjunct | Used alongside beta-blockers specifically for LVOT obstruction reduction, not as a standalone antiarrhythmic | **High-Yield:** In HCM with syncope and a family history of sudden cardiac death (SCD), the patient meets high-risk criteria. Beta-blockers address the arrhythmia pharmacologically, but **ICD implantation** is the definitive intervention for SCD prevention in high-risk HCM (≥1 major risk factor: family history of SCD, unexplained syncope, NSVT, maximal wall thickness ≥30 mm, or abnormal BP response to exercise). Beta-blockers serve as essential adjunctive therapy alongside ICD placement. **Clinical Pearl:** Verapamil is not universally contraindicated in HCM — it is an acceptable alternative in *non-obstructive* HCM when beta-blockers are not tolerated. However, in *obstructive* HCM (especially with high LVOT gradients), verapamil's vasodilatory effect can paradoxically worsen obstruction and cause hemodynamic collapse. Given the uncertainty in this stem, beta-blockers remain the safer, evidence-based first choice. **Mnemonic:** **HCM-BETA** = Hypertrophic Cardiomyopathy → Beta-blockers are first-line Antiarrhythmic Therapy. ### Management Hierarchy in HCM with VT/Syncope ``` HCM with PVCs/NSVT + Syncope + Family Hx SCD ↓ Beta-blocker (first-line antiarrhythmic) ↓ ICD implantation (SCD prevention — high-risk features present) ↓ If refractory arrhythmias → Add amiodarone or disopyramide ``` **Citation:** Harrison's Principles of Internal Medicine, 21st ed., Ch. 238 (Hypertrophic Cardiomyopathy); ACC/AHA 2020 Guidelines on HCM Management.