Is a beta blocker a better choice than amiodarone for a patient with decreased Left Ventricular Ejection Fraction (LVEF) who has spontaneously converted from Paroxysmal Supraventricular Tachycardia (PSVT) to sinus rhythm?

Beta-Blockers Are the Preferred Choice for PSVT with Reduced LVEF After Spontaneous Conversion

In a patient with decreased LVEF who has spontaneously converted from PSVT to sinus rhythm, beta-blockers are the superior choice over amiodarone for rhythm maintenance. This recommendation is based on the established safety profile of beta-blockers in heart failure, their proven efficacy in preventing arrhythmia recurrence, and the avoidance of amiodarone's significant toxicity burden in a patient who has already achieved sinus rhythm without it.

Primary Rationale: Safety in Heart Failure

Amiodarone and dofetilide are the only antiarrhythmic drugs with proven safety in patients with heart failure and reduced ejection fraction 1. However, this recommendation applies specifically to patients requiring pharmacological cardioversion or those with atrial fibrillation requiring rhythm control 1.

For a patient who has already spontaneously converted to sinus rhythm:

• The immediate need for amiodarone's cardioversion properties is eliminated 2
• Beta-blockers provide effective rhythm maintenance without amiodarone's toxicity profile 1
• Beta-blockers offer additional mortality benefit in heart failure patients with reduced LVEF 3

Beta-Blocker Efficacy for Rhythm Maintenance

Beta-blockers demonstrate moderate but consistent efficacy in preventing recurrence of supraventricular arrhythmias 1:

• Metoprolol, atenolol, and bisoprolol reduce the frequency and duration of paroxysmal supraventricular arrhythmias 1
• Beta-blockers reduce the risk of early recurrence after cardioversion 1
• They provide effective rate control if arrhythmia recurs, limiting hemodynamic consequences 1
• Beta-blockers are first-line therapy for supraventricular tachyarrhythmias 3

Amiodarone's Toxicity Profile

Amiodarone carries substantial long-term toxicity that is not justified when the patient has already achieved sinus rhythm spontaneously 4, 5:

• Pulmonary fibrosis and pulmonary toxicity 4
• Hepatic injury 4
• Thyroid dysfunction 5
• Bradycardia and heart block 4
• QT prolongation with risk of torsades de pointes 4
• 18% of patients discontinue amiodarone due to side effects after a mean of 468 days 1, 6

Amiodarone is generally reserved as a "drug of last resort" in the United States due to these serious noncardiac side effects 5.

When Amiodarone Would Be Appropriate

Amiodarone should be considered in this clinical scenario only if:

• The patient has recurrent PSVT despite beta-blocker therapy 1
• The patient has concomitant atrial fibrillation requiring rhythm control 1, 6
• Beta-blockers are contraindicated or not tolerated 1

In the SAFE-T trial, amiodarone showed superior rhythm maintenance compared to sotalol (median time to recurrence 487 days vs 74 days), but this advantage must be weighed against toxicity 1, 6.

Clinical Algorithm for This Patient

Step 1: Initiate beta-blocker therapy (metoprolol, carvedilol, or bisoprolol) for rhythm maintenance and heart failure management 1, 3

Step 2: Monitor for arrhythmia recurrence over 3-6 months 1

Step 3: If PSVT recurs despite beta-blocker therapy, then consider:

• Optimizing beta-blocker dose 3
• Adding or switching to amiodarone if recurrence is frequent or symptomatic 1, 6
• Catheter ablation for definitive treatment 3

Critical Pitfall to Avoid

Do not initiate amiodarone prophylactically in a patient who has spontaneously converted and has not yet failed beta-blocker therapy. The risk-benefit ratio strongly favors beta-blockers as first-line therapy in this setting, reserving amiodarone for refractory cases 1, 4, 5. Amiodarone's toxicity profile requires that it be used only when simpler, safer alternatives have been exhausted or when the clinical situation demands its unique properties (such as active cardioversion or refractory arrhythmias) 4, 5.