What is the role of Flecainide (antiarrhythmic medication) in the treatment of Supraventricular Tachycardia (SVT)?

Role of Flecainide in Supraventricular Tachycardia Treatment

Flecainide is recommended as a second-line agent for ongoing management of SVT in patients without structural heart disease who are not candidates for catheter ablation or in whom first-line agents (beta blockers, diltiazem, or verapamil) are ineffective or contraindicated. 1

Treatment Algorithm for SVT

First-Line Therapy

1. Catheter ablation - Most effective definitive treatment with high success rates (93-95%) and low complication rates (3%) 1
2. Pharmacological therapy:
   • Beta blockers, diltiazem, or verapamil - First-line medications for ongoing management in patients without pre-excitation 1
   • Vagal maneuvers - Should be taught to all patients for acute management 1, 2

Second-Line Therapy (When First-Line Fails or Is Contraindicated)

• Flecainide - For patients without structural heart disease 1, 3
  • Initial dose: 50 mg twice daily
  • Can be increased in 50 mg increments every 4 days
  • Maximum dose: 300 mg/day 2
  • Efficacy: 85-90% effective in preventing recurrent episodes 1
  • Complete suppression in 65% of patients; >90% when combined with a beta-blocker 2

Mechanism of Action and Efficacy

Flecainide belongs to the Class IC antiarrhythmic agents that:

• Block sodium channels, slowing conduction through the heart 3
• Directly slow or block conduction over accessory pathways 1
• Have local anesthetic activity 3

Indications for Flecainide in SVT

Flecainide is FDA-approved for:

• Paroxysmal supraventricular tachycardias (PSVT), including:
  • Atrioventricular nodal reentrant tachycardia (AVNRT)
  • Atrioventricular reentrant tachycardia (AVRT)
  • Other SVTs of unspecified mechanism with disabling symptoms 3

Contraindications and Cautions

1. Absolute contraindications:

   • Structural heart disease 1, 2, 3
   • Recent myocardial infarction 3
   • Significant ventricular dysfunction 1
   • Congenital heart disease with ventricular dysfunction 1

2. Monitoring requirements:

   • QRS widening should not exceed 150% of pretreatment QRS duration 2
   • Consider exercise testing to detect QRS widening at rapid heart rates 2
   • Monitor for proarrhythmic effects, especially in the first 48-72 hours 4
   • Therapeutic plasma levels: 0.2-1.0 mcg/mL 3

Special Considerations

Combination Therapy

• Adding a beta-blocker to flecainide:
  • Increases efficacy (>90% success rate) 2
  • Reduces risk of 1:1 conduction if atrial flutter occurs 2
  • Recommended when initiating flecainide therapy 2

Proarrhythmic Risk

Flecainide has a narrow therapeutic window and can cause proarrhythmic effects even at therapeutic doses 4, 5:

• Risk is higher in patients with structural heart disease 6
• Can cause ventricular arrhythmias, including sustained ventricular tachycardia 5
• Regular ECG monitoring is essential, even with subjective improvement 5

Long-Term Efficacy

Long-term studies show maintained or improved efficacy during chronic therapy:

• 82% of SVT patients remained free of arrhythmic attacks during long-term therapy 7
• 68% of atrial fibrillation patients remained free of arrhythmic attacks 7

Alternative Second-Line Agents

When flecainide is contraindicated or ineffective:

1. Sotalol - Can be used in patients with structural heart disease 1
2. Dofetilide - Alternative for patients with structural heart disease 1
3. Amiodarone - Reserved for patients who have failed other therapies due to significant long-term toxicity 1

Practical Approach to Flecainide Use

1. Confirm absence of structural heart disease before initiating therapy
2. Start at low dose (50 mg twice daily) and titrate gradually
3. Monitor ECG regularly for QRS widening and QT prolongation
4. Consider combination with beta-blocker for enhanced efficacy and safety
5. Educate patients about potential side effects (dizziness, visual disturbances, headaches) 6

Flecainide is highly effective for SVT management in appropriately selected patients without structural heart disease, but careful patient selection and monitoring are essential to minimize proarrhythmic risks.