Flecainide for Supraventricular Tachycardia
Flecainide is an effective second-line antiarrhythmic agent for SVT prevention in patients without structural or ischemic heart disease, achieving 85-93% efficacy rates, but catheter ablation remains the definitive first-line treatment. 1, 2
Patient Selection and Contraindications
Before considering flecainide, you must exclude structural heart disease and ischemic heart disease through appropriate cardiac imaging and stress testing, as flecainide is absolutely contraindicated in these populations due to increased mortality risk demonstrated in the CAST trial. 1, 2
Critical exclusion criteria include:
- Any structural heart disease 1, 3
- Ischemic heart disease or recent myocardial infarction 1, 3
- Bundle-branch block or intraventricular conduction delay 2
- Chronic atrial fibrillation (not adequately studied and not recommended) 3
Treatment Algorithm
First-Line Options
Beta-blockers, diltiazem, or verapamil should be tried first, as they have fewer conduction effects and Class I recommendations. 4, 1
Second-Line: Flecainide Indication
Flecainide receives a Class IIa recommendation (reasonable option) only when:
- First-line agents are ineffective or contraindicated 1
- Patient refuses or is not a candidate for catheter ablation 1
- No structural or ischemic heart disease confirmed 1
Definitive Treatment
Catheter ablation should be strongly considered as it provides definitive cure and avoids long-term medication risks and side effects. 4, 2
Efficacy Data by SVT Type
AVNRT (AV Nodal Reentrant Tachycardia):
- 30% achieve complete symptomatic suppression (superior to verapamil's 13%) 1
- 85% rendered non-inducible on electrophysiology study 1, 2
AVRT (AV Reentrant Tachycardia):
- 85% rendered non-inducible with sustained tachycardia 1
- Combination with beta-blockers increases efficacy to >90% 1
Paroxysmal SVT (general):
- Only 24% recurrence rate versus 85% on placebo 1
- 87% symptomatic improvement in clinical trials 5
- 93% probability of effective treatment (<2 attacks) over 12 months 2
Dosing and Administration
Initial dosing: 100 mg twice daily orally, can be increased by 50 mg twice daily every 4 days to maximum 200 mg twice daily. 5
Combination therapy: Adding a beta-blocker is recommended to enhance efficacy and prevent 1:1 AV conduction if atrial flutter develops. 1
Monitoring Requirements
Monitor for:
- Bradycardia (most common cardiac side effect requiring dose reduction) 4
- QRS widening (should not significantly increase; reduce dose if incomplete bundle branch block develops) 2, 6
- Proarrhythmic events (occurred in 3/151 patients in multicenter trial) 5
- Noncardiac effects: abnormal vision, dizziness, headaches (67% of patients, usually subside after 1-2 months) 5, 7
Common Pitfalls to Avoid
Do not use flecainide if:
- Patient has any degree of structural heart disease (cardiac adverse events occurred in 5/17 patients with structural disease in one trial) 5
- PR interval >200 ms or any conduction abnormalities present 2
- Patient has chronic atrial fibrillation (lowest efficacy at 56% and highest side effect rate) 5
Avoid extreme vagal maneuvers in patients on flecainide due to additive bradycardic effects, though teaching vagal maneuvers for acute termination remains appropriate. 4
Special Populations
Pediatric/Newborn use: Flecainide demonstrates 85% efficacy in newborns without structural heart disease at 2 mg/kg/day divided twice daily, with good safety profile when appropriately monitored. 6 Single oral doses (2.9 mg/kg) can terminate acute episodes in children with 88% success rate. 8
Long-Term Outcomes
Flecainide maintains efficacy during chronic therapy, with sustained benefit over mean follow-up of 17-26 months showing either maintained or improved arrhythmia control compared to initial treatment periods. 9, 7