As a healthy 67‑year‑old male with supraventricular tachycardia (SVT), should I be concerned about the side effects of flecainide?

Should You Be Concerned About Flecainide Side Effects?

As a healthy 67-year-old male with SVT and no structural heart disease, flecainide is a reasonable and generally safe treatment option for you, but you should be aware of specific side effects—particularly visual disturbances and dizziness—and understand that your "healthy" status must be confirmed to exclude any structural heart disease or coronary artery disease before starting this medication. 1, 2

Critical Safety Considerations Before Starting Flecainide

Absolute Requirements for Safe Use

You must meet ALL of the following criteria to safely use flecainide 1, 2:

• No structural heart disease (no prior heart attack, no heart failure, normal heart function)
• No coronary artery disease or ischemic heart disease
• No history of myocardial infarction
• Normal left ventricular ejection fraction
• No significant sinus node or AV conduction disease (unless you have a pacemaker)

The reason this matters: Flecainide increases mortality and causes dangerous ventricular arrhythmias in patients with structural heart disease or prior heart attacks. 1, 3, 4 This was definitively shown in the CAST trial, which found increased deaths in post-MI patients. However, this risk does NOT apply to patients like you who have SVT without structural heart disease. 4, 5

What "Healthy" Really Means in This Context

Before your physician prescribes flecainide, you should have 2:

• Echocardiogram to confirm normal heart structure and function
• ECG to rule out conduction abnormalities, bundle branch blocks, or QT prolongation
• Assessment for coronary disease (especially at age 67, given cardiac risk factors)
• Kidney function testing (flecainide is eliminated through kidneys) 1, 2

Expected Side Effects You Should Anticipate

Common Non-Cardiac Side Effects (Occur in 10-20% of Patients)

The most frequent side effects you're likely to experience are 3, 5:

• Visual disturbances (16% of patients): Blurred vision, difficulty focusing, spots before eyes 3
• Dizziness (19% of patients): Lightheadedness, unsteadiness, near-syncope 3
• Headache (10%) 3
• Nausea (9%) 3
• Fatigue (8%) 3

Important context: These side effects are typically mild, transient, and tolerable. 4 In clinical trials of SVT patients, 64-67% reported at least one non-cardiac side effect, but most continued treatment successfully. 5 Only about 5% of patients discontinue flecainide due to non-cardiac side effects. 3

Cardiac Side Effects (Less Common but More Serious)

The cardiac risks you should monitor for include 1, 3:

• Proarrhythmia (new or worsened arrhythmias): Risk is approximately 3% in SVT patients without structural heart disease 5
• Atrial flutter with rapid 1:1 AV conduction: Flecainide can convert atrial fibrillation to atrial flutter that conducts rapidly to the ventricles 1, 2
• Conduction abnormalities: Bradycardia, heart block (0.5-1.2% risk) 3
• QRS widening: An increase >25% from baseline indicates potential toxicity 2

Critical safety measure: You should typically receive a beta-blocker or calcium channel blocker (like diltiazem or verapamil) along with flecainide to prevent rapid ventricular rates if atrial flutter develops. 2

Specific Monitoring Requirements

Initial Monitoring

When starting flecainide, expect 1, 2:

• Starting dose: 50 mg twice daily 1
• Dose titration: Can increase by 50 mg every 4 days up to maximum 200 mg twice daily 1
• ECG monitoring: Check QRS duration—if it widens by >25%, dose reduction is needed 2
• Most proarrhythmic events occur within the first 14 days 3

Ongoing Monitoring

During long-term treatment 2, 6:

• Regular ECGs to monitor QRS duration
• Kidney function tests (especially important at your age)
• If you have a pacemaker or defibrillator, device settings may need adjustment (flecainide increases pacing thresholds and defibrillation energy requirements) 2

Drug Interactions You Must Avoid

Flecainide has significant interactions with 1, 2:

• Amiodarone (increases flecainide levels—requires dose reduction)
• Digoxin (flecainide increases digoxin levels by 15-25%)
• Verapamil (increases flecainide levels—requires monitoring)
• Certain antibiotics: Clarithromycin, erythromycin
• Antifungals: Itraconazole, voriconazole, posaconazole

Your Risk Profile as a 67-Year-Old

Age-specific considerations 1, 2:

• At 67, kidney function naturally declines—this affects flecainide elimination and may require dose adjustment 1
• Coronary disease becomes more prevalent with age—ensure thorough cardiac evaluation before starting 2
• You're more likely to be on other medications that could interact with flecainide 1

Efficacy Data for SVT

What you can expect for effectiveness 5, 6:

• 87% of SVT patients improve symptomatically on flecainide 5
• 85-90% effectiveness rate for preventing recurrent SVT 1
• Long-term success: 87% of patients remain SVT-free over an average 3.9-year follow-up 6
• 30% report complete absence of tachycardia 1

When Flecainide Should NOT Be Used

Absolute contraindications that would make flecainide dangerous for you 1, 2:

• Significant ventricular dysfunction
• History of heart attack
• Structural heart disease
• Decompensated heart failure
• Second or third-degree AV block (without pacemaker)
• Brugada syndrome

Alternative Considerations

If you're concerned about flecainide's side effects, discuss these alternatives with your physician 1:

• Beta-blockers, diltiazem, or verapamil: First-line options with favorable side effect profiles, effective in ~50% of SVT patients 1
• Catheter ablation: 93-95% success rate with 3% major complication risk—may be preferable to lifelong medication 1
• Propafenone: Similar efficacy and side effect profile to flecainide 1

Bottom Line for Your Situation

Flecainide is appropriate for you IF and ONLY IF you truly have no structural heart disease. 2, 4 The side effects—primarily visual disturbances and dizziness—are common but usually tolerable and don't require stopping the medication. 4, 5 The serious cardiac risks that made headlines from the CAST trial do not apply to SVT patients without structural heart disease. 4 Your main concerns should be: (1) ensuring thorough cardiac evaluation confirms you're truly "healthy" from a structural standpoint, (2) monitoring for QRS widening on ECG, and (3) having concurrent AV nodal blocking therapy to prevent rapid atrial flutter conduction. 1, 2