What continuous medications can be used for Supraventricular Tachycardia (SVT) other than adenosine (adenosine) push for patients who experience recurrent episodes?

Continuous Medications for Recurrent SVT

For patients experiencing recurrent SVT episodes, beta-blockers (metoprolol or propranolol) or calcium channel blockers (diltiazem or verapamil) should be initiated as first-line continuous therapy, with flecainide or propafenone reserved as second-line options in patients without structural heart disease. 1, 2

First-Line Continuous Therapy

Beta-Blockers and Calcium Channel Blockers

• Beta-blockers (metoprolol, propranolol) or non-dihydropyridine calcium channel blockers (verapamil up to 480 mg/day, diltiazem) are the preferred initial agents for ongoing SVT management due to their excellent safety profile and effectiveness in preventing recurrent episodes 1, 2
• Verapamil has demonstrated efficacy in randomized trials, reducing both the number and duration of SVT episodes when used at doses of 360-480 mg/day 1
• These agents work by slowing AV nodal conduction, which is the critical component in most SVT mechanisms (AVNRT and AVRT) 1

Important Cautions with First-Line Agents

• Beta-blockers should be used cautiously in patients with severe bronchospastic disease 2, 3
• Calcium channel blockers require caution in patients with heart failure or hypotension 2
• Monitor for bradycardia, especially in patients with underlying sinus node dysfunction 2

Second-Line Continuous Therapy

Class IC Antiarrhythmics (Flecainide and Propafenone)

• Flecainide (100-300 mg/day) or propafenone (450-900 mg/day) are reasonable second-line options when beta-blockers or calcium channel blockers are ineffective or contraindicated, but only in patients without structural heart disease or ischemic heart disease 1
• Randomized trials demonstrate high efficacy: 86% probability of effective treatment with propafenone and 93% with flecainide over 12 months 1
• These agents are absolutely contraindicated in patients with structural heart disease or coronary artery disease due to increased mortality risk demonstrated in the CAST trial 1, 3
• Flecainide dosing should start at 50 mg every 12 hours and may be increased by 50 mg increments every 4 days, with maximum dose of 300 mg/day for SVT 4
• Propafenone is indicated specifically for prolonging time to recurrence of paroxysmal SVT associated with disabling symptoms 3

Third-Line Continuous Therapy

Class III Antiarrhythmics

• Sotalol (80-160 mg twice daily) may be reasonable as third-line therapy when first and second-line agents fail, and has the advantage of being usable in patients with structural heart disease unlike flecainide/propafenone 1
• Dofetilide may be reasonable in patients who cannot tolerate or have failed beta-blockers, calcium channel blockers, and class IC agents, showing 50% probability of complete symptomatic suppression over 6 months 1
• Both sotalol and dofetilide carry proarrhythmic risk and should be reserved for patients not candidates for catheter ablation 1

Amiodarone

• Oral amiodarone may be considered only as a last resort when all other agents are ineffective or contraindicated, given the significant toxicity and side effects with long-term therapy 1
• Evidence for amiodarone in SVT management is limited to small retrospective studies 1

Treatment Algorithm

1. Start with beta-blocker (metoprolol/propranolol) OR calcium channel blocker (verapamil/diltiazem) based on patient comorbidities 1, 2
2. If first-line fails and patient has NO structural/ischemic heart disease: Add or switch to flecainide or propafenone 1
3. If first-line fails and patient HAS structural/ischemic heart disease: Consider sotalol 1
4. If all above fail: Consider dofetilide or amiodarone 1
5. At any point if medical therapy inadequate: Refer for electrophysiology study and catheter ablation, which offers definitive cure 1, 2

Critical Pitfalls to Avoid

• Never use flecainide or propafenone in patients with any structural heart disease, coronary disease, or prior myocardial infarction - this carries significant mortality risk 1, 2, 3
• Do not use calcium channel blockers (verapamil/diltiazem) for wide-complex tachycardia of unknown origin, especially with history of myocardial dysfunction, as this could be ventricular tachycardia 1
• Avoid digoxin as monotherapy - while it may be reasonable in some cases, it should be reserved for patients who cannot take any other agents and must be used with caution regarding renal function and toxicity 1
• Do not initiate class IC agents (flecainide/propafenone) without confirming absence of structural heart disease through appropriate cardiac imaging 1

Special Considerations

• Patients should be educated on vagal maneuvers (Valsalva, ice-cold towel to face) as these can terminate episodes and reduce need for medical attention 1
• For patients with infrequent but prolonged episodes, "pill-in-the-pocket" single-dose therapy may be considered rather than continuous prophylaxis 1, 5
• Catheter ablation should be strongly considered as first-line definitive therapy given high success rates (>90%) and low complication rates, particularly for patients with frequent symptomatic episodes 1, 2