What are the alternative medications for supraventricular tachycardia (SVT) treatment in an admission setting, aside from adenosine?

Alternative Medications for SVT in the Admission Setting

For stable SVT that fails to respond to adenosine or vagal maneuvers, use IV diltiazem (15-20 mg over 2 minutes) or IV verapamil (2.5-5 mg over 2 minutes) as your next-line agents, with beta-blockers as a reasonable alternative. 1

Primary Alternative Agents: Calcium Channel Blockers

Diltiazem and verapamil are the preferred alternatives to adenosine for acute SVT management in hemodynamically stable patients, with Class IIa recommendations from both AHA and ACC/AHA/HRS guidelines. 1

Diltiazem Dosing

• Initial dose: 15-20 mg (0.25 mg/kg) IV over 2 minutes 1
• If needed after 15 minutes: 20-25 mg (0.35 mg/kg) IV 1
• Maintenance infusion: 5-15 mg/hour, titrated to heart rate 1
• Conversion rate: 64-98% in clinical trials 1
• Recent data shows 82.4% conversion rate with median time of 6 minutes 2

Verapamil Dosing

• Initial dose: 2.5-5 mg IV over 2 minutes (3 minutes in elderly) 1
• Repeat doses: 5-10 mg every 15-30 minutes to maximum 20 mg 1
• Alternative regimen: 5 mg bolus every 15 minutes to maximum 30 mg 1
• Slow infusion (1 mg/min up to 20 mg) shows 98% conversion rate with minimal hypotension risk 3

Critical Safety Considerations for Calcium Channel Blockers

• Only use in narrow-complex SVT or rhythms definitively known to be supraventricular 1
• Absolutely contraindicated in wide-complex tachycardias (may be ventricular tachycardia) 1
• Avoid in patients with impaired ventricular function or heart failure 1
• Do not use in pre-excited atrial fibrillation (WPW syndrome) - may cause hemodynamic collapse or ventricular fibrillation 1
• Slow infusion over 20 minutes reduces hypotension risk compared to rapid bolus 1

Secondary Alternative: Beta-Blockers

IV beta-blockers are reasonable alternatives with Class IIa (diltiazem/verapamil) to Class IIb (beta-blockers alone) recommendations, though less effective than calcium channel blockers. 1

Available IV Beta-Blockers

• Metoprolol, atenolol, propranolol, esmolol, labetalol 1
• Esmolol was less effective than diltiazem in head-to-head trials 1
• Excellent safety profile despite lower efficacy 1
• Particularly useful in patients who cannot tolerate calcium channel blockers 1

Beta-Blocker Considerations

• Use cautiously with concurrent calcium channel blockers - risk of potentiated hypotension and bradycardia 1
• Safe in patients without structural heart disease 1
• May be combined with oral diltiazem for enhanced effect 1

Rescue and Special Situation Agents

For Adenosine-Refractory Cases

• Diltiazem successfully rescued 35% of adenosine failures in recent multicenter data 2
• Consider higher adenosine doses (24-36 mg) in consultation with cardiology before switching agents 4
• Dose adjustments needed for patients on theophylline, caffeine (increase dose) or dipyridamole, carbamazepine (decrease to 3 mg) 1

Amiodarone

• Reserved for refractory cases or when other agents contraindicated 1
• Slower onset than adenosine or calcium channel blockers 1
• Higher proarrhythmic risk compared to first-line agents 1
• Preferred in patients with impaired LV function or heart failure where calcium channel blockers contraindicated 1

For Pre-Excited Atrial Fibrillation (WPW)

• Ibutilide or IV procainamide are the agents of choice 1
• These slow accessory pathway conduction and may terminate AF 1
• Never use AV nodal blockers (diltiazem, verapamil, beta-blockers, adenosine) - can enhance accessory pathway conduction leading to ventricular fibrillation 1

Procainamide for Wide-Complex Tachycardia

• Recommended for stable wide-complex tachycardia of uncertain etiology 1
• Safer than calcium channel blockers when VT cannot be excluded 1

Oral Agents for Ongoing Management

Oral beta-blockers, diltiazem, or verapamil may be reasonable for acute treatment in stable patients, particularly those without IV access. 1

• Combination oral diltiazem plus propranolol shows success in terminating AVNRT/AVRT 1
• Can be administered alongside vagal maneuvers 1
• Useful for preventing recurrence after successful conversion 1

Common Pitfalls to Avoid

1. Never give calcium channel blockers for wide-complex tachycardia - assume VT until proven otherwise 1
2. Always have defibrillator available when treating SVT, especially with adenosine in possible WPW 1
3. Avoid combining IV calcium channel blockers and beta-blockers without careful monitoring 1
4. Don't use digoxin acutely - it enhances accessory pathway conduction in WPW and has slow onset 1
5. Monitor for conversion to atrial fibrillation after any agent - may require rate control strategy 1, 2

Algorithm for Medication Selection

1. First-line: Vagal maneuvers → Adenosine 6 mg → 12 mg → 12 mg 1
2. If adenosine fails or recurs:
   • Narrow-complex, stable, no heart failure → Diltiazem or verapamil 1
   • Heart failure present → Amiodarone 1
   • Pre-excitation visible → Avoid AV nodal blockers, consider procainamide 1
3. If calcium channel blockers fail: Beta-blockers or amiodarone 1
4. Hemodynamically unstable at any point: Synchronized cardioversion 1