What is the next step for a patient who did not convert with intravenous (IV) adenosine?

Management After Failed Adenosine for Supraventricular Tachycardia

For patients who fail to convert with IV adenosine, the next step should be administration of a calcium channel blocker such as verapamil or diltiazem. 1, 2

Treatment Algorithm After Failed Adenosine

1. Calcium Channel Blockers (First Choice)

   • Verapamil: 2.5-5 mg IV bolus over 2 minutes (3 minutes in older patients)
     • If no response and no adverse effects, can repeat with 5-10 mg every 15-30 minutes up to total dose of 20 mg
     • Alternative regimen: 5 mg bolus every 15 minutes up to total 30 mg 1
   • Diltiazem: 15-20 mg (0.25 mg/kg) IV over 2 minutes
     • If needed, give additional 20-25 mg (0.35 mg/kg) IV after 15 minutes
     • Maintenance infusion: 5-15 mg/hour, titrated to heart rate 1

2. Beta-Blockers (Alternative Option)

   • Various IV beta-blockers can be used including metoprolol, atenolol, propranolol, esmolol, or labetalol 1
   • Recommended with Class IIa, LOE C-LD by American Heart Association 2

Efficacy Considerations

• Calcium channel blockers have demonstrated conversion rates of 64-98% for SVT 2
• Some studies show calcium channel blockers may have higher conversion rates (98%) compared to adenosine (86.5%) 3
• Slow infusion of calcium channel blockers has been shown to be safe with minimal risk of hypotension 3

Important Contraindications and Precautions

Avoid Verapamil in:

• Wide-complex tachycardias of uncertain origin
• Impaired ventricular function or heart failure
• Patients with suspected systolic heart failure 2
• Pre-excited atrial fibrillation 2

Avoid Beta-Blockers in:

• Severe conduction abnormalities
• Sinus node dysfunction
• Bronchospastic disease 2

Special Considerations

• Hemodynamically Unstable Patients: If the patient shows signs of hemodynamic instability (hypotension, altered mental status, signs of shock, severe chest pain), proceed directly to synchronized cardioversion rather than medication 2

• Wolff-Parkinson-White (WPW) Syndrome: Have a defibrillator available when administering adenosine to patients with suspected WPW due to risk of initiating atrial fibrillation with rapid ventricular rates 1

• Pregnancy: Vagal maneuvers and adenosine are preferred first-line treatments; calcium channel blockers can be considered if these fail 2

• Heart Failure: Avoid verapamil and diltiazem; consider amiodarone as an alternative 1, 2

Common Pitfalls to Avoid

• Failing to recognize when a patient requires immediate electrical cardioversion rather than pharmacological treatment
• Using verapamil in patients with wide-complex tachycardias of unknown origin
• Not having resuscitation equipment available when administering antiarrhythmic medications
• Administering calcium channel blockers too rapidly, which increases risk of hypotension

By following this algorithm, most cases of supraventricular tachycardia that fail to respond to adenosine can be successfully managed with calcium channel blockers or beta-blockers, with electrical cardioversion reserved for refractory cases or hemodynamically unstable patients.