What is the recommended dosing of isoproterenol (beta-adrenergic agonist) for a patient with Brugada syndrome experiencing a ventricular tachycardia (VT) storm?

Isoproterenol Dosing for VT Storm in Brugada Syndrome

For patients with Brugada syndrome experiencing ventricular tachycardia storm, isoproterenol should be administered as a 1-2 μg bolus followed by continuous infusion at 0.15 μg/min. 1

Rationale and Mechanism of Action

Isoproterenol is a beta-adrenergic agonist that effectively suppresses ventricular arrhythmias in Brugada syndrome through several mechanisms:

• Increases heart rate (shortens RR interval)
• Decreases ST-segment elevation in right precordial leads
• Counteracts the ionic imbalance responsible for the Brugada ECG pattern
• Suppresses the arrhythmogenic substrate that triggers VT/VF

Administration Protocol

1. Initial bolus: 1-2 μg IV push
2. Continuous infusion: 0.15 μg/min (approximately 0.003 μg/kg/min)
3. Duration: Typically 1-3 days, with some cases requiring up to 24 ± 13 days 1, 2
4. Monitoring: Continuous ECG monitoring to observe:
   • Reduction in ST-segment elevation
   • Suppression of ventricular arrhythmias
   • Heart rate response

Clinical Efficacy

Isoproterenol has demonstrated excellent efficacy in suppressing VT storm in Brugada syndrome:

• Immediate suppression of arrhythmic storm after bolus administration 1
• Complete suppression of electrical storm in all treated patients in clinical studies 2
• Class IIa recommendation (Level of Evidence: C) by ACC/AHA/ESC guidelines 3

Transition to Chronic Therapy

After successful suppression of VT storm with isoproterenol:

• Transition to oral medications is typically possible
• Options for chronic therapy include:
  • Quinidine (preferred oral agent)
  • Denopamine
  • Cilostazol
  • Bepridil (alone or in combination)

Important Considerations and Pitfalls

1. Avoid beta-blockers: Unlike in other channelopathies, beta-blockers are potentially harmful in Brugada syndrome and should be avoided 4

2. Medication alternatives: If isoproterenol is unavailable or ineffective:

   • Quinidine is a reasonable alternative for electrical storm (Class IIb recommendation) 3
   • Radiofrequency catheter ablation may be considered for drug-resistant cases 5

3. Monitoring requirements:

   • Continuous cardiac monitoring is essential
   • Monitor for potential side effects of isoproterenol (tachycardia, hypotension, tremor)
   • Watch for recurrence of arrhythmias upon discontinuation

4. Long-term management:

   • ICD implantation remains the gold standard for high-risk Brugada patients 4
   • Isoproterenol is used as acute therapy, not for chronic management

5. Recurrence risk: Studies show approximately 6.1% risk of ES recurrence even after successful treatment 6

Algorithm for Management of VT Storm in Brugada Syndrome

1. Recognize VT storm in Brugada syndrome patient
2. Administer isoproterenol: 1-2 μg bolus followed by 0.15 μg/min infusion
3. Continue infusion for 1-3 days while monitoring for arrhythmia suppression
4. If successful, transition to oral therapy (quinidine preferred)
5. If unsuccessful, consider alternative approaches (higher dose isoproterenol, quinidine, or catheter ablation)

This approach has been shown to be highly effective, with studies demonstrating complete suppression of electrical storm in all treated patients 2.