What is the recommended use and dosage of Corvert (ibutilide) for converting atrial fibrillation or atrial flutter to a normal sinus rhythm?

Corvert (Ibutilide) for Conversion of Atrial Fibrillation or Atrial Flutter

Intravenous ibutilide (Corvert) is recommended at a dose of 1 mg administered over 10 minutes, with a possible second 1 mg dose after waiting 10 minutes if the first dose is unsuccessful, for converting atrial fibrillation or atrial flutter to normal sinus rhythm. 1, 2

Dosage Recommendations

• Standard adult dosing:

  • 1 mg IV administered over 10 minutes
  • If arrhythmia persists 10 minutes after completion of the first infusion, a second 1 mg dose may be given 1

• Weight-based dosing (for patients < 60 kg):

  • 0.01 mg/kg IV over 10 minutes
  • May repeat once if necessary after waiting 10 minutes 1, 2

Efficacy by Arrhythmia Type

Ibutilide demonstrates different efficacy rates depending on the type of arrhythmia:

• Atrial flutter: 50-70% conversion rate (higher efficacy) 2, 3
• Atrial fibrillation: 30-50% conversion rate 2, 3

Most conversions (approximately 70%) occur within 30 minutes of starting the infusion 2.

Patient Selection and Considerations

Ideal Candidates

• Recent-onset arrhythmias (patients with arrhythmias of shorter duration respond better)
• Response rates of 42-50% for arrhythmias <30 days vs. 16-31% for chronic arrhythmias 2
• Patients with atrial flutter (higher success rate than with atrial fibrillation) 2, 3

Contraindications

• Prolonged QT interval (uncorrected QT >440 ms) 1
• Hypokalemia or hypomagnesemia (should be corrected before administration) 3
• Severe hepatic impairment (drug is metabolized in the liver) 4
• Severe aortic stenosis 1
• Recent acute coronary syndrome (<30 days) 1
• NYHA Class III and IV heart failure 1
• Systolic blood pressure <100 mmHg 1

Monitoring and Safety Precautions

1. Continuous ECG monitoring is mandatory during administration and for at least 4 hours afterward or until QTc returns to baseline 3

2. Proarrhythmic risk:

   • QT prolongation and torsades de pointes are the most serious adverse effects
   • Nonsustained polymorphic VT occurs in 2.7-6.7% of patients
   • Sustained polymorphic VT occurs in approximately 1.7% of patients 4, 3

3. Required equipment during administration:

   • External cardiac defibrillator
   • IV magnesium (for treating torsades de pointes)
   • External transcutaneous cardiac pacemaker 3

4. Electrolyte management:

   • Correct hypokalemia and hypomagnesemia before administration
   • Consider prophylactic magnesium administration 3, 5

Comparison with Other Antiarrhythmic Agents

Ibutilide has been shown to be more effective than:

• Procainamide (76% vs. 14% for atrial flutter; 51% vs. 21% for atrial fibrillation) 6
• Sotalol (70% vs. 19% for atrial flutter; 44% vs. 11% for atrial fibrillation) 2

It can also be effective in patients where amiodarone has failed, with conversion rates of approximately 81.5% in such cases 5.

Anticoagulation Considerations

Anticoagulation should be managed according to the duration of the arrhythmia:

• AF/flutter <48 hours with high stroke risk: IV heparin, LMWH, or direct oral anticoagulant before or immediately after cardioversion 1

• AF/flutter ≥48 hours or unknown duration: Anticoagulate with warfarin for at least 3 weeks before and 4 weeks after cardioversion, OR perform TEE to rule out left atrial thrombus before cardioversion 1

• Long-term anticoagulation should be based on thromboembolic risk (CHA₂DS₂-VASc score), not on whether sinus rhythm is maintained 1, 7

Common Pitfalls to Avoid

1. Failure to monitor QT interval before and during treatment
2. Not correcting electrolyte abnormalities before administration
3. Inadequate monitoring after infusion (minimum 4 hours required)
4. Using in contraindicated populations (severe heart failure, prolonged QT)
5. Not having resuscitation equipment immediately available
6. Inadequate anticoagulation before and after cardioversion

Ibutilide is a valuable option for pharmacological cardioversion of atrial fibrillation and flutter, particularly for recent-onset arrhythmias, with proper patient selection and monitoring.