Atrial fibrillation: acute: ibutilide was effective at cardioversion but increased the risk of VT.

Clinical bottom line (level 1b)

  1. Ibutilide was more effective than placebo at cardioversion in patients with acute onset atrial fibrillation or flutter (NNT = 2 at 1.5 hours) .
  2. Patients given ibutilide were at increased risk of ventricular tachycardia (NNH = 11 at 1.5 years) .
Stambler et al: Circulation 1996; 94 (7): 1613-1621
Expires December 2003

The study

Double-blinded concealed randomised trial without intention-to-treat
Setting: 21 acute hospitals, USA

266 patients (aged mean 67, 80% male) sustained atrial fibrillation or flutter for >3 hours and <45 days

Excluded if
  • <18 years old
  • child-bearing potential
  • weighed > 100 kg
  • history of torsade de points or a corrected QT interval >440 ms
  • received ibutilide previously
  • MI or cardiac surgery within 30 days
  • clinical evidence of digitalis toxicity or hyperthyroidism
  • haemodynamically unstable (systolic blood pressure <90 mmHg, diastolic bp >105 mmHg)
  • symptoms of angina or congestive heart failure
  • potassium <4.0 mmol/l, LFTs > twice upper limit of normal
  • antiarrhythmic drug taken within five half lives, unless beta-blocker, calcium channel blocker or digoxin


    • Note:
  • Patients with AF for more than three days required two weeks of anticoagulation before cardioversion was attempted.
  • Patients were stratified for type of arrhythmia before randomisation.


    • Control Group: (n = 86, 81 analysed): placebo
    Experimental Group: (n = 172, 161 analysed): ibutilide 1.0 mg iv over 10 minutes, followed by 0.5 or 1.0 mg iv over 10 minutes

    100% followed for 1.5 hours

    The evidence

    Outcome Time to outcome CEREERRRR
    (95% CI)    		ARR
    (95% CI)    		NNT
    (95% CI)
    no cardioversion 1.5 hours 79
    (97.5%)    		 86
    (53.4%)    		 45%
    (36% to 53%)    		 44.1%
    (35.7% to 52.5%)    		 2
    (2 to 3)
    polymorphic VT 24 hours 0
    (0.00%)    		 15
    (9.32%)    		 %
    (% to %)    		 -9.32%
    (-13.8% to -4.83%)    		 -11
    (-21 to -7)
    AF: no cardioversion 1.5 hours 79
    (97.5%)    		 56
    (69.1%)    		 29%
    (18% to 39%)    		 28.4%
    (17.8% to 39.0%)    		 4
    (3 to 6)
    flutter: no cardioversion 1.5 hours 79
    (97.5%)    		 30
    (37.5%)    		 62%
    (49% to 71%)    		 60.0%
    (48.9% to 71.2%)    		 2
    (1 to 2)

  • There was no clear difference in efficacy between the two dosing regimens.
  • Three patients with polymorphic VT required DC cardioversion.

    • Comments

    1. Ibutilide is a class III antiarrhythmic drug.

    Citation

    1. Stambler BS, Wood MA, Ellenbogen KA, et al: Efficacy and safety of repeated intravenous doses of ibutilide for rapid conversion of atrial flutter or fibrillation. Circulation 1996; 94 (7): 1613-1621
    Contributor: Chris Ball and Clare Wotton, December 2000
    Reviewer:

    Clinical Question.
    Patient AF or flutter
    Intervention or Exposure ibutilide
    Comparison placebo
    Outcome cardioversion, VT