Cardioversion: anticoagulation reduced embolic events.

Clinical bottom line (level 4)

  1. Patients who were anticoagulated before undergoing cardioversion for atrial fibrillation or flutter, were less likely to have embolic events subsequently (NNT = 45 at 6 weeks) .
Zeiler Arnold et al: Journal of the American College of Cardiology 1992; 19 (4): 851-855
Expires June 2004

The study

Retrospective cohort study with unblinded, unobjective outcomes, not adjusted for confounding factors, not validated in an independent set of patients.
Setting: university hospital, USA

428 patients (aged range 21 to 88 years; mean 64, 69% male) undergoing 454 elective DC cardioversions for atrial fibrillation (73%) or atrial flutter (lasting >48 hours)

Excluded if
  • unsuccessful cardioversion
  • cardioversion performed in patient's room or on ITU


    • Control Group: (n = 269, 269 analysed): no anticoagulation
    Experimental Group: (n = 185, 185 analysed): anticoagulation

    100% followed for 6 weeks

    The evidence

    Outcome Time to outcome CEREERRRR
    (95% CI)    		ARR
    (95% CI)    		NNT
    (95% CI)
    embolism 6 weeks 6
    (2.23%)    		 0
    (0.00%)    		 100%
    (% to %)    		 2.23%
    (0.47% to 4.00%)    		 45
    (25 to 220)

  • 628 cardioversions were performed during the study period- 72% were analysed.
  • Four patients had strokes, one had a peripheral embolism and one a pulmonary embolism; all within seven days of the procedure.
  • No patient with atrial flutter had an embolic event.

    • Comments

    1. No data was given on bleeding complication was given or anticoagulation used.
    2. Failure to adjust for confounding factors combined with unblinded outcomes (with no clear diagnostic definitions) makes these results much less certain.

    Citation

    1. Zeiler Arnold A, Mick MJ, Mazurek RP, et al: Role of prophylactic anticoagulation for direct current cardioversion in patients with atrial fibrillation or atrial flutter. Journal of the American College of Cardiology 1992; 19 (4): 851-855
    Contributor: Chris Ball and Clare Wotton, June 2000
    Reviewer:

    Clinical Question.
    Patient undergoing elective cardioversion for atrial flutter or fibrillation
    Intervention or Exposure anticoagulation
    Comparison no anticoagulation
    Outcome embolism