Atrial fibrillation: DC cardioversion: an initial shock of 360 J was more effective than lower energies

Clinical bottom line (level 1b)

  1. Patients with atrial fibrillation undergoing elective DC cardioversion who had an initial shock of 360 J were more likely to revert to sinus rhythm than with an initial shock of 100 J (NN T = 1 at minutes) or 200 J (NN T = 2 at minutes) .
  2. There was no difference in the overall success rate, but patients given 360 J received less cumulative energy (on average 200 J less) and fewer shocks (on average one fewer).
Joglar et al: American Journal of Cardiology 2000; 86 : 348-350
Expires November 2003

The study

Single-blinded ?concealed randomised trial with intention-to-treat
Setting: 2 acute hospitals, USA

64 patients (aged mean 62, 72% male) with atrial fibrillation for > 48 hours referred for elective cardioversion

Excluded if
  • recent myocardial infarction or surgery within previous 14 days
  • presence of epicardial implantable defibrillator system
  • active pericarditis
  • neuromuscular disease

    Control Group: (n = 21, 21 analysed): initial shock: 100 J. If this failed then 200 J, 360 J, and 360 J in sternum/apex position.
    Experimental Group: (n = 23, 23 analysed): initial shock: 200 J. If this failed 360 J, then 360 J in sternum/apex position
    Experimental Group: (n = 20, 20 analysed): initial shock: 360J. If this failed, 360J in sternum/apex position
    All patients were anticoagulated (INR 2.0 to 3.0) for 3 weeks before cardioversion, or underwent transoesophageal echocardiography to rule out left atrial thrombus, followed by anticoagulation during and after cardioversion
    100% followed for - minutes

    The evidence

    200 J v. 100 J
    Outcome Time to outcome CER EER RRR
    (95% CI)    		 ARR
    (95% CI)    		 NNT
    (95% CI)
    sinus rhythm after initial shock minutes 3
    (14.3%)    		 9
    (39.1%)    		 170%
    (-15% to 780%)    		 24.8%
    (-0.092% to 49.8%)    		 4
    (NNT = 2 to infinity;
    NNH = 1100 to infinity)

    360 J v. 100 J
    Outcome Time to outcome CER EER RRR
    (95% CI)    		 ARR
    (95% CI)    		 NN T
    (95% CI)
    sinus rhythm after initial shock minutes 3
    (14.3%)    		 19
    (95.0%)    		 570%
    (130% to 1800%)    		 80.7%
    (63.0% to 98.5%)    		 1
    (1 to 2)

    360 J v. 200 J
    Outcome Time to outcome CER EER RRR
    (95% CI)    		 ARR
    (95% CI)    		 NN T
    (95% CI)
    sinus rhythm after initial shock minutes 23
    (39.1%)    		 19
    (95.0%)    		 140%
    (44% to 310%)    		 55.9%
    (33.8% to 78.0%)    		 2
    (1 to 3)

    Outcome Control Group
    (SD)    		 Experimental Group
    (SD)    		 Mean Difference
    (95% CI)
    number of shocks: 360 J v. 100 J 2.81
    (1.17)     		1.15
    (0.49)     		1.7
    (1.1 to 2.2)
    cumulative energy delivered: 360 J v. 100 J 615
    (385)     		414
    (176)     		200
    (10 to 390)

  • The amount of energy or number of shocks delivered was not significantly different between the 100 J and 200 J groups.
  • There was no significant difference in overall success rate between the three groups (90%, 90%, 100% respectively).

    Comments

    1. Paddles were placed in an anterior-posterior position
    2. None of the patients who received high-energy shocks had elevated troponin I levels 24 hours later.

    Citation

    1. Joglar JA, Hamdan MH, Ramaswamy K, et al: initial energy for elective external cardioversion of persistent atrial fibrillation. American Journal of Cardiology 2000; 86 : 348-350
    Search Terms: from ACP Journal Club other articles noted
    Contributor: Chris Ball, November 2001
    Reviewer:

    Clinical Question.
    Patient atrial fibrillation
    Intervention or Exposure energy for DC cardioversion
    Outcome sinus rhythm