Cardiac arrest: amplitude of fibrillation affected outcome.

Clinical bottom line (level 2b)

  1. A third of patients who had an out-of hospital VF cardiac arrest die in hospital.
  2. Patients who suffered an out-of-hospital cardiac arrest and had fine ventricular fibrillation, were less likely to be discharged from hospital alive than those with a coarse fibrillation.
Weaver et al: Annals of Internal Medicine 1985; 102: 53-55
Expires October 2003

The study

Inception cohort study with objective outcomes, adjusted for confounding factors, not validated in an independent set of patients.

Setting: community, USA

394 patients (aged mean 65 years, % male) with a cardiac arrest due to ventricular fibrillation

Excluded if
  • presenting in asystole or electrical-mechanical dissociation



    • Factors studied:
  • initial rhythm, age, sex, amplitude of rhythm, delays
  • fine fibrillation < or = 0.2 mV


    • Following defibrillator-shock, patients were monitored with electrodes and amplitude was measured by the greatest peak-to-peak deflection observed in any sinusoidal wave occurring just before the first shock. Initial shocks were 175 J or 320 J delivered by random assignment.

    100% followed for discharge
    Outcomes studied:
  • death in hospital

    • The evidence

    outcome time to outcome number of patients/total number %
    (95% CI)    		 NNF
    (95% CI)
    death in hospital discharge 121/394 31%
    (26% to 35%)    		 3
    (3 to 4)

    prognostic factor for
    death in hospital     		time to outcome unadjusted RR
    (95% CI)    		 NNF+
    (95% CI)
    fine fibrillation discharge 1.46
    (1.32 to 1.62)     		3
    (3 to 5)

    prognostic factor outcome present outcome absent unadjusted RR
    (95% CI)    		 NNF+
    (95% CI)
    fine fibrillation 62 4 1.46
    (1.32 to 1.62)     		3
    (3 to 5)
    no fine fibrillation 59 269

    • Fine fibrillation remained an independent predictor of death following logistic regression analysis.

    Comments

    1. The data is taken from a randomised controlled trial comparing different defibrillator shock strengths.
    2. In the fine fibrillation group, the arrest was witnessed less often than in the coarse fibrillation group, and the period from collapse to initiation of life support was longer in the patients with fine fibrillation.

    Citation

    1. Weaver WD, Cobb LA, Dennis D, et al: Amplitude of ventricular fibrillation waveform and outcome after cardiac arrest. Annals of Internal Medicine 1985; 102: 53-55
    Contributor: Clare Wotton & Chris Ball, October 1999
    Reviewer: Dwight Peretz

    Clinical Question.
    Patient cardiac arrest due to ventricular fibrillation
    Intervention or Exposure
    Comparison amplitude of ventricular fibrillation
    Outcome mortality