Tachycardia: implanted defibrillators decreased death.

Clinical bottom line (level 1b)

  1. Patients with myocardial infarction and asymptomatic ventricular tachycardia who had a defibrillator implanted, were more likely to be alive at 5 years than those given conventional therapy (NNT = 7 at 5 years) .
Moss et al: The New England Journal of Medicine 1996; 335: 1933-1940
Expires August 2004

The study

Unblinded ?concealed randomised trial with intention-to-treat
Setting: 32 hospital centres, 30 in USA and 2 in Europe

196 patients (aged mean 63 years, 94% male) Q-wave or enzyme positive myocardial infarction 3 weeks or more before entry with an episode of asymptomatic, unsustained ventricular tachycardia (a run of 3-30 ventricular ectopic beats at a rate >120 beats per minute)

Excluded if
  • <25 years old
  • > 80 years old
  • ejection fraction >0.35 (as assessed by angiography, radionuclide scanning or echocardiography)
  • NYHA heart failure class IV
  • coronary-artery bypass grafting within the past 2 months or coronary angioplasty within the past 3 months
  • one or more of: previous cardiac arrest or ventricular tachycardia causing syncope that was not associated with myocardial infarction; symptomatic hypotension while in a stable rhythm; myocardial infarction within the last 3 weeks
  • women of child-bearing age who were not using medically prescribed contraceptives
  • advanced cerebrovascular disease
  • any condition other than cardiac disease that was associated with a reduced likelihood of survival for the duration of the trial
  • participating in other trials


    • Note:
  • Half the patients received transthoracic devices, but later entry patients received transvenous implantation.


    • Control Group: (n = 101, 101 analysed): conventional therapy
    Experimental Group: (n = 95, 95 analysed): implantable defibrillator - testing was carried out during implantation to achieve defibrillation with a 10-J safety margin. Monophasic and biphasic pulse generators were used.
    The choice of conventional therapy, including the decision whether to use antiarrhythmic drugs, was left to the patient's attending physician. Drug therapy was used in both groups at the physician's discretion.
    98.5% followed for anywhere between 1 and 61 months

    The evidence

    Analysis based on Kapan-Meier survival curves
    Outcome Time to outcome CER RR
    (95% CI)    		 NNT
    (95% CI)
    death 5 years /
    (28%)    		 0.44
    (0.26 to 0.82)     		7
    (5 to 20)

    Analysis based on numbers of events and average follow-up
    Outcome Time to outcome CEREERRRR
    (95% CI)    		ARR
    (95% CI)    		NNT
    (95% CI)
    death unknown 39
    (38.6%)    		 15
    (15.8%)    		 59.0%
    (31.0% to 76.0%)    		 22.8%
    (10.8% to 34.8%)    		 4
    (3 to 9)

  • 11 patients in the conventional group crossed over to the defibrillator group due to an adverse drug reaction, and 5 in the defibrillator group crossed to the conventional group. Two patients had their defibrillators deactivated during the course of the trial.
  • No difference between the two methods of implantation (p=0.78)

    • Comments

    1. Uncertain duration of mean follow-up. Kaplan-Meier estimate based on a maximum follow-up of 5 years.

    Citation

    1. Moss AJ, Hall WJ, Cannom DS, et al: Improved survival with an implanted defibrillator in patients with coronary disease at high risk for ventricular arrhythmia. The New England Journal of Medicine 1996; 335: 1933-1940
    Contributor: Clare Wotton and Bob Phillips, August 1999
    Reviewer:

    Clinical Question.
    Patient myocardial infarction and tachycardia
    Intervention or Exposure defibrillator
    Comparison conventional therapy
    Outcome death