By Ashley Starkweather, B.S. and Asher Kimchi M.D.

Frankfurt, Germany – Prophylactic use of implantable cardioverter-defibrillators in patients who have recently had an acute myocardial infarction was shown to not significantly reduce overall mortality. The results of the Defibrillator in Acute Myocardial Infarction Trial were published by Stefan H. Hohnloser, M.D., et. al, from J.W. Goethe University in Frankfurt, Germany, in the December 9, 2004 issue of the New England Journal of Medicine. While ICD therapy was associated with a reduction in the rate of death due to arrhythmia, this benefit was offset by an increase in mortality from nonarrhythmic causes. 

The first 6 to 12 months after myocardial infarction constitute a period during which there is a particularly high risk of death from arrhythmia, and few therapies have been effective in counteracting this risk. This study evaluated the possible benefit of prophylactic use of ICDs in this patient population. 

Patients aged 18 to 80 years were eligible for the study if they had recently had a myocardial infarction (6 to 40 days ago) and had a left ventricular ejection fraction of 0.35 or less. The also had to have a standard deviation of normal to normal RR intervals of 70msec or less or a mean heart rate of at least 80 bpm over a 24 hour period. 

Patients were randomly assigned in a 1:1 ratio to either receive implantation of an ICD or not. All patients received the best standard medical therapy, including ACE inhibitors, beta blockers, aspirin, and lipid lowering drugs, as appropriate. Patients in the ICD group underwent implantation within one week of randomization. 

Patients were followed for a maximum of 4 years, with the study taking place from April 1998 to September 2003. The primary outcome was death from any cause, with a secondary outcome being death from cardiac arrhythmia. 

During an average observation period of 30 +/- 13 months, 120 patients died, 62 in the ICD group and 58 in the control group (95 confidence interval, 0.76 to 1.55, two sided P=0.66). Death from arrhythmic causes was significantly lower in the treatment group, with an annual rate of 1.5 percent in the ICD group and 3.5 percent in the control group (95 percent confidence interval, 0.22 to 0.83, two-sided P=0.009). However, the death rate from cardiac, nonarrhythmic causes was significantly increased in the ICD group (P=0.05).  

These results show a statistically significant reduction (by more than 50 percent) in the risk of death due to arrhythmia in the ICD group; however, this effect was offset by a significant increase, of similar magnitude, in the rate of death from nonarrhythmic causes. The most likely explanation for this data is that patients “saved” from an arrhythmia related death by ICD therapy are also at high risk for death from other cardiac causes.  

However, the present data does not prove that ICDs reduce mortality post-acute myocardial infarction, despite the fact that they may decrease the risk of death from cardiac arrhythmia. 

Coauthors: Karl Heinz Kuck, M.D.; Paul Dorian, M.D.; Robin S. Roberts, M.Tech.; John R. Hampton, M.D., Robert Hatala, M.D.; Eric Fain, M.D.; Michael Gent, D.Sc., and Stuart J. Connolly, M.D.