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Patients who have suffered a myocardial infarction are
at risk of sudden cardiac death. The CAST study1 has
definitely shown that antiarrhythmic therapy with class I drugs is even accompanied with a
higher mortality. This adverse effect is not due to patient selection alone but also due
to an inadequate antiarrhythmic drug control. Rather, the only reason appears to be that
the unfavorable antiarrhythmic effects outweigh the beneficial ones. Treatment of
postinfarction patients with class I antiarrhythmics is thus no longer justified. Just as
disappointing is the outcome of the two large amiodarone studies2,3,
especially in view of the promising results of earlier smaller studies4,5.
In both studies, EMIAT and CAMIAT, overall mortality was the same in the amiodarone group
and in the placebo group.
It is therefore only natural to look for alternative treatment options in
postinfarction patients. Encouraged by the high incidence of arrhythmic events in
postinfarction patients, who were inducible and nonsuppressible during programmed
ventricular stimulation (PVS)6, the MADIT trial was
initiated7. The study included 196 patients with a
previous myocardial infarction, a left ventricular ejection fraction < 35%, a
documented episode of asymptomatic nonsustained ventricular tachycardia, and
nonsuppressible ventricular tachyarrhythmia during PVS. Ninety-five patients randomly
received an implantable defibrillator (ICD), the other 101 patients underwent
antiarrhythmic drug therapy. During the subsequent 27-month follow-up period, 39 deaths
occurred in the conventionally treated patients and 15 deaths in the ICD groups. These
results clearly indicate a favorable clinical outcome follow-up period, 39 deaths occurred
in the conventionally treated patients and 15 deaths in the ICD groups. These results
clearly indicate a favorable clinical outcome in high-risk myocardial infarction patients
treated by an ICD compared to those undergoing antiarrhythmic drug treatment.
The conclusion to be drawn from these results might be that myocardial infarction
patients with a comparable risk profile should in the future undergo prophylactic
implantation of an ICD. Why is there such reluctance about the MADIT results?
1. MADIT is not a postinfarction study in the proper sense of the term. Although all
study patients had a history of myocardial infarction, the event had occurred more than 6
months earlier in 75% of the cases. Only few of the patients were classic postinfarction
patients, ie patients with recent myocardial infarction and who typically undergo risk
stratification 7-14 days after the acute event. This is the time when the patients are
still in hospital and can undergo examinations for risk assessment including programmed
ventricular stimulation on a routine basis and at relatively low extra cost.
2. The study population is small; patient inclusion was stopped immediately after the
level of significance according to the statistical design of the study was reached.
Questions remain open as a result of the mismatch between the two groups regarding other
parameters (eg, beta-blocker treatment). Because of the small sample size subgroup
analysis is limited.
3. The kind of risk stratification performed in the MADIT trial is extremely
time-consuming and thus hardly feasible in a routine clinical setting. 1625 consecutive
myocardial infarction patients would have to be screened and stratified in order to select
3 (0.18%) patients who fulfill the MADIT criteria (EF ¾ 35%, nonsustained VT during
Holter ECG, inducible and nonsuppressible ventricular tachyarrhythmias during programmed
ventricular stimulation) 8. For many patients, this procedure involves considerable
physical stress, especially if performed repeatedly.
It will be the aim of future studies:
1. to find methods of risk stratification that are highly sensitive and allow
identification of patients already in the early postinfarction phase and
2. to investigate the benefit of prophylactic ICD implantation in the high-risk
patients thus identified.
As long as such studies are still lacking, general prophylactic implantation of
defibrillators in postinfarction patients is not recommended, even if they are identified
as high-risk patients.
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Implantable cardioverter defibrillator -
primary prevention of sudden death
prophylatic ICD implantation, postinfarction patients, CAST trial, class I drugs, MADIT
trial, EMIAT trial, CAMIAT trial, left ventricular function, non-sustained ventricular
tachycardia, risk stratification, mortality rate, R
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