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The Role Played by Drug-Eluting Stents in Reducing Mortality in AMI

The safety debate about drug-eluting stents (DES) is still ongoing. In these times of uncertainty about DES safety, the study has shown that DES markedly improve long-term survival compared to modern bare-metal stents (BMS) implantation in patients with acute ST-segment elevation myocardial infarction (STEMI). In our four year investigation, DES demonstrated a significant reduction of mortality in this sick patient subset.

The study sought to present a subgroup analysis of patients with myocardial infarction followed long-term for a mean of four years in the FReIburger STent Registry (FRIST), a single-centre registry in high volume tertiary referral cardiovascular centre. FRIST included complex coronary patients treated with DES and BMS in the University Hospital of Freiburg, Germany, according to non-selected inclusion criteria. For the first time, three drug eluting stents, namely Cypher®, Taxus® and Endeavor®, were compared. The DES-groups were matched to a historical, contemporary BMS control group.

The primary study endpoint was overall survival. Cardiac and non-cardiac death was also analysed. We observed a significant survival benefit of patients who received DES compared with patients who received BMS in FRIST. The overall crude incidence for all-cause death was 7% (13/186) in the DES-group and 24% (27/112) in the BMS-group. Applying a multivariate Cox survival model with adjustment for existing baseline differences between the patient groups resulted in a relative risk of 0.42. That implies a 58% decrease of mortality risk in the DES population within the four year observation period. The adjusted risk reduction with respect to cardiac death (-70%) was even more impressive.  A number needed to treat analysis (NNT) looking at mortality indicated that if 30 patients were treated with a DES instead of a BMS in STEMI, one life could be saved.

The analysis clearly favours DES implantation with a marked long term survival benefit in patients with myocardial infarction over BMS. Reduced total mortality for DES as compared to BMS, and a further reduction with respect to cardiac death suggests, that many patients can profit from “off-label” use of DES. This registry shows for the first time that DES are not only equal but clearly superior to BMS when long-term survival is the primary concern in patients with STEMI. The data supports the TYPHOON-results but should be interpreted with caution until further randomized mortality trials have substantiated the reported findings.

DES were designed to reduce the likelihood of vessel narrowing (restenosis) after catheter treatment, and they are very effective at doing just that. So, cardiologists quickly embraced the new technology and DES were applied in a variety of clinic scenarios previously not looked at in the pivotal randomized trials. 

The so called “off-label” use of DES quickly emerged. Not surprisingly, unanticipated adverse events were reported several years after introduction of DES into the market. One of the most important issues is stent thrombosis, a potentially life-threatening complication which can result in abrupt vessel closure and subsequently myocardial infarction and/or cardiac death. 

Unfortunately, clinicians are confronted every day with complex heart disease and risk factors that do not conform to the controlled environment of randomized trials. In order to obtain more information about the outcome of DES in “off label” use, registry inquiries have recently taken on increasing importance worldwide. Registry studies are able to show how far the results of randomized trials are transferable into daily routine, and can shed some light on safety aspects of treatments.

Myocardial infarction (MI) is a hotly debated “off-label” use of DES. Primary coronary angioplasty with stent implantation is now considered the standard of care. However, knowing increased coagulatory and inflammatory responses typical in MI, the use of DES in MI has been found to be very controversial. Thus a potential safety issue of DES in MI patients was raised, but information on long-term outcomes of different stents in the real world doesn’t exist at the moment.