Biomedical Engineering Reference
In-Depth Information
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FDA has been monitoring coronary DES closely since they came on the US
market in 2003 and 2004, and will continue to do so.
New data were released recently that suggest a small but significant increased
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risk of stent thrombosis in patients who have DES. The agency is keenly inter-
ested in this issue because of the potential for serious harm to patients − even
though stent thrombosis occurs at low rates.
While the new data are of interest to FDA and raise important questions, it does
•
not have enough information yet to draw conclusions. It is unclear, for example,
what causes DES thrombosis, how often it occurs, under what circumstances it
occurs, or what the risk of occurrence is in a given patient.
To better understand this issue, FDA met with the two manufacturers of these
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products in recent months to discuss any information they might have pertaining
to this issue and get their perspective. In addition, it plans to convene a public
panel meeting of outside scientific experts in the near future to assist us in a
thorough review of all the data and make recommendations about what actions
may be appropriate, such as possible labeling changes or additional studies.
At this time, FDA believes that coronary drug-eluting stents remain safe and
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effective when used for the FDA-approved indications. These devices have sig-
nificantly reduced the need for a second surgery to treat restenosis for thousands
of patients each year.
There are reports of subacute thrombosis associated with the stents and associ-
ated patient deaths. Taxus Express was associated with failure of the stent delivery
balloon to deflate after the stent was inserted; these were associated with serious
injuries and death. Boston Scientific traced the problem to a manufacturing error
and corrected it. Although the adverse events are rare, risks have to be balanced
against benefits in DES. Obviously, such challenges will continue to occur with
breakthrough technologies and devices. The FDA perspective at that time was sum-
marized in a publication (Muni and Gross
2004
). DES have been evaluated in
patients previously only considered for surgical intervention. Assessment of DES
in these complicated patient populations can lead to challenges in trial design, but
the FDA has considered alternative clinical trial designs and statistical analysis
plans (Boam
2006
). Other complex issues associated with DES include duration of
clinical trials to determine safety, and the appropriate dose and duration of con-
comitant antiplatelet therapy.
In the light of the published studies suggesting that DES may pose a risk of throm-
bosis that was not observed during premarket testing, the FDA convened a meeting
of its Circulatory System Devices Advisory Panel in 2006 to examine the safety of
these devices. The FDA will carefully consider the information and views presented
at the meeting in deciding on future actions. The panel agreed, and the FDA concurs,
that when DES are used for their approved indications, the risk of thrombosis does
not outweigh their advantages over BMS in reducing the rate of repeated revascular-
ization (Farb and Boam
2007
). But the panel also concluded that, as compared with
on-label use, off-label use is associated with increased risks of both early and late
stent thrombosis, as well as death or myocardial infarction. The panel concluded that
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