Biomedical Engineering Reference
In-Depth Information
In contrast to this, another study showed that compared with on-label use, off-label
use of drug-eluting stents is associated with a higher rate of adverse outcomes during
the index admission and at 1 year (Win et al.
2007
). Stent thrombosis occurred
predominantly in patients who underwent off-label drug-eluting stent implantation.
By reducing restenosis, the DES have saved tens of thousands of patients from
the risks of follow-up stenting procedures or bypass surgery. But it would take a
study involving tens of thousands of patients and as many as 5 years to produce
highly reliable data on whether those benefits offset the risks of the blood clotting
now associated with the DES. Therefore, long-term safety data are essential for
DESs. After a DES gains market approval, the FDA requires quarterly report of
details of follow-up on each stent in addition to the usual adverse event reporting.
Follow-up studies lasting at least 5 years must be performed and manufacturers
must set up a national registry to follow at least 2,000 patients for 1 year. Boston
Scientific is taking a lead in this matter by TAXUS study.
As DES implantation becomes more liberal leading to an extensive use of this
technology, the problem of restenosis in DES will become more common. However,
little is yet known about optimal treatment of in-stent restenosis following DES
implantation. Future research is needed to determine if these patients should be
treated with the same drug-eluting stent, with a different drug-eluting stent, or with
increased doses.
In one study of patients, endothelium-dependent vasomotion of a coronary seg-
ment 15 mm in length, starting 2 mm distal to the SES, was assessed with quantita-
tive coronary angiography immediately after the procedure and at 6 months
follow-up, after intracoronary infusion of acetylcholine (Hofma et al.
2005
).
Intravascular ultrasound was performed and coronary flow reserve assessed in all
patients. Results of this study indicate that SES implantation may have an adverse
effect on local endothelium-dependent vasomotor responses compared with bare
metal stent implantation at 6 months. Long-term clinical consequences of this
observation are still unknown.
A study in Canada showed that the 2-year rate of target-vessel revascularization
was significantly lower among patients who received DES than among those who
received BMS (Tu et al.
2007
). DES were associated with significant reductions in
the rate of target-vessel revascularization among patients with two or three risk fac-
tors for restenosis (i.e., presence of diabetes, small vessels, and long lesions) but not
among lower-risk patients. The 3-year mortality rate was significantly higher in the
BMS group than in the DES group. It was concluded that DES are effective in reduc-
ing the need for target-vessel revascularization in patients at highest risk for resteno-
sis, without a significantly increased rate of death or myocardial infarction.
Regulatory Issues of DES
In 2006, the FDA provided the following information in response to inquiries on
the agency's position on adverse events related to coronary DES. A summary is as
follows:
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