Biomedical Engineering Reference
In-Depth Information
thienopyridine therapy, and should contact the patient's cardiologist to discuss
optimal patient management.
6. Elective procedures that carry a risk of bleeding should be delayed until a month
after the patient has completed an appropriate course of thienopyridine therapy,
which is ideally 12 months after receiving a drug-eluting stent in patients who
are not at high risk of bleeding, and at least 1 month after a bare metal stent.
7. For patients who receive a drug-eluting stent and who must have procedures that
mandate stopping thienopyridine therapy, aspirin should be continued if at all
possible, and the thienopyridine restarted as soon as possible after the procedure
(due to concerns about late stent thrombosis).
8. The healthcare industry, insurers, congress, and pharmaceutical industry should
insure that issues such as drug cost do not cause patients to prematurely discon-
tinue thienopyridine therapy and incur catastrophic cardiovascular complications.
Clopidogrel Use and Long-Term Outcomes of Patients Receiving DES
Clopidogrel (sold as Plavix) can be used along with aspirin for 3-6 months follow-
ing stent placement to prevent thrombosis, but the drug is not free of risks. It can
cause thrombotic thrombocytopenic purpura, a rare disorder of the blood coagula-
tion system. Also, clinical trials have revealed that use of clopidogrel can, in rare
cases, increase risk of hemorrhage or lead to decreased levels of white blood cells,
and, more commonly, cause stomach pain, gastrointestinal disturbances, headaches,
and dizziness. Patients taking clopidogrel must stop taking the drug if they are
scheduled to undergo surgery or some other type of invasive medical procedure that
might lead to bleeding.
Recent studies of DES suggest that current antiplatelet regimens may not be
sufficient to prevent late stent thrombosis. An observational study of clopidogrel
use and long-term clinical outcomes of patients receiving DES and BMS for treat-
ment of coronary artery disease has concluded that the extended use of clopidogrel
in patients with DES may be associated with a reduced risk for death or myocardial
infarction (Eisenstein et al.
2007
). Heart patients who have received drug-coated
stents to hold open an artery and who stop taking the drug clopidogrel to reduce
blood clotting may face more than double the risk of death or heart attack than
patients who continue on the drug. However, the appropriate duration for clopi-
dogrel administration can only be determined within the context of a large-scale
randomized clinical trial.
Effect of Blood Clot on Release of Drug from DES
Although a DES delivers potent compounds directly to arterial segments, it can
become clot laden when deployed. The affect of thrombi on paclitaxel elution
and arterial uptake has been studied. Blood cells bind and retain paclitaxel such
that levels in clot increase linearly with red cell fraction. At physiological
hematocrit, clot retains three times the amount of paclitaxel in surrounding solu-
tions. Computational models predict that the potential of thrombus to absorb,
Search WWH ::
Custom Search