A new study suggests that coating stents - shown here - with sildenafil may reduce the risk of blood clotting and restenosis.
Stents are tiny tubes made of metal mesh that are inserted into clogged arteries to keep them open and allow the blood to flow more easily.
According to the American Heart Association (AHA), stents are "fairly common." They are used when arteries are narrowed due to the buildup of plaque, in an attempt to reduce the chances of a heart attack.
For some patients, stents reduce the risk of "restenosis" - the renarrowing of arteries. But for others, they can have the opposite effect, as tissue growing excessively around the area treated with stents can make the arteries become narrow or clogged again. This tends to happen in the case of so-called bare metal stents, which are stents that are not coated with drugs.
By contrast, stents that are covered with drugs in order to prevent the blood vessels from closing are called "drug-eluting stents."
Sometimes, however, drug-eluting stents may also cause other complications. For instance, despite anti-clotting treatment, blood clots may still develop near the stent.
But new, preliminary research finds that coating stents with a drug normally used for treating erectile dysfunction may prevent the arteries from clogging or narrowing again.
The findings were presented at the AHA's Basic Cardiovascular Sciences 2017 Scientific Sessions in Portland, OR. The lead author of the study is Dr. Han-Mo Yang, associate professor in the division of cardiology at Seoul National University Hospital in South Korea.
Sildenafil reduces platelet clumping
Dr. Yang and colleagues carried out a series of tests in rodents, examining the effect of the drug sildenafil on blood clotting.
Sildenafil is used to treat erectile dysfunction, although the drug was originally developed as an antihypertensive medication. The drug is now sold either as "Viagra" or "Revatio" - the former for erectile dysfunction, while the latter is used to help adults with pulmonary arterial hypertension exercise more.
The drug can increase the blood flow and relax the arteries, thus allowing the blood to flow more freely.
The new research revealed that sildenafil "reduced clumping of blood platelets by 30 percent."
Platelets are part of the reason why we do not bleed excessively when we get a small cut. They are cells in our blood that can detect a damaged blood vessel and "come to the rescue" by binding together and forming a blood clot.
Of course, in the case of people prone to having clogged arteries, doctors may prescribe anti-platelet drugs to reduce the risk of a heart attack or stroke.
In the new study, Yang and team found that sildenafil increases the activity of an enzyme called the protein kinase G (PKG).
PKG prevents the walls of the arteries from thickening after an injury, so it may help avoid the complication that sometimes occurs after stent placement surgery.
As the authors explain, stent implantation lowers PKG activity, which leads to the thickening of the arteries and an increased binding of platelets. Therefore, PKG activation is crucial to the mechanism through which sildenafil can prevent restenosis.
"Our study is limited by involving only animals. If clinical trials show that sildenafil reduces restenosis after stent placement, it could be used in the clinical setting right away because the drug is already used in the real world for other purposes," says Dr. Yang.
"[S]ildenafil could be an ideal drug for coating drug-eluting stents or to give orally after stent implantation."
Dr. Han-Mo Yang