Heart Attack | Coronary Artery Disease | Cholesterol | Stents | Heart Bypass Surgery
Under Construction

We are talking about coronary artery stents here.

A stent is a tiny wire mesh tube. It props open an artery and is left there permanently. When a coronary artery (an artery feeding the heart muscle) is narrowed by a buildup of fatty deposits called plaque (atherosclerosis), it reduces blood flow and will cause angina (chest discomfort or heart pain) or shortness of breath after exercise.

Symptoms are usually checked out with a stress test and nuclear scan and an echo cardiogram. If a problem is indicated a coronary angiogram is usually recommended with a procedure called Cardiac Catheterization.
A thin, hollow tube called a catheter is inserted into a large blood vessel that leads to your heart.
Coronary angiography is done during cardiac catheterization. A contrast dye visible in X-rays is injected through the catheter. X-ray images show the dye as it flows through the heart arteries. This shows where arteries are blocked.
Then, a smaller balloon catheter will be fed through the flexible catheter and inflated at the narrowed area to open it and place a stent.

Stents are usually placed only if there is a 70% or more blockage.
However any blockage is an indication of progressive coronary artery disease and things such as lifestyle changes such as exercise, weight loss and dietary modification are recommended.

Mild blockage 20-40% No blood flow restriction
Moderate blockage 40-70% No significant limitation to blood flow and so does not cause symptoms.
Blockage at the higher end of the moderate range (50-70%) may require additional testing to see if it is significant or not and may be responsible for symptoms.
Severe blockaage >70% Stenting or bypass surgery is usually recommended.

Stents are used with percutaneous coronary intervention (PCI) or angioplasty. In it, a balloon-tipped tube (catheter) is inserted into an artery and moved to the point of blockage. Then the balloon is inflated.
The stent is placed over the balloon and stays in place to keep the artery open.

See video .

Although stented arteries have less chance of renarrowing than arteries opened with a balloon alone, in-stent restenosis (renarrowing) caused by tissue growth can still occur in more than 1 in 5 patients after stent placement.
This usually happens in the first 6 months after the stent is placed.

Recurrent angina may occur during the first couple of weeks following stent implantation. Often this is due to coronary spasm. When a vessel is dilated and stretched it becomes sore and inflamed much like a cut on the skin. Until this area heals the vessel may go into spasm due to it being raw and irritated.

Because stents expose foreign material to the blood stream, a small risk exists that a blood clot may develop in the stent, a process called stent thrombosis. These blood clots can occur many months and even years after stent implantation and may lead to a heart attack.
However, the risk of blood clots is greatest during the first few months after the stent is placed.
For this reason, most patients with stents are instructed to take blood thinners, usually in combination with aspirin

A Duke University study found that there was a 1 in 40 chance of forming a blood clot in a drug-eluting stent when people were on blood-thinning medicine, but a 1 in 20 chance for people who stopped taking blood-thinning medicine after six months.

Over time (about a year), cells like those on your artery wall will grow over the stent and many time the blood thinners can be discontinued then.

Blood Thinners
There are two main types of blood thinners. Anticoagulants, such as heparin or warfarin (also called Coumadin), work on chemical reactions in your body to lengthen the time it takes to form a blood clot. Antiplatelet drugs, such as aspirin, prevent blood cells called platelets from clumping together to form a clot.

A 1999 study by the NIH was primarily to show that new antiplatelet drug Ticlopidine (trade name Ticlid) produced better outcomes.
Survival at one, three, and five years was 95%, 91%, and 86%, respectively.
Source: Long term outcome after coronary stent implantation: a 10 year single centre experience of 1000 patients - NIH 1999


Bypass surgery, Coronary artery bypass graft surgery (CABG), became common in the 70's to treat atherosclerosis
In the 80's atherosclerosis in a couple of arteries was treated by angioplasty (a balloon to push the plaque back) alone.
By 1996 over half of the procedures included a stent placement.
Drug-eluting stents came into favor in the early 2000's
And the Absorbable Heart Stent in 2016.
See: History of Angioplasty Timeline

Drug-eluting stents (DES):
Sometimes there is excessive growth of tissue (scar tissue) at the edge of the stent causing restenosis.
In early 2000 stents (called drug-eluting stents) that have medication on them to inhibit or prevent excessive tissue growth were introduced.

Concerns about the safety of drug-eluting stents have received much publicity, primarily related to a small increase in the number of blood clots that develop within drug-eluting stents late (more than 1 year) after implantation. In December 2006, the US Food and Drug Administration convened a panel of cardiovascular experts to review drug-eluting stent safety data. The panel concluded that for many patients, such as those with uncomplicated medical histories who undergo elective stenting of simple coronary blockages, drug-eluting stents remain a safe and appropriate therapy. For others, such as those who have suffered an acute heart attack or those with multiple or complicated coronary blockages, current data are inadequate to determine whether drug-eluting stents are better or worse than bare-metal stents or coronary artery bypass surgery.

Older patients treated with drug-eluting stents had a 54 percent lower need for repeat treatments than those treated with bare-metal stents.
See: Drug-Eluting Stents I

Absorbable Heart Stent:
In July, 2016 the U.S. Food and Drug Administration approved Abbott Laboratories' absorbable heart stent called Absorb.

The current state of the art are drug-coated stents. The drug gradually seeps into the interior of the blood vessel to prevent growth of scar tissue that can cause clots to form.

But recent research shows that the drug-coated stents are associated with serious adverse events, including death and heart attack, at a rate of 2% to 3% a year. The hope is that a dissolvable stent will reduce such problems.

A 2008-person study, called Absorb III, found that 7.8 % of patients treated with the new device suffered "a major cardiac adverse event," a rate that was "clinically comparable" to the 6.1% rate for those treated with Abbott's drug-coated metal stent called Xience.

because Absorb leaves nothing behind it may provide significant long-term benefits, such as a restored vessel in a natural state and renewed possibilities for people treated with Absorb," said Dr. Charles Simonton, chief medical officer of Abbott Vascular in a statement.
- Coronary Angioplasty/Stenting - Heart Center Of North Texas

Google Search
What Is a Stent? - American Heart Association
Drug-Eluting Stents | Circulation - AHA Journals
FDA Approves Abbott's Absorbable Heart Stent - WSJ
Abbott's bioresorbable stent meets primary endpoint, but NEJM editorial raises questions | FierceBiotech
What Are the Risks of Having a Stent? - NHLBI, NIH

Coronary Stent

last updated 7 July 2016