Overview of Intracoronary Stents
In 1977, Andreas Grunzig in Zurich, Germany conducted the first ever balloon angioplasty, a procedure to open a blocked heart artery, on Andreas Bachman. This procedure was a success and Bachman’s artery stayed open for another 10 to 20 years. But unfortunately, this procedure isn’t always as successful. In fact, for 5% to 10% of patients, the artery closes again soon after the procedure. This follows a reaction where the balloon causes damage at the edges of the artery blockages, which can then lead to blood clotting and the artery re-closing.
This led to the development of bare metal coronary stents, which are like little scaffolds inserted into the artery to hold it open. Initially, these stents were made from thick stainless steel and weren’t very flexible. But, these stents helped with the issue of arteries re-closing immediately after balloon angioplasty. However, they introduced a new problem: these stents themselves caused the formation of blood clots, a condition known as stent thrombosis. This issue was managed with a combination of drugs that prevent clotting.
Though these stents helped manage the problem, there was another issue: these stents could lead to a condition called in-stent stenosis, where the artery re-narrows at the stent site. This happens due to the body’s reaction to the stent, causing excess tissue to grow, closing up the artery again. It was found that the bare metal stents had a high risk of re-narrowing between 20% to 50%.
To combat this, drug-eluting stents were developed. These stents slowly release medicines to prevent excessive tissue growth. These first-generation stents were made of stainless steel and were quite thick, which made them difficult to use in severe cases. Despite their shortfalls, they reduced the need for re-treatment of the artery by 50% over 5 years compared to plain metal stents.
Their main problem was that in rare cases they caused late stent thrombosis, potentially leading to a heart attack. It was found that around 60% of stented areas never fully healed, probably due to the strong combined effect of the drug and polymer used in the stent.
To resolve this, second-generation, drug-eluting stents were developed. These thinner stents heal faster and create less inflammation in the artery. They are more flexible, and slightly change the drugs used that are less likely to interfere with healing. These stents performed much better, reducing the chances of serious heart issues and reducing late stent thrombosis by about 70% within 24 months.
The ongoing development is towards third-generation stents. These are designed to be even thinner and use materials that gradually dissolve over time, or none at all. Trials with these newer stents have shown promising results, with lower rates of heart issues and even better performance.
In the future, we might see stents without any polymer at all, instead holding the medicine directly in the metal structure. These could potentially allow for shorter treatment times with antiplatelet drugs and may avoid some of the issues associated with the polymers. In trials, such a stent performed better than a simple metal stent in reducing the chances of the artery narrowing again, heart attacks, and death. However, the risk of stent thrombosis was similar.
Anatomy and Physiology of Intracoronary Stents
When placing a stent (a small mesh tube) in a blood vessel of the heart, the shape and size of the blood vessel are very important. The stent is chosen to match the maximum size of the part of the blood vessel where it will stay. If the blood vessel seems to have a good deal of hardening from calcium deposits, it might be necessary to use special imaging techniques (like ultrasound or optical coherence tomography). Doing this allows doctors to get a better look at the shape and composition of the thickened areas inside the blood vessel and determine if further treatments (like cutting or shaving away the plaque, also known as atherectomy) would be needed. Another thing doctors have to consider when placing a stent is whether it will interfere with the branching of the blood vessels and cause the plaque to shift during the procedure.
Why do People Need Intracoronary Stents
If you have a significant blockage in your heart’s blood vessels or if you’ve recently had a heart attack, your doctor might need to insert a small wire tube called an “intracoronary stent”. This is done after a procedure called a “balloon angioplasty”, which uses a small balloon to open up a blocked blood vessel in your heart. When you have a balloon angioplasty, it can sometimes damage the inside lining of your blood vessel, including the section that’s been blocked with a buildup of fats and other substances (called plaque). This damage can lead to a blood clot forming inside the blood vessel.
If you only have the balloon angioplasty without the stent placement, there is a nearly 50% chance that your blood vessel will become narrow or blocked again. When compared to using just the balloon angioplasty, using a stent – whether a bare-metal one or one coated with medication (drug-eluting stent) – results in a significantly lower chance of failing blood vessel and need for additional procedures in the future.
When a Person Should Avoid Intracoronary Stents
There are certain situations where placing a stent in a patient’s heart artery may not be suitable. These situations are mostly due to health conditions that put the patient at high risk when receiving the required medications during or after the stent is in place. Some people may not be able to take medicines that prevent blood clots, which are essential when a stent is placed.
Other conditions that may stop someone from having a stent placed include:
- Severe anemia, where there’s a lack of healthy red blood cells that carry oxygen around the body
- Thrombocytopenia, a condition where a person has very low platelets, the blood cells that help with clotting.
In addition, if a person has a severe infection in their blood (sepsis with active bacteremia) or major kidney problems, these can also make the stent placement too risky. Some other serious health conditions might also make the risks of the procedure greater than the likely benefits.
Equipment used for Intracoronary Stents
When doctors are preparing to implant a slender supporting device, called an intracoronary stent, into your artery, they need to use a genuinely specific process. They start by using a sizeable tube known as a guiding catheter, which is at least 6F or larger, to connect into the opening of your coronary artery, the coronary ostia.
Next, to avoid any unwanted blood clots during the process, the doctor will administer temporary clot-blocking medication. This can include drugs like heparin, enoxaparin, or bivalirudin. This medication ensures that the blood takes a longer time to clot – in this case, more than 250 seconds.
The procedure continues with the use of a slim, flexible guide wire, also known as a coronary wire. This wire acts as a guiding rail for the doctor. It helps guide and direct the right placement of tools such as balloons and stents (the supportive devices for the walls of your artery).
Once the wire is placed correctly, the doctor further inserts the stent on a tiny balloon. This balloon, attached to the stent, is then precisely positioned at the target site inside your blood vessel. Finally, the doctor inflates this balloon to make room for the stent using a manually-controlled device. This action is usually done by either a skilled technician or the primary surgeon themselves.
Who is needed to perform Intracoronary Stents?
When a heart doctor called an interventional cardiologist is putting a tiny tube (known as an intracoronary stent) into your heart, they’re not alone – they have a team with them. There’s a technical specialist who helps with all the equipment required, and a nurse who moves around the room ensuring that any medication, which is put into your veins (known as Intravenous or IV medication), is given when needed. This team works together to make sure that everything runs smoothly.
Preparing for Intracoronary Stents
Before a small tube called a stent is placed in a blood vessel in the heart, the vessel needs to be ready. We use a procedure called balloon angioplasty to do this. It involves using a small balloon to open up the vessel. This helps us see if the part of the blood vessel that’s blocked can be opened up, and it helps us measure the length of the blockage. But if the blood vessel has lots of hardened plaque, known as calcification, it might be harder to get the stent to the right place. In these cases, we might need to use a special tool to reshape the blood vessel and make it easier to put the stent in.
How is Intracoronary Stents performed
An intracoronary stent is a tool used to open narrowed or blocked blood vessels that supply blood to the heart. Here’s how it works:
First, the stent is carefully moved over a special wire directly into the blocked section of the artery. This is watched on a special kind of x-ray called fluoroscopic guidance, which makes it easier to make sure the stent is placed exactly where it should be. The goal is to put the stent in a place where it’s surrounded by healthy parts of the artery, both above and below the blockage.
To make this easier, the doctor might use other imaging technology, like an intravascular ultrasound or optical coherence tomography. These tools can give a better understanding of the size and shape of the blockage in the artery.
Once the stent is where it should be, the doctor then connects it to a special device that can inflate the stent to open the blocked artery. This is done with high pressure, and is watched on the fluoroscopic x-ray to make sure it’s working correctly.
After the stent is opened, the doctor may do more imaging tests to make sure that the stent is fully expanded and that there are no issues with the edge of the stent. This way, they can be sure that the stent is doing its job to help blood flow more smoothly through the artery.
Possible Complications of Intracoronary Stents
Just like when we inflate a balloon to open a blocked blood vessel (balloon angioplasty), the procedure to place a small mesh tube (intracoronary stent) inside the blood vessel can also cause complications. The blood vessel can tear or even rupture, or the stent might block the blood flow right after the procedure. There is also a chance for the stent to slip off its delivery device or balloon. Should this happen, doctors have two options. Either they can inflate where it is currently located or retrieve it using a special tool called a snare.
What Else Should I Know About Intracoronary Stents?
Despite advancements in heart stent technology, there are still areas that need improvement. Stents are small tubes that doctors use to help keep the heart’s blood vessels open. Some stents have drugs on them to help keep the blood vessels from becoming blocked again, but these can sometimes cause inflammation or allergic reactions because of the materials used to carry the drugs.
Another issue is that the material carrying the drugs can sometimes be uneven, leading to inconsistent release of the drugs. This can even create a spot where a blood clot might form within the stent.
Also, the stent can sometimes break or change shape, particularly in the right side of the heart’s blood vessels. This affects about 2% to 5% of stents.
In addition, these permanent metallic implants can straighten the heart’s blood vessels over time. This means the blood vessels lose their flexing motion and the heart has to adjust to these changes, potentially leading to more issues.
Another problem that can happen is the development of new blockages in the blood vessels, even with these second-generation stents. These new blockages can look very much like the natural ones and start forming in the layer of tissue that grows after stent placement.
In conclusion, while bear in mind these problems, companies are moving forward hoping to increase the effectiveness of the next-generation heart stents.
