Coronary artery disease (CAD) is one of the biggest killers in the world today and most common cause of heart attacks. It’s caused by plaque build-up along the inner walls of the arteries and it can be caused due to numerous reasons. The most common ones are lifestyle habits like an unhealthy diet, lack of exercise, alcohol consumption and smoking. The more urgent cases require an angioplasty or bypass surgery.
The treatment of CAD depends on many factors – patient’s age, heart function and overall health. Often it can be something as simple as focussing on lifestyle changes like quitting smoking, eating a heart healthy diet and engaging in physical activity. Medical management includes prescribing aspirin, medicines to reduce the workload of the heart or medicines to reduce high blood cholesterol levels or high blood pressure are also given. If none of these treatments prove effective, a patient has to undergo either of the two procedures – a balloon angioplasty or a bypass surgery. While a bypass surgery involves grafting arteries or veins from other parts of the body area to the coronary arteries, a balloon angioplasty involves threading a tube into the artery which will expand and allow more blood flow. Dr Vijay Surase, an interventional cardiologist at Jupiter Hospital, Mumbai tells us about the latest in angioplasty – biodegradable stents!
Balloon angioplasty stenting is a procedure which involves threading a thin tube into the artery and then expanding the balloon-like apparatus as a way to increase the size of the artery to increase blood flow. The first angioplasty was performed in 1977 and the only drawback was the effect of the stents left behind in the patient’s arteries. Being a foreign object, the stent could cause an adverse response from the immune system. This can lead to problems like scar tissue over the stent and also clot formation. Since the early days, cardiologists have been dreaming of a scaffold that would disappear after the job was done. They finally saw that materialise in 2012 with the advent of biodegradable stents.
But to understand the how marvellous biodegradable stents are, we need to understand what stents are. Basically, they are slotted metal tubes effectively appearing like a spring of a ball pen refill but with very fine steel metal or other metal alloy threads knitted to each other. They are usually of two types – Bare Metal Stents and Drug Eluting Stents.
The drug eluting stent is the more advanced and effective of the two and work by releasing a drug to block cell proliferation. The newest generation of drug eluting stents are the bio-absorbable stents also known as the bio-resorbable vascular scaffold system (BVSS).
The bioabsorable stents are usually made of four components:
- Bioabsorbable scaffold
- Bioabsrobable coating
- Drug – Everolimus (an immunosuppressant to prevent rejection)
- Delivery System
Why are biodegradable stents better?
The stents are made of polylactic acid, a proven biocompatible material that is usually used in medical implants. As with a metallic stent, bio-absorbable stent is designed to restore blood flow by propping a clogged vessel open, and to provide support until the blood vessel heals. Unlike a metallic stent, however, a bio-absorbable device is designed to be slowly metabolized by the body and completely absorbed over time. This results in a zero percent rate of stent thrombosis (blood clot formation) for all patients over the next two years.
Benefits of biodegradable stents (though technically they aren’t stents and a better term would be scaffold):
- Vessel scaffolding is only needed for a while
- It leaves no residual scaffold behind
- They restore the vessel to a natural state, which makes it capable of natural vascular function
- There is no vessel irritation and inflammation
- Vessels remain free for further treatment (a metal stent would just be there and make that vessel unusable) and it can be used for further stenting or in case a bypass surgery is needed
In totality, it’s one of the greatest medical inventions in recent history because of its ability to vanish after its work is done. It’s like ice that melts and becomes water. The only by-products left in this cases are water and carbon dioxide. The water is used by local tissues and carbon dioxide is used for energy production at cellular levels. Despite being expensive, there’s reason to believe that biodegradable stents will become the norm in the future.