Heart patients opting for metal stents over plastic

Heart patients opting for metal stents over plastic
Amaranth Medical's bioresorbable scaffold is an implant used like a stent to open blocked blood vessels. It is made of a material that can be absorbed by the body over a period of time, resulting in fewer complications for heart patients.

Metal stents are the top choice for heart patients with blocked arteries, but newer plastic scaffolds have become available that unclog blood vessels and then dissolve.

Since they became commercially available in 2012, more than 100,000 drug-eluting biodegradable plastic scaffolds have been used worldwide. They have also been used here since then.

The biggest plus point is that these plastic scaffolds disappear after a couple of years, unlike the metal stents, which will be permanently in the body.

Heart specialists still grappling with tried-and-tested metal versus new plastic attended a debate last weekend to hear the pros and cons of both.

From Germany, Dr Christopher Naber represented manufacturer Abbott to support the plastic scaffolds, while Associate Professor Tan Huay Cheem, director of the National University Heart Centre Singapore, acknowledged plastic's pluses, but urged caution in switching from metal.

Dr Naber told The Sunday Times that someone who breaks an arm and has it in a cast would remove the cast once the arm is healed. Similarly, he said, there is no reason to leave a metal stent in the artery once the blockage has been removed.

He sees absorbable scaffolds as "the logical evolution" of metal stents. He said they are as safe and effective as metal drug-eluting stents, with the added chance of restoring normal function to the arteries after two years.

Prof Tan told The Sunday Times that plastic scaffolds do have their advantages and have been used by about 15 per cent of his centre's patients with blocked arteries needing stents.

They promote good healing of blood vessels. After they have dissolved in about two years, the arteries they were holding open resume their normal function of expanding and constricting, which improves blood flow.

There are also fewer fatty deposits and the blood vessel's inner circumference can enlarge over time and is less likely to get blocked again.

And as they dissolve over time, the plastic scaffolds will not be an obstacle if the person needs another stent or a bypass operation later.

The downside, however, is that the plastic scaffold costs about $500 more than the metal stent, which costs just over $2,000. The number of stents a patient needs depends on the number of blockages and it is not unusual for heart patients to have two or three stents.

Private patients generally pay more than $20,000, while subsidised patients usually pay under $5,000 for the whole procedure.

Prof Tan's bottom line is that plastic has not been proven to result in a better clinical outcome for patients.

For it to replace metal, he feels there needs to be evidence that patients with plastic scaffolds do better - for example, with lower rates of heart attack after surgery.

He also noted that plastic is not suitable for everyone. Because it is not as strong as metal, the scaffold has to be thicker and that makes it more difficult, sometimes even impossible, to move to the affected area.

Stents and scaffolds are first inserted from an easily accessible spot, usually the wrist, and moved through the blood vessel to the spot where the blockage occurs in the heart. Plastic scaffolds are less manoeuvrable once they reach the tiny arteries in the heart.

The plastic scaffolds also do not come in as wide a range of sizes as metal stents, so they cannot be used by people whose arteries are too big or too small.

Prof Tan said his centre uses plastic generally on patients younger than 50 as they might have another blockage at another spot in future. Having a metal stent could make future treatment more difficult, whereas the plastic would have dissolved.

"It is an exciting breakthrough technology that has the potential to be the 'perfect stent' that we are looking for: a stent that 'disappears' after fulfilling its role without any long-term safety concerns," he said. But he cautioned: "The current unbridled enthusiasm with this technology has to be met with caution and judicious application."

Dr Aaron Wong, a senior consultant at the National Heart Centre Singapore said the metal drug-eluting stents remain the mainstays because the plastic scaffolds are "much more bulky" .

The plastic also cannot be seen on X-rays, he said, and this might affect delivery of the scaffold to the exact location. Unlike metal stents, plastic is also "less forgiving and cannot be expanded" without damaging the scaffold, so it is important to use the correct size for the blood vessel.

Dr Paul Chiam, a cardiologist at Mount Elizabeth Hospital, agreed that metal stents are "still the choice as they are very flexible and are much easier to deliver to the diseased artery".

Metal has also been used in millions of patients and has been proven to be very safe, he added.

He was optimistic, however, that as technology improves, the plastic scaffolds could become "less bulky and more deliverable" and will then be used more often.



This article was first published on April 26, 2015.
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