Brussels, 21 Sep 2006
A Eureka project involving Irish and Dutch researchers has developed a device designed to help keep narrow or blocked arteries open for longer, thereby ensuring a steady flow of blood to the heart and reducing the number of deaths due to blocked arteries. Blood is supplied to the heart through the coronary artery, a blood vessel which is unfortunately prone to narrowing. When this happens, blood flow to the heart is restricted, leading to serious conditions such as angina or heart attack.
For many years, doctors have been able to insert supportive structures called stents into narrowed arteries. This is done by inserting the collapsed stent into the artery with a balloon catheter inside it. Once the stent is in position, the balloon is inflated and the stent expands until it is supporting the artery and holding it open.
Over the years the procedure has become extremely popular. In 2005, 2.5 million procedures were performed around the world and the international market for stents and balloon catheters is valued at around €1.9 billion.
However, the procedure often causes damage to the walls of the artery, and scar tissue can form around the stent, effectively re-blocking the artery. To prevent this problem, stent manufacturers began to coat the stents with a biodegradable polymer bound to a drug to control this excess cell growth.
Yet these so-called 'drug eluting stents' are still far from perfect. '85 per cent of the drug, which is very toxic, remains in the coronary vessel for the rest of the patient's life because it is bound in the polymer and is not eluted,' explains Ronald Horvers of Blue Medical Devices in the Netherlands. 'The other problem is that because the drug is so toxic, it kills the cells around the stent, raising a danger of thrombus (blood clotting within the vessel).'
To get around this problem, Blue Medical Devices set about developing a bio-absorbable polymer stent coating which would be completely absorbed in around three weeks, as well as two drugs to prevent excessive cell growth at relatively low toxicity levels.
Applying an even coating of the polymer to the stent is extremely difficult; the mesh wire is just 0.1 mm thick and the device itself is a mere 14 mm long and 1 mm wide. Irish company Craganna Medical Devices has considerable expertise in coating metal parts, and they successfully developed a system which applies a uniform layer of polymer to the stent.
Once the stent is in place in the artery, the drugs are released into the surrounding area, where they restrict the development of excessive smooth muscle cells on the artery wall. By the time the biopolymer has broken down, the full dose of the drug has been released, leaving none behind on the stent.
Human trials of the product started earlier this year, and early indications are that cardiac surgeons will be keen to use the new device.
According to Mr Horvers, the benefits of being involved in the Eureka initiative went beyond the financial aspects. 'Being a Eureka-approved project unquestionably raised the status of the project,' he commented, adding that it had also enabled strong international working relationships to be developed.
Heart disease and blocked arteries are major killers in the western world; according to figures from the World Heart Federation, cardiovascular disease kills 17.5 million people around the world every year, and causes just under half of all deaths in Europe.