Artificial veins get to the heart of surgery

HEART bypass operations will become much easier to perform, and the results last longer, with the development of an artificial blood vessel that surgeons will be able to order 'off-the-shelf'.

An American company, Organogenesis, is working on the world's first man-made vein, designed to allow previously inoperable patients to receive life-saving heart surgery.

At present, the veins used to replace damaged blood vessels in the heart are taken from elsewhere in the patient's body, but around a third of those eligible for such surgery cannot have it because their other veins are also affected by disease.

The new graft, currently undergoing animal trials in the US, will also spare bypass patients the discomfort of vein retrieval.

"It would be a tremendous advance," said surgeon Pankaj Mankad of Lothian University Hospitals Trust. "At present there are significant side-effects associated with taking veins from the legs: there may be a huge scar which can become infected; discomfort may mean it is difficult to walk; the vein is not so good under high-pressure, and roughly 50% will block within ten years. We really need a fool-proof long-term replacement, and this approach may well be it."

The artificial graft, which is 20 times stronger than a human vein, acts as a biodegradable scaffold, allowing the patient's own tissue to re-grow and replace it.

"Early data shows that the host's own cells grow into the graft, creating what we call a neo-vessel," said Organogenics spokeswoman, Laurie Doyle. "We think that over time, the graft may be replaced entirely with the patient's own vein."

Research trials have shown that the artificial vein, once it is converted into living tissue, also constricts and dilates in response to natural stimuli. "We are cautious about making too many claims until all the trials are complete," said Doyle. "But, yes, this is really exciting work with enormous human potential."

The artificial vein is constructed using collagen, a protein that is the principal constituent of connective tissue, in this case harvested from the intestines of pigs and cows.

"Animal collagen has never been used in this way before," said Doyle. "It does seem to have advantages in that humans are not likely to reject it."

After special cleaning removes any vestiges of animal cells, the collagen is turned into a double-layered 4mm-diameter tube which is coated with an anti-coagulant to prevent clotting of the blood that will pass through it.

"It looks like a thin straw," said Doyle. "We want to mass- produce a product that doctors planning heart bypass procedures can order and use right away. It will be a few years before it is on the market as we have to be sure what will happen to the grafts over time."

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