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© 2011, 2012 Health Futures Digest
| Stents that open clogged arteries are amazing technology and have doubtless saved many lives, not to mention brought vascular surgeons, cardiac surgeons, and interventional cardiologists almost to fisticuffs. But today’s stents are not perfect, and there is much effort under way to improve them . . . and even to replace them with tissue-engineered vascular grafts: “New blood vessels for old!” could soon be the marketing slogan of choice for vascular interventionalists. A tissue-engineered vein transplanted into a dialysis patient was holding up well after six months.
Other interesting device news — medical and other:
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| Next in Stents
Drug-eluting stents, writes Stephen Heuser in the Boston Globe, leave much room for improvement. They can be difficult to thread through bends and constrictions in arteries, hard to install in the vessels’ tight turns, cause allergic reactions, and have even (though rarely) led to patient death during the implant procedure. Another problem is that the polymer used to attach drugs to drug-eluting stents does not dissolve completely. Much of it, and of the drug attached to it, remains permanently within the patient. Various efforts are underway to overcome these issues. Biosensors International is awaiting European approval of a stent with a polymer coating that would dissolve completely. Conor Medsystems is conducting trials of its CoStar stent, which uses a dissolving polymer and a stent designed to store the drug in tiny holes in its metal struts, to reduce the amount of polymer required. At least two other companies, reports Heuser, are developing a new type of drug that sticks directly to the metal stent without need for a polymer intermediary. Guidant Corp. and Boston Scientific have research programs to develop dissolving stents. Biotronik has already begun human tests in Europe of a magnesium stent that completely dissolves in two to three months, after the artery it was designed to support has healed. The next version of Boston Scientific’s market-leading Taxus stent, called the Liberté, has a mesh structure that makes it more flexible and has been approved in Europe. It also is considering a platinum alloy designed to be well tolerated by the body. The company also has an experimental stent made of niobium which is undergoing clinical trials in Europe. Startup firm Electroformed Stents has developed a gold stent to treat brain aneurysms, though has had no takers so far. The use of gold, platinum, niobium, magnesium, and other exotic metals such is not likely to have much effect on the cost of stents, since they are very small and the price is already very high (nearly US$3,000 list price). The implant into humans last year of the first blood vessels tissue-engineered in a laboratory could benefit a large number of patients, said the director of the US National Heart, Lung and Blood Institute, which provided more than US$2.5 million into the development of the vessels. Those patients would include diabetics who must undergo routine kidney dialysis, children born with defective blood vessels, and heart bypass surgery patients. The vessels were engineered from small pieces of skin and vein taken from the back of the hand and grown in the laboratory to produce two types of tissue: one “a tough, structural material that gives the vessel its shape,” and the other “a softer material that serves as the lining and prevents blood clots,” according to an article in the Detroit News. Sheets of the two tissues are then stacked and rolled into vessels about 6 to 8 inches long. “The process takes six to nine months and costs about $10,000, but Cytograft Tissue Engineering, the company that makes the vessels, hopes to make it faster and cheaper,” says the paper. The vessels have been implanted in a 56-year-old woman and a 61-year-old man in Argentina, both diabetics who were running out of healthy vessels to connect to the dialysis machine. The woman’s vessel has so far been punctured three times a week for dialysis for six months without damage, the man’s for three months. Tests on groups of 25 patients each are planned for Argentina and the UK. Source: Advisory Board Daily Briefing (subscription service), October 18. The Heartsbreath test is a “breathalyzer” for heart transplantees. The patient breathes into a tube for two minutes, and the collected breath sample is chemically analyzed using gas chromatography and mass spectroscopy techniques. If the test indicates that the new heart is not being rejected the patient would be able to avoid one or two of the biopsies that are typically performed more than a dozen times within the first year of a patient receiving a heart transplant, making life better for the patient and reducing costs for the payer, since the breath test will likely cost only a “few hundred” dollars, compared with thousands of dollars for the typical heart biopsy. However, the test is less sensitive and less specific than a biopsy and has been approved only as an “adjunct to a biopsy but not a replacement.” The device is now being evaluated to diagnose early stage lung cancer, and NIH-sponsored clinical trials are underway to test for tuberculosis. Given:
it is no surprise that a leading manufacturer of cochlear implants estimates market growth at 15 to 20 percent a year. Since their introduction in 1984, the devices have evolved from analog to digital and from single electrode to multiple electrodes with improved speech-processing, writes Ranit Mishori in the Washington Post . In one case described in detail by Mishori, the total cost of the implant, including evaluation, surgery, the device and post-operative rehab was around US$40,000. Insurance covered this patient’s surgery and follow-up care, though not the required pre-surgical psychological evaluation. University of Nebraska researchers have developed prototype surgical robots about the size of a 3-inch lipstick case to help doctors on Earth perform surgery on astronauts in space. The devices can be inserted into the body through small incisions and controlled by surgeons on Earth. Two different robots would be inserted. One would have cameras and lights to send back color images that can be magnified, giving the surgeon a better view than s/he sees in open surgery; the other would have the surgical tools and be more maneuverable than the human hand working in open surgery. Their developers think the devices could replace open surgery not only in space but also on Earth. On battlefields, for example, remote surgeons could operate on injured soldiers on the front line. Tests on animals have been successful, and tests on humans will begin in England in the Spring of 2006. A robot capable of doing biopsies is in the works and another is being designed that can be inserted into a person’s stomach via the esophagus. The robots themselves currently cost about US$200 each, Australia’s premier research institution, CSIRO, has developed collars for free-range cattle that can “trace animals from paddock to plate.” The collars are comprised of: GPS unit, inertial sensor, digital compass, transceiver, and computer They enable the farmer to track “Social interactions, calf-cow relationships, herd movement and even carrying capacity of the environment,” a CSIRO executive said. Such information will help to improve food safety, disease prevention, improved breeding programs, “and even market access.” CSIRO is also investigating the possibility of using the collars to control animal behavior remotely by incorporating buzzers or vibrators and an electric shocker. Israel Produces Fuel Cell Solution An Israeli company hopes to build on groundbreaking work conducted at the Weizmann Institute to develop a system to produce hydrogen inside a car from water, plus common metals such as magnesium and aluminum. The system would overcome the barriers associated with the manufacturing, transporting, and storing of hydrogen for use in fuel-cell driven engines. A magnesium or aluminum coil would be partially immersed in a “metal-steam combustor” (effectively, the gas tank). The coil would be heated to very high temperatures, causing its metal atoms to bond with oxygen atoms in the water, creating metal oxide and freeing the water’s hydrogen atoms. Refueling would be necessary when the metal coil is used up, and would involve suctioning out the metal oxide waste (which would then be sent for recycling) and inserting a new roll of wire. The wire would weigh about 100kg (220 pounds) to produce mileage equivalent to today’s cars. The company is looking for funding to develop a prototype in about three years. |
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