WASHINGTON (Reuters) – A Covidien Plc device for rare malformed blood vessels can get stuck in the brain and has been linked to nine patient deaths, U.S. regulators warned. The device, made by Covidien unit ev3, uses a spongy material to block off blood flow to abnormal tangles of blood vessels before they are removed by surgery. The material is delivered to the brain through a tube inserted into a groin artery, known as a catheter. But the catheter can get stuck in the spongy material while inside the brain, causing serious complications including hemorrhage and death, the U.S. …