BOSTON/CHICAGO A leading hospital for implanting mechanical heart devices has suspended use of an experimental heart pump made by HeartWare International Inc HTWR.O after a patient developed a blood clot that caused the device to malfunction, according to a source familiar with situation.
The patient at Aurora St. Luke's Medical Center in Milwaukee, Wisconsin, was treated on an emergency basis with a blood-thinning medication known as tissue-type plasminogen activator (tPA) to break up the clot.
Shortly afterwards, the patient suffered an intracranial hemorrhage while shopping, prompting the hospital to place a moratorium on its trial of the device, known as the HVAD.
Aurora St. Luke's is one of the country's leading centers for mechanical heart assist devices, which are designed to take over the main pumping function of the heart in patients with end stage heart failure. Its action, if replicated at other centers, could have negative implications for HeartWare.
Dr. Andrew Boyle, medical director of the Ventricular Assist Device program at Aurora declined to discuss the case, citing illness. HeartWare declined to comment in detail.
"Information between any one site and the Company is confidential," it said in an e-mailed statement. "As patient safety is our highest priority, if an event occurs at a site, that event is reported to the U.S. Food and Drug Administration as appropriate."
So far reports of device-associated blood clots are not widespread. The HVAD has been approved in Europe, but is still in clinical trials in the United States. It is expected to be approved in the fourth quarter of this year.
"There are going to be issues with any device," said Dr. Valluvan Jeevanandam, Chief of Cardio-Thoracic Surgery at University of Chicago Medical Center. "There may be an incidence of thrombosis, usually related to infection, but not always."
Still, rumblings of concern are filtering through the medical community.
Dr. Babar Chaudhri, a cardiac surgeon at The Freeman Hospital in Newcastle-upon-Tyne in England, said his team exclusively uses HeartWare's device and is very happy with it.
However, reports of device-associated blood clots have caused the group to consider using an alternative device, such as the market-leading HeartMate II device made by Thoratec Corp THOR.O, he said.
"As a group, the feeling at Newcastle is, we're happy with the HVAD," he said. "But it is reasonable to ask whether other devices can more safely deliver the results we're looking for."
SHARES HAVE SURGED
The HVAD is smaller than the HeartMate II and uses a different technology. It is widely considered to be easier to implant than the HeartMate II and many investors believe it will eventually eclipse the HeartMate II.
HeartWare's shares have risen 127 percent over the past year while Thoratec's have fallen 2 percent. The two are similarly valued by the market.
Yet Thoratec is a profitable company with an established product that generated sales of $383 million in fiscal 2010, while HeartWare posted a net loss of $22.4 million, or $1.66 a share in the first nine months of 2010 on revenue of $34.3 million.
"Two years ago everyone thought HeartWare was the future," Chaudhri said. "Now there is equipoise. Now there is a situation where we genuinely don't know if one device is better than the other."
Patients who receive a ventricular assist device typically receive blood-thinning medications to prevent blood clots. Physicians monitor the effectiveness of blood-thinners by using a benchmark known as the International Normalized Ratio, or INR. The higher the INR, the thinner the blood.
Patients who receive a HeartMate II device are typically maintained at an INR level of 1.5 to 1.8, doctors say. The target INR for patients implanted with the HVAD varies, with physicians maintaining a range between 2 and 3. Some physicians, including Chaudhri, maintain INR levels at the higher end of that range.
"It is in response to concerns about thrombosis that we run the INR higher," he said. "The question is, are we subjecting patients to a greater risk of bleeding?"
The risk of thrombosis with left-ventricular devices that use axial-flow technology, such as HeartMate II, is reported to be 0.02 events per patient year, according to a recent article in The Journal of Thoracic and Cardiovascular Surgery. The rate of thrombosis with centrifugal devices such as HeartWare's is not yet known.
In a clinical trial of the device, three patients, or 2.1 percent of the total, with a low INR developed thrombosis. The company did not reveal if any patients with a normal or high INR developed thrombosis.
Dr. Ranjit John, director of the ventricular assist device program at the University of Minnesota, said it was too soon to tell whether there was a significant difference in risk of device-associated blood clots with HeartWare's device.
"There has been less experience with the centrifugal device so it is hard to tell which technology is better," he said. "It is premature to judge which technology has a less favorable influence on thrombosis."
Word that an unnamed high-volume center had imposed a moratorium on the device in January is seeping out to Wall Street. Rajeev Jashnani, an analyst at UBS, dismissed the event in a note to clients after talking to HeartWare's management.
"To treat patient with pump thrombus at a high volume site, HeartWare suggested catheter-based delivery of an anti-clotting agent as an initial therapy," Jashnani wrote.
"However, patient suffered ICH and site placed their participation in HVAD trials on moratorium. Although this site is unlikely to implant HVADs in the near term, we do not believe the issue is widespread or highly problematic."
(Reporting by Toni Clarke; Editing by Ted Kerr)