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Study: HeartMate II Tied to Increased Clot Risk

Dec 2, 2013

The cardiac device HeartMate II has been tied to an increased risk of blood clots, according to newly published research regarding the left ventricular assist device.

The HeartMate II has been associated with a spike in thrombosis (blood clot) rates in patients implanted with the device, according to a New England Journal of Medicine (NEJM) November 27th report, reported. Shares of Thoratec Corp., the maker of the device, dropped following publication of the study results.

The HeartMate II falls into the category of products known as a left ventricular assist devices—or LVADs. The device is constructed with a pump that continuously pushes blood through the heart, according to The New York Times.

The research examined data from the Cleveland Clinic, the Washington University Barnes-Jewish Hospital, and Duke University Medical Center. Together, the three centers implanted 895 HeartMate II LVADs in 837 patients from January 2004 through May 2013, according to A total of 72 confirmed cases of pump thrombosis were discovered in 66 patients; another 36 suspected cases of pump thrombosis were also found, according to the NEJM study.

The study authors noted that "The occurrence of confirmed pump thrombosis increased steeply after approximately March 2011, from 2.2 percent … at 3 months after implantation to 8.4 percent," adding that "a similar pattern was observed at all three institutions and for multiple surgeons," according to the report.

The research also pointed to a similarly sharp decline in the time from HeartMate II implantation to blood clot development—from 18.6 months to 2.7 months, according to Increased levels of lactate dehydrogenase (LDH) were also found to precede confirmed cases of blood clots. This means that LDH levels might work as a marker for the HeartMate II thrombosis risks.

According to the researchers, a build-up of both fibrin and a denatured protein that accumulates near the HeartMate II's inflow bearing could be responsible, in part, with clot formation, according to the NEJM study, wrote

Cleveland Clinic physicians began seeing issues with the implant in 2012, according to The New York Times. The device is used to treat patients diagnosed with advanced heart failure, such as what was seen in Vice President Dick Cheney. The number of patients who developed the potentially deadly blood clots following implantation with the device was on the rise, prompting researchers to review hospital records earlier this year, at which time they became very concerned.

The incidence of blood clots in HeartMate II patients who were implanted after March 2011 was almost four times greater than what was seen in patients who were implanted with the device before March 2011, according to The New York Times. In patients who did not die, pump-related clots that called for emergency measures required heart transplants or device replacements. “When we got the data, we said, ‘Wow,’ ” Dr. Randall C. Starling, a cardiologist at Cleveland Clinic, told The New York Times.

In a statement, the U.S. Food and Drug Administration (FDA) indicated that it was in the process of reviewing the study’s findings. “The agency shares the authors concerns about the possibility of increased pump thrombosis,” the agency indicated.

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