Helping the heart pump but battling blood clots

HeartMate II external equipment (Photo courtesy Thoratec)
HeartMate II external equipment (Photo courtesy Thoratec)

For years, the HeartMate II - made by Thoratech - has been a go-to medical implant for patients with heart failure. The pump, called a left ventricular assist device, keeps patients alive long after their hearts stop working properly.

But in early 2011, doctors at the Cleveland Clinic noticed that patients implanted with the device were suddenly getting blood clots, or what the surgeons call pump thrombosis. And the patients who developed the thrombosis were nearly 50 percent more likely to die if the doctors didn't replace the device or find a new heart.

"Every device that we use has a set of risks and adverse events. Some have more stroke, some have more pump thrombosis," said Dr. Randall Starling, vice chairman of cardiovascular medicine and section head of heart failure and cardiac transplant medicine at the Cleveland Clinic, is lead author of a multi-center study on the HeartMate II.

The study notes that of 837 patients implanted with the device at three institutions - the Clinic, Duke University Medical Center and Washington-Barnes Jewish Hospital in St. Louis - all reported similar adverse results.

Starling says the Clinic immediately notified Thoratec and the U.S. Food and Drug Administration of its findings. But the Clinic won't necessarily stop using the HeartMate II. Instead, he says, they will be more careful.

"Now that we have this knowledge of the HeartMate II, I think we're able to make more informed decisions on the most appropriate pump in a specific patient and, even more importantly, how to monitor those patients and to anticipate the treatment options and to provide informed consent to a patient encompassing all of this information," Starling says.

The FDA approved use of the HeartMate II in 2008 after years of successful clinical trials, and it is the most widely used device of its kind, with 16,000 implants worldwide.

In response to the clinic's study, the company notes that blood clots are a known complication with implants. And it points to another report that found the six-month survival rate of patients has remained consistently high at 86 percent since the device came on the market.

Dr. Abeel Mangi, an associate professor of surgery at Yale University School of Medicine, says the Clinic study is another in a line of papers that connects blood clots with the implanted devices. But, he says, that should not detract from the fact that thousands of lives have been saved by the use of ventricular assist devices.

"You know, it's partly because of that success that we're now actually in the position to have meaningful discussions about you know what we would sort of consider to be second-tier outcomes such as pump thrombosis and things of that nature because we've really crossed the hurdle of survival," Mangi says.

Mangi discloses that he was a paid speaker for Thoratec in the previous year. The Clinic's Dr. Starling was a consultant for the company this year, but asked that his fees be donated to not-for-profit causes or to the Cleveland Clinic to support research and education.

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