HeartMate II Blood Clot Problems Highlighted in NEJM

A group of specialists are warning about a potential risk of serious problems with the Thoratec HeartMate II left ventricular assist system (LVAS), which is an implantable heart pump that has been associated with an increased risk of blood clots for those who received the device in recent years.

In an article published in the New England Medical Journal on November 27, doctors from the Cleveland Clinic warn that rates of clot formation rose nearly four times among individuals who have received the HeartMate II since March 2011, compared to those who received the implant in prior years.

The Thoratec HeartMate II LVAS is a coronary implant given to patients whose hearts are too weak to efficiently pump blood. Former Vice President Dick Cheney is perhaps the most famous recipient, but they have been widely used among individuals with advanced heart disease who are waiting for a heart transplant or are too weak to undergo such a procedure.

After examining data from three different hospitals, researchers from Cleveland Clinic were able to identify that over the past few years there has been an increase in the rate of clot formation during the months after the HeartMate II was implanted, confirming what doctors at the hospital suspected based on their own experiences.

“The occurrence of confirmed pump thrombosis increased steeply after approximately March 2011, from 2.2% at 3 months after implantation to 8.4% by January 2013,” the researchers note in their results. “A similar pattern was observed at all three institutions and for multiple surgeons.”

Researchers found 72 incidents of pump-related blood clots in 66 patients. Out of that group, 19 patients had their heart pumps replaced; one of whom died less than a month after the replacement. One patient required three replacements. Another 11 patients required heart transplants, one of whom died. However, 38 patients that suffered pump-related clots were given blood thinners and other medication-based treatments, of whom 19 died, the researchers reported.

Some observers have wondered if Thoratec made some kind of change to the design that could account for the problem, but the manufacturer has maintained that no changes were made that could account for any increase in reports of blood clots.

The FDA has announced it is investigating the findings of the study. Adverse health events linked to problems with the Thoratec HeartMate II should be reported to the company and to the FDA’s adverse event reporting program, MedWatch.

Product liability lawyers are also evaluating potential HeartMate II lawsuits for individuals who have suffered blood clot problems after receiving the heart pump.