WASHINGTON (Reuters) - U.S. medical device reviewers said HeartWare International Inc's blood pump seemed to help people with severe heart failure, but concerns were raised about device-associated clotting rates and stroke.
U.S. Food and Drug Administration staff also said clinical trial results for the mechanical heart-assist device, or the HeartWare ventricular assist device (HVAD), may have missing data and are difficult to compare with a registry of patients.
In clinical trials, HeartWare compared patients who got its device to a registry, or database, of patients with mechanically assisted circulatory support. It was the first blood pump trial to use a registry as a control arm.
The FDA said 16 of the 250 people implanted with HeartWare's device had blood clot-related pump failure, and 15 of them needed to exchange their pumps.
"Due to concerns regarding missing data, treatment and control group comparability, device exchange and neurological (stroke) event rates, the data require careful consideration of what clinical conclusions can be drawn," the FDA staff said in documents posted online on Monday.
HeartWare's device helps a severely weakened heart pump blood while awaiting a heart transplant. It is already approved in Europe.
It is estimated that some 50,000 people around the world are candidates for heart transplant, but only some 5,000 patients per year get them.
The FDA staff review comes ahead of a meeting of outside experts who were due to vote on the device on Wednesday. The FDA will make a final decision later.
If approved, the device will compete with Thoratec Corp's HeartMate II, which has been sold in the United States since 2008.
(Reporting by Anna Yukhananov; Editing by Gerald E. McCormick and Maureen Bavdek)