(Adds company, panel member comments, background)

By Lisa Richwine

GAITHERSBURG, Md., Nov 30 (Reuters) - Thoratec Corp's <THOR.O> newest implanted heart pump should be approved for keeping patients alive while they wait for heart transplants, a U.S. advisory panel unanimously said on Friday.

The Food and Drug Administration will now decide whether to clear the device, called HeartMate II. The FDA usually follows panel recommendations.

The committee supported the product even though a Thoratec study narrowly missed a pre-specified goal for proving the implant was effective enough. FDA reviewers had asked the panel's input on whether those findings were sufficient.

"I think the sentiment here is that we have met a reasonable assurance of effectiveness," said Dr. Warren Laskey, the panel chairman and a University of New Mexico cardiologist.

The panel, a group of experts from outside the FDA, urged the agency to require a post-approval study to gather more information about bleeding episodes and others issues.

The HeartMate II and similar implants, known as left ventricular assist devices, are designed for people with severe congestive heart failure and few medical options.

Older versions are too bulky for many women and some smaller men. The HeartMate II is smaller than Thoratec's other models, about the size of a D battery, making it a possible option for a wider range of patients.

A company-funded study of 126 patients showed a 64 percent success rate for the HeartMate II device, just below a pre-specified goal of 65 percent, FDA reviewers said.

Success was defined as surviving until a transplant or living at least 180 days while waiting for a donor heart.

Thoratec said an alternative analysis showed stronger results. That analysis counted patients as successful cases if they had the device implanted and were eligible for transplants but were not on a waiting list for various reasons.

The company's overall data "demonstrate a reasonable assurance that HeartMate II is safe and effective by all clinical measures evaluated," Thoratec Vice President Donald Middlebrook told the panel.

Potential complications included bleeding and infections, which FDA reviewers said were in line with other similar devices. Some panel members, however, voiced concern that 29 percent of patients required an operation to control bleeding.

The panel also said it was unclear how smaller patients would fare with the device because there were not enough of them in the study to draw conclusions. The experts urged Thoratec to look closely at smaller patients in the post-approval study.

"We need more data in this group," Laskey said.

World Heart Corp <WHT.TO>, Ventracor Ltd <VCR.AX> and MicroMed Cardiovascular Inc <MMCV.OB> make similar heart-assist implants. (Reporting by Lisa Richwine, editing by Gary Hill)

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