Shares of NMT Medical lost a third of their value Monday after a study failed to prove the company’s device for closing a small hole in the heart can prevent migraine headaches in some patients.

The hole, a common heart defect called a patent foramen ovale, has been linked to being a risk factor for migraine headaches.

The Boston-based company had hoped the double-blind study would show its device could eliminate headaches in 40 percent of 147 study participants within six months. Instead, the so-called MIST study showed 37 percent experienced a reduction in migraines.

"We were disappointed that MIST did not satisfy its endpoints,” said NMT’s CEO John Ahern.

NMT shares tumbled $6.88 to close at $14.04 on trading of 8.9 million shares, or more than a dozen times their average daily volume.

To be sure, the primary investigator, Peter Wilmshurs, said the study did show significant effects using NMT’s device to treat certain types of migraines. And Mr. Ahern said the data will help future research.

Coronary Quest

In addition to causing migraines, the holes could allow unfiltered blood to enter the circulatory system. If the blood contains a clot or other debris, it could trigger a stroke.

allow unfiltered blood to enter the circulatory system. If the blood contains a clot or other debris, it could trigger a stroke.

And NMT isn’t the only one developing devices and techniques to seal the holes. Medical device maker St. Jude Medical is among the large companies working on a closure device.

edical device maker St. Jude Medical is among the large companies working on a closure device.

Startups are also trying to bring new innovation to the market, like Redwood City, California-based Cierra, which is working to reduce migraines by closing the hole with a non-implant, catheter-based technology.

In June, Cierra grabbed $21 million in venture backing. The company said funding will be used primarily to launch clinical trials and develop the product. Delphi Ventures led the financing. Morgenthaler Ventures, Split Rock Ventures, and Frazier Healthcare Ventures also contributed.

Delphi