The FDA has allowed Direct Flow Medical to expand its pivotal trial to include high-risk patients, more centers and comparison with a commercially available transcatheter aortic valve replacement (TAVR) valve.

The SALUS (TranScatheter Aortic Valve RepLacement System a US Pivotal Trial) clinical study initially recruited 11 centers in the U.S. and one in Italy to enroll about 600 patients with severe aortic valve stenosis who are considered unsuitable for surgery. It is designed to assess safety and effectiveness based on the composite of all-cause death and disabling stroke at 12 months. The trial also will evaluate severe and moderate paravalvular regurgitation at 30 days.

In an Investigational Device Exemption, the FDA widened the pool to up to 45 facilities in the U.S., allowed the addition of high-risk patients and randomization to Medtronic’s CoreValve. That is expected to increase the number of participants to more than 900, according to Direct Flow Medical.

The self-expanding CoreValve device has been approved for both patient populations in the U.S. Recently released two-year results for CoreValve have shown it to be superior to surgery in high-risk patients.

CoreValve and Edwards Lifesciences’ Sapien valves are the only approved TAVR devices in the U.S. The Direct Flow Medical system received the CE mark in January 2013 but it remains investigational only in the U.S.