In a closely watched clinical trial, Boston Scientific’s promising-but-delayed Lotus heart valve performed well in a head-to-head study comparing it with a popular device from Medtronic, according to data presented Tuesday at an industry conference in Paris.

The international, randomized controlled trial, funded by Boston Scientific, found that high-risk aortic stenosis patients who got the experimental Lotus device had a lower combined rate of death, disabling stroke and valvular leakage one year after the device was implanted than patients who got a version of Medtronic’s CoreValve device.

In particular, the rate of leakage around the edges of the Lotus valve was significantly lower, as was the rate of disabling stroke after one year. But the Lotus device showed a much higher rate of patients needing a pacemaker within 30 days of the valve implant.

The positive results for the Lotus device drew praise from stock analysts Tuesday, who said the results should portend well for Boston Scientific as the company works toward Food and Drug Administration approval for the heart device late in 2017, and commercial launch by mid-2018. The device was pulled off the European market earlier this year, and the U.S. launch was pushed back, because of glitches with how the doctor deploys it inside the heart.

Medtronic, which did not directly participate in the study, raised some doubt about the findings.

A Medtronic spokesman noted that the study used a first-generation version of Medtronic’s minimally invasive aortic valve, not the latest iteration that benefits from design improvements. Tuesday’s findings were not consistent with results reported in Medtronic’s own pivotal trials for its CoreValve devices.

Traditional aortic replacement heart valves are permanent, inflexible mechanical devices. The newer “transcatheter” versions fold up into a long catheter the size of a drinking straw that is inserted into a major blood vessel, often the femoral artery in the leg, and advanced to the heart using live motion X-rays. The recovery time is supposed to be shorter, and the device prices higher.

Transcatheter valves are expected to make up a $5 billion global market by 2021. They are mainly used in patients with severe aortic stenosis now, though sales could grow as usage spreads among less-sick patients.

Only two companies’ devices are approved for the U.S. market — Medtronic’s CoreValve and Edwards Lifesciences’ Sapien valve system. Doctors have said the introduction of a third device to the market is likely to create more price competition.

On Tuesday, physicians at the annual EuroPCR conference in Paris presented one-year study data that found about 17 percent of the 600 people who were randomized to the Lotus device had either died, had a disabling stroke or had at least moderate leakage around the edges of the valve.

That compared to 29 percent of the 300 patients who had those outcomes with Medtronic’s CoreValve device in the same period of time.

The average patient age was 83. Patients in the study had severe aortic stenosis and at least class II heart failure.

Although patients with the Lotus device had slightly lower mortality, the differences in performance were mainly driven by the contrasts in leakage around the valve (2 percent vs. 11 percent) and disabling stroke (4 percent vs. 7 percent), the data show. The Lotus has an “adaptive seal” around the base where it connects to the heart.

“The excellent results seen in this large randomized trial, particularly the superior performance in efficacy and the continued demonstration of low PVL (para-valvular leakage) rates, further establish the advantages of the Lotus valve system,” study co-investigator Dr. Ted E. Feldman of NorthShore University HealthSystem in Illinois said in a statement.

About 29 percent of the Lotus patients had a permanent pacemaker implanted within 30 days of their new valve, compared to 16 percent of the CoreValve patients. Newer iterations of the Lotus device have a “depth-guard” feature that is intended to cut the number of pacemakers needed by Lotus patients after surgery.

A spokesman for Medtronic questioned the finding on disabling strokes, which were higher in Boston Scientific’s study of Medtronic’s device than in Medtronic’s own studies of its minimally invasive aortic valves. One of the presenters in Paris noted Tuesday that the stroke statistic was “probably a chance finding,” the Medtronic spokesman said.

“Given all the limitations and unknowns surrounding this study right now, we trust that the physician community will further evaluate the study findings when this is published in a peer review journal and make their own determination of the study’s clinical relevance,” the Medtronic spokesman said via e-mail.