* Device safety improved versus earlier trial results
* Rate of death, stroke, complications within 7 days 4.6 pct vs 8.7
* Boston Scientific to use data to seek U.S. approval
SAN FRANCISCO/CHICAGO, March 9 - A tiny upside down umbrella-shaped device implanted on the heart to prevent stroke in patients with a dangerous irregular heart rhythm known as atrial fibrillation appeared to be safe in a highly anticipated clinical trial, providing an alternative to clot-preventing blood thinners.
The device, called Watchman and made by Boston Scientific Corp, could potentially spare heart patients a lifetime of taking anticoagulant drugs, such as warfarin, that carry a high risk of bleeding.
The Watchman, which Boston Scientific acquired when it bought Atritech in 2011, has been available in Europe for several years. But U.S. regulators wanted another safety study, testing it in higher risk patients, before considering approval in the world's biggest market.
"In this experience focusing on safety, we were very, very pleased," Dr. David Holmes, a cardiologist at the Mayo Clinic who led the study, said in an interview.
People with atrial fibrillation, the most common type of arrhythmia, are five times more likely to suffer a stroke than those without the condition. It affects nearly 3 million people in the United States and that number is expected to increase.
The study, dubbed Prevail, was a follow-up to a previous study called Protect-AF, which demonstrated that Watchman works as well as warfarin in preventing clots that cause strokes.
But the U.S. Food and Drug Administration raised concerns about complications, such as build-up of fluid around the heart and stroke around the time of the procedure, explained Holmes, who also led the earlier trial. The latest study compared safety data between the two trials.
"Absolute stroke rates were low, but statistically they were less in this group of patients treated in Prevail" even though they were higher risk patients, Holmes said.
The 407-subject Prevail trial enrolled more diabetics than the previous study, patients who were older and were deemed at higher risk of stroke or had suffered a previous stroke. And still, stroke rates were statistically significantly lower in the Prevail study, procedural success was higher and vascular complications were lower, Holmes said.
In one of the primary goals of the study, a composite of rate of death and serious complications related to the procedure - cardiac perforation, stroke, blood clots at the device site and fluid buildup around the heart - within seven days of implantation, Prevail results were statistically significantly better than in the earlier trial - 4.6 percent compared with 8.7 percent.
"I was delighted," Holmes said of the results.
The data was released at the American College of Cardiology scientific meeting in San Francisco, but a formal presentation of the results scheduled for Saturday was canceled by the ACC after Boston Scientific inadvertently broke an embargo by sending around a press release early.
In another study goal, looking at rates of death, stroke and systemic blood clots after 18 months of follow-up, there was no difference between the two studies, researchers said.
The latest study also looked at the effectiveness of new training programs and found little difference in results between doctors who had experience with the procedure and newly trained physicians.
Boston Scientific plans to use the data to seek U.S. approval for Watchman.
Researchers said the device could prove to be a good option for younger heart patients.
"Although bleeding rates with some of the new drugs are better than with warfarin, if you are a 50-year-old person and you are going to be on a drug for 30 years, the longer you are on a drug that is an anticoagulant, the more your chance of bleeding," Holmes said.
It is also seen as a possible alternative for older, more frail patients at risk of bleeding from a fall or other accident. "We see a fair number of people that are a little unsteady on their feet. Your balance is not quite what it used to be. That's a very real issue," Holmes said.
The Watchman is implanted using a thin catheter and secured on the left atrial appendage, a thumb-sized muscular pouch connected to the left atrium of the heart. The device captures clots, preventing them from being dislodged and moving to the brain.
Larry Biegelsen, an analyst with Wells Fargo, estimates U.S. Watchman sales of $104 million in 2017, representing about 2 percent of Boston Scientific's total sales.
Any positive news should be most welcomed by the company and its shareholders. Boston Scientific has been struggling, in part due to weakening demand for its main products - heart stents and implantable heart defibrillators and pacemakers - and its stock has been trading in the single-digit range for more than three years. It closed at $7.49 on Friday.