A tiny wire and mesh device to prevent strokes, first doodled on a napkin by a pair of Minneapolis cardiologists, is a step closer to regulatory approval and to what analysts estimate will be a $1 billion market.

The Watchman, which helps stave off strokes by plugging a cul-de-sac in the heart where clots form, will go before an advisory panel of the U.S. Food and Drug Administration on Dec. 11. The product was developed years ago by a small Minneapolis company and was purchased three years ago by Boston Scientific Corp.

In patients with atrial fibrillation — a disorder that interferes with the heart's rhythm — blood can pool in the left atrial appendage and clots can form. The clots can then migrate to the brain and cause stroke. The Watchman will help prevent this because plugging the appendage will stop clots from traveling.

Data from clinical trials and from years of tracking patients show the device not only reduces the risk of stroke, but that it may be a better option for patients who shouldn't take blood-thinning medications. Currently, medication is the only way doctors have to combat the chance of stroke in those patients. All of which is excellent news to Dr. Robert Schwartz and Dr. Robert Hauser, cardiologists with the Minneapolis Heart Institute Foundation, who came together on the idea nearly a decade ago.

"My goal in life is to replace drugs with devices," Schwartz said.

Said Hauser: "This is really going to change things for patients. … The only real disappointment is that it's taken so long."

The device, which looks like a tiny parachute, is inserted into the heart with a catheter that snakes through a blood vessel in the leg. Once inside the heart, the device is placed in the left atrial appendage, a small pocket off the left atrium.

Once the device is implanted, tissue grows over it and permanently closes the area: no more clots, and no need for years of blood thinners that can carry their own risks over time.

Schwartz and Hauser, along with Dr. Robert Van Tassel, were among a group that formed a small start-up company called Atritech years ago and began applying for FDA approval. In 2011, Boston Scientific bought Atritech for up to $375 million and the Natick, Mass., company has been carrying the torch ever since. Its most recent data, released in May, showed the device was superior to blood thinners in preventing stroke in atrial fibrillation patients.

Dr. Bill Katsiyiannis of the Minneapolis Heart Institute has repeatedly implanted the device in patients. He has no financial stake in the device, yet is a clear champion for using it on atrial fibrillation patients who have a risk of stroke, but for whom blood thinners are not a good option. This is the way to go for those people," he said. "It fills a very specific need, and it's a big need."

Mary Hacker, 74, of Minneapolis, is one of those patients. She has atrial fibrillation and high blood pressure. Three years ago, she had a stroke. Nearly two years ago, her doctors recommended having the device installed to prevent another stroke. She was out of the hospital in a day and has not taken a blood thinner since.

"It's been wonderful," she said. "I was very pleased with the whole program."

Watchman's road has not been completely smooth. The FDA conducted an earlier advisory committee meeting in April 2009 and voted 7-5 in favor of approval. But the agency also had concerns and wanted another study. After much more time and expense, that was recently completed.

Analysts, doctors and officials at Boston Scientific are predicting FDA approval in the first half of 2014. It is a promising market. In a note to investors, analyst Lawrence Biegelsen of Wells Fargo said he expects worldwide sales of the device, which has been on the market in Europe for a couple of years, to go from $30 million in 2013 to $162 million in 2014. Wedbush analyst Tao Levy wrote to clients that "We view Left Atrial Appendage [LAA] closure as a $1 billion market opportunity."

Dr. Kenneth Stein, chief medical officer for cardiac rhythm management at Boston Scientific, is cautious when talking about the market potential for Watchman. The company has said it could eventually be a $500 million market — after a carefully controlled rollout. But what Stein is not cautious about is what the device means to patients.

"I hope everybody recognizes how big the unmet need is for this device," he said.