NEW YORK (CBS 2) — More than two million Americans suffer from an irregular heartbeat, known as atrial fibrillation. That puts them at increased risk for devastating strokes.

For decades, doctors have had just one blood-thinning drug to help them, but as CBS 2HD’s Dr. Max Gomez reports, there’s a revolutionary new drug just approved by the FDA.

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Atrial fibrillation can cause blood clots to form in the heart. Those clots can break loose and go to the brain, causing a stroke, which is the country’s leading cause of serious disability.

A-fib patients are usually prescribed a blood thinner called warfarin or coumadin, but their blood levels have to be checked constantly, sometimes weekly, since too much coumadin could cause serious hemorrhaging.

The new drug is welcome news.

Hernan Guarderas, 68, was hoping a new blood thinner will give him back his old life. It’s called dabigatran. “With this new medicine, I would be free.”

Hernan is an a-fib patient, and has been taking the common blood thinner warfarin, also called coumadin, to prevent a  stroke. The drug forces him to restrict his diet, increases his risk of  bleeding, and requires very close monitoring.

“I was for almost two years, every week at the doctor’s office taking my blood,” he said.

The new drug does not require monitoring. It’s also easy to stop if the  patient needs surgery. “The cardiology community has been waiting for  years to have a replacement for warfarin,” said cardiologist Dr. William Borden.

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A study of more than 18,000 patients found that dabigatran, available in two  strengths, prevents more strokes or causes less bleeding, depending on the  dose. The most common side effect was intestinal upset.

“It seems like this could really be a revolution in how we treat patients with atrial fibrillation,” Borden said.

This drug will be more expensive than warfarin.  Another concern is that there were more heart attacks in patients taking dabigatran.

“Although there was an increased risk of heart attacks in the  study, I think our worry clinically is more about strokes and so that will probably not be a big factor in deciding which of these two blood thinners to use,” said Dr. Christopher Cannon of the Brigham and Women’s Hospital.

Dr. Gomez spoke with cardiologists, arrythmia experts and stroke experts, and they’re all very excited about dabigatran or predaxa.

Coumadin is all they’ve had to prevent strokes in a-fib patients for 50 years. It’s a life-saving but difficult drug to keep take.

Patients need constant testing to make sure levels stay high enough to prevent blood clots  but not so high as to lead to serious bleeding.

So this could turn out to be a blockbuster drug.

And here’s the relationship between a-fib and blood clots: with a-fib, the upper chambers of the heart don’t beat effectively so blood tends to pool or stagnate in the atria, the two upper chambers. Blood that’s not moving starts to clot and those little clots in the heart can break off and then flow either to the lungs or if they go to the brain, they can cause a stroke.

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A-fib causes about 15-fifteen percent of all strokes and they are twice as likely to be fatal as other causes of stroke.