Boston Scientific's Watchman closed in on a $2 billion year in 2025, with more than 800,000 implants worldwide. The pitch is simple: seal a pocket in the heart so a clot is less likely to form and travel to the brain. The harder question is whether that implant should replace a blood thinner a patient can still take.
In a Spotlight report published Thursday, The Boston Globe said recent trials found Watchman often no better, and in some cases worse, than a time-tested blood thinner. The company has kept up the sales pitch anyway, on television and through paid physician teaching.
What the Device Is Built to Do
Atrial fibrillation scrambles the rhythm in the heart's upper chambers. More than 10 million Americans have been diagnosed with it, the Globe reported, and the condition multiplies stroke risk by five. Clots can collect in the left atrial appendage, a small pouch off the left atrium. Watchman is built to close that pouch.
An FDA labeling excerpt says the device is indicated to reduce the risk of thromboembolism from the left atrial appendage in patients with non-valvular atrial fibrillation who are at increased risk of stroke and systemic embolism and who are recommended for anticoagulation.
After an extended FDA debate, Watchman was eventually approved for a limited group.
The FDA labeling says physicians who implant the device must complete training. Boston Scientific reports major complications in 0.5 percent of patients, counting events within a week of the procedure or discharge. That window is the company's, and it is short.
The other side of the choice has its own emergency-room math. The Globe reported that U.S. emergency departments receive about 300,000 people a year for bleeding related to blood thinners. Kenneth Stein, Boston Scientific's global chief medical officer, has estimated that 30 to 40 percent of people with atrial fibrillation cannot or will not take those drugs. In a company interview the Globe described, he called Watchman a proven alternative to them.
A National Campaign and a $2 Billion Year
The television campaign went national in 2019, after pilots in Tampa, Detroit, San Diego, and Phoenix, the Globe reported.
People who saw a commercial were six times more likely to ask their doctors about the device. That tracks questions, not implants.
By 2017, Boston Scientific had at least 200 Watchman specialty centers in the United States.
Watchman sales alone reached nearly $2 billion in 2025, up some 30 percent from the year before.
The parent company had 2025 net sales of $20 billion and 59,000 employees.
Two Trials, Two Different Bars
CHAMPION-AF followed 3,000 patients for three years. The Globe reported that Boston Scientific funded it. American College of Cardiology coverage said Watchman FLX met the trial's noninferiority criterion against anticoagulant therapy on the primary efficacy endpoint, which occurred in 5.7 percent of the device group and 4.8 percent of the drug group. The Globe described that measure as a combination of cardiovascular death, stroke, and systemic embolism.
Noninferiority means the implant stayed inside a margin the study set in advance. The device arm's rate was still the higher of the two. Clearing the bar is not the same thing as beating the pills.
Bleeding went the implant's way. At three years, nonprocedural bleeding was reported in 10.9 percent of device patients and 19.0 percent of patients on anticoagulants, a difference the ACC summary said met superiority. Ischemic strokes went the other way: 3.2 percent with Watchman FLX and 2.0 percent with anticoagulants. That difference wasn't statistically significant.
CLOSURE-AF, presented at the American Heart Association's 2025 Scientific Sessions, asked the question in patients at high risk of both stroke and bleeding. It didn't show that left atrial appendage occlusion was noninferior to standard care, TCTMD reported. One trial cleared its margin. The other, in a higher-risk group, did not.
Critics Say Most Patients Are Not the Market
Dr. Gregory Marcus told the Globe, "I don't think it's responsible medical practice to push for such a device in the great majority of A-fib patients." Commenting on CHAMPION-AF for the American College of Cardiology, he said the data are insufficient to conclude that this approach is "broadly as effective as standard NOAC therapy for most patients with AFib." NOAC is the trial shorthand for the anticoagulant arm.
Stein's 30-to-40-percent estimate is the company's account of who cannot or will not stay on a blood thinner. Marcus is talking about the great majority who can.
Marcus has said the evidence doesn't support making Watchman a first-line treatment.
The Pitch Is Still Pointed Outward
On a 2025 investor call, chief executive Mike Mahoney called Watchman a gem for Boston Scientific.
A patient who can still take a blood thinner is looking at a narrower record than that sales story. In CHAMPION-AF, Watchman FLX met a noninferiority test and had less nonprocedural bleeding. Ischemic strokes were more common with the device, 3.2 percent versus 2.0 percent, and that difference wasn't statistically significant. For patients at high risk of both stroke and bleeding, CLOSURE-AF didn't show that occlusion was noninferior to standard care. Medicare pays about $25,000 for the procedure. The ad estimates have not come down with the caveats.
