Nope, we’re not talking about the super-hero comic book movie the Watchmen. Our villains are of a different sort — the stroke causing thrombi that form when you’ve got atrial fibrillation.
Over the past couple of years, we’ve been following the development of a medical device called the Watchman (see here, and here), made by Minnesota based AtriTech, Inc. The Watchman is an implant that occludes the left atrial appendage in the heart in hopes of preventing strokes for those with afib.
To recap, when you’ve got atrial fibrillation, blood can pool in the left atrial appendage of your heart, an area that most current evidence shows isn’t at all needed (it’s a bit like the appendix of the heart). When this happens, thrombi (clots) can form and if they dislodge, can cause life-threatening strokes. To cope with this risk, most patients with atrial fibrillation need to take an anticoagulant such as coumadin their entire lives. These medications are tough to dose, can put the patient at risk for hemorrhage, and require regular visits to the doctor.
The idea behind the Watchman is to simply block the opening of the troublesome appendage with a mesh, squid-looking stent so that the clots that do form cannot escape and cause trouble elsewhere. This actually ends up clotting off the whole appendage behind the device, which is also expected to epithelialize.
Clinical trials of the device, however, had until now been on the smaller scale (there was a pilot study with about 30 people in 2007). The results of a new, larger study just announced at the American College of Cardiology’s annual meeting indicate that the device indeed has great promise as an alternative to anticoagulant therapy.
The study looked at 707 patients, 463 who got the device, and 244 who didn’t. Of those who got the Watchman, there were 15 strokes and 17 deaths. Of those who didn’t and were treated with coumadin, there were 11 strokes and 15 deaths. This amounts to an approximate 3% risk of clot related problems with the device and 5% without, though complications were more common with the device (8% vs 4%).
The moral of the story seems to be that there is a greater up-front risk from the procedure, but 90% of the patients with the device were able to go off of coumadin completely, and the device appears to function at least equally well as the medication. Great news for AtriTech and patients with atrial fibrillation.
An FDA advisory panel is meeting at the end of next month (April ’09) to consider AtriTech’s application.
From MedPage Today:
While the Watchman’s overall advantage met noninferiority criteria, the 91% reduction in the hemorrhagic stroke rate (0.2% versus 1.9%) met superiority criteria, they reported at the American College of Cardiology meeting here. However, these benefits in the randomized PROTECT-AF trial came at the price of twofold higher risk for complications (8.7% versus 4.2%), predominantly early pericardial effusion….
But Dr. Holmes cautioned against discounting patient preference. "If you ask patients in a heart clinic, the one medication they always want to get off is always warfarin."…
Researchers plan a five-year follow-up, but there’s little reason to suspect that the effects won’t last, Dr. Holmes said. The left atrial appendage clots off behind the device, which is expected to epithelialize as well…
There were some dislodgements, according to the report. Two occurred in the pilot phase before improvements in design. Another occurred during the main phase of the trial, several months after placement. In that case, the patient was asymptomatic, and doctors discovered the device missing serendipitously during echocardiography. They later retrieved it from the abdomen.
The dislodgement rate may be one in 350 or 400, Dr. Holmes estimated.