Thank you for the opportunity to speak today. I am Dr. Christina Silcox, I have a PhD in Medical Engineering and Medical Physics from MIT, and I am a senior fellow at the National Center for Health Research. Our research center scrutinizes scientific and medical data and provides objective health information to patients, providers and policy makers. Those are the perspectives I bring with me today. We do not accept funding from device companies and so I have no conflicts of interest.
We all know that AF patients are at high risk of ischemic stroke. Warfarin is well-established as an effective treatment, and other new therapies provide safe and effective alternatives. Any new treatment should show clear evidence that the benefits outweigh the risks.
Like many of you, we are skeptical that the Watchman device achieves that goal.
The PREVAIL trial shows that the Watchman device is inferior to warfarin for 2 of the 3 primary endpoints. Ischemic strokes and systemic embolisms occurred at higher rates in the Watchman group compared to the control group.
Most troubling, most of the ischemic strokes occurred more than one year after implantation. In the PREVAIL study, twice as many patients experienced an ischemic stroke or systemic embolism in the second year after implantation than in the first year. Longer-term data is clearly needed to determine if the device is losing effectiveness or if the device itself is causing these events. While the PROTECT AF data include 5 years of follow-up, many implanted patients also took oral therapies, confounding the results. The sponsor’s proposed post-market study includes only 2-year endpoints and lacks a control group. That is not adequate to evaluate long-term safety or effectiveness of a permanent implanted device. And it is unclear what chronic antiplatelet drugs would be allowed in this post-market study, which would lead to the same analysis issues as the PROTECT AF study.
The major potential benefit of the Watchman device is a decrease in hemorrhagic strokes. Unfortunately, the small number of patients in the PREVAIL study and the low incidence of hemorrhagic strokes means the results are inconclusive. The problematic PROTECT AF trial did show a decrease in the incidence of hemorrhagic strokes, but the control group had more hemorrhagic strokes than other warfarin studies, so we can’t draw conclusions.
The PREVAIL trial shows fewer major bleeding events after 6 months post-implant, but Watchman patients had major bleeding related to the surgery, which makes up for the lower bleeding rate later. Longer-term data is needed to determine if this is a risk or a benefit.
We are glad to see that additional training may reduce the rate of complications from surgery, but since clinical trials tend to include the best physicians it would be unrealistic to think that most AF patients would find surgeons with that level of training and expertise.
In summary, patients implanted with the device are at increased risk for ischemic stroke. Methodological problems make it difficult to assess if the device reduces hemorrhagic strokes. The decrease in major bleeding events after 6 months is negated by the increased major bleeding events due to surgery. The device is inferior to warfarin for 2 of the 3 primary endpoints identified by the sponsor and the FDA as signifying success.
That’s why we urge you to vote NO — the data do not prove that the benefits outweigh the risks or provide a reasonable assurance of safety or effectiveness.