AF Symposium 2015
by Steve S. Ryan, PhD, February 2015
The Watchman device is in the last stages of the approval process from the FDA. This is a true “tipping point” in the development of devices to help A-Fib patients (The Watchman is approved everywhere else in the world). If (or rather when) the Watchman is approved in the U.S., it will be because of the dedicated, thorough research of Dr. Vivek Reddy and his many colleagues and researchers.
Dr. Vivek Reddy of Mount Sinai Hospital gave a historically important talk entitled “5 Year Follow-Up Data On Watchman in Coumadin Eligible Patients.” He discussed the two major clinical trials of the Watchman device—PROTECT-AF and PREVAIL.
In PROTECT-AF, patients who were followed for five years had less strokes (Primary Efficacy Endpoint) than those in the warfarin arm and there were less deaths. (Reddy, V. et al. JAMA. 312:1988 )
The PREVIAL clinical trial was a smaller study designed to confirm the results of the PROTECT-AF trial and validate the safety of the implant procedure. With regards to the Primary Efficacy Endpoint (composite of all stroke, systemic embolism, and cardiovascular/unexplained death at 18 months), “non-inferiority was not achieved.” In other words, the Watchman group performed slightly worse than the warfarin control group.
But for some reason the warfarin control group performed much better than in any other trial. The Ischemic Stroke Rate per 100 patient-years was 1.1 in PROTECT-AF, while in PREVAIL it was only 0.3. In other words, the warfarin control group in PREVAIL overperformed compared to any other clinical trial.
Dr. Reddy pointed out to the FDA panel October, 2014 that the longer-term follow-up of the PROTECT-AF trial confirmed the efficacy of the Watchman therapy, even though the PREVAIL trial trended negative compared to the warfarin control group. But this particular PREVAIL warfarin control group was “unusual” and performed much better than expected.
Looking at other adverse events, the hemorrhagic stroke rate was 0.4% for the Watchman arm and 0.7% for the warfarin control group.
The Cardiovascular Death rate was 1.4% for the Watchman vs. 2.3% for warfarin.
Combining PROTECT-AF and PREVAIL
When you combine the PROTECT-AF and PREVAIL studies even with the “unusual” PREVAIL warfarin control arm results, “All Stroke” is non-inferior or about the same for both arms.
Also, as one would expect, after 6-months post implant, the Watchman arm had significantly less bleeding events than warfarin.
Early Safety Endpoint Achieved
The Early Safety Endpoint in PREVAIL was achieved.
• There was a significant increase in inplant success rate (95.1%) compared to PROTECT-AF (90.9%). There was no significant difference in complication rates between experienced and new implanters, demonstrating the success of the physician training program. Following successful implantation, 99.3% of patients were able to discontinue warfarin after 12 months.
• There was a 52% reduction in procedure/device related vascular complications (1.9% in PREVAIL vs, 4.0% in PROTECT-AF).
• There was a 52% reduction in pericardial effusions requiring intervention and at a rate comparable to other left atrial procedures.
Because of a freak statistical accident, the warfarin arm in the PREVAIL trial performed much better than expected and much better than in any previous trials. Perhaps if the PREVAIL trial were longer or had more subjects, the results might approach the longer PROTECT-AF trial. One shouldn’t interpret the results of PREVAIL as negating the conclusive results of the longer PROTECT-AF trial. In PREVIAL the Watchman device performed just as well as in PROTECT-AF. Only the warfarin control arm was different.
The most significant finding of PREVAIL was the the Early Safety Endpoints were achieved. That was the primary reason the FDA wanted the PREVAIL study in the first place.
Thanks to the excellent research and presentation by Dr. Reddy and his colleagues before the FDA, I’ll go out on a limb and predict the FDA will approve the Watchman device, probably by the middle of 2015.
The Watchman device closes off the LAA where 90-95% of A-Fib strokes come from. It’s a very low risk procedure that takes as little as 20 minutes to install. Afterward, you would usually not need to be on blood thinners. (For more, see my article, The Watchman Device: The Alternative to Blood Thinners).
If the FDA were to not approve the Watchman, this would be a major setback in the treatment of A-Fib in the US. The Watchman is approved everywhere else in the world. One would have to go to Canada or overseas to get the Watchman installed.
NOTE: Dr. Reddy also discussed this topic in February at the 2015 International Symposium on Left Atrial Appendage (ISLLA) held in Marina Del Rey, CA.
Last updated: Wednesday, April 22, 2015