After six years, three advisory panels, and a highly publicized approval process, Boston Scientific’s Watchman left atrial appendage (LAA) device has been approved for sale in the United States. An alternative to blood thinners and other drug therapies, Watchman presents a novel, interventional approach to stroke management in patients with atrial fibrillation (AF). The technology seals off the LAA, a vestigial structure accountable for up to 90% of all stroke-causing clots.
Rocky road to approval
However, the approval comes after a somewhat Odysseus-like journey through FDA panels. In 2009, a FDA advisory panel voted in favor of approval, but the FDA ultimately issued a letter stating that the device was not approvable and required additional safety data due to the PROTECT-AF trial’s final results showing bleeding and other complications.
Following this setback, a 2013 FDA advisory committee again voted in favor of approval following the early results of the PREVAIL trial; however, the PREVAIL trial’s final results failed on the primary efficacy endpoint. That same PREVAIL trial had its feature presentation pulled from the American College of Cardiology’s annual meeting after Boston Scientific broke the research embargo and distributed a press release summarizing the results of the trial.
Moving forward to this fall, an approval panel in October 2014 re-convened to assess their 2013 approval recommendation and split 6 to 5 in favor of approval with one abstention. The 2014 panel recommended that Watchman receive approval for AF patients who are eligible for, but opt not to take warfarin.
Assessing the eligible patient population
While the PROTECT-AF and PREVAIL trials showed that Watchman is not equivalent to warfarin for reducing ischemic stroke for AF patients, approximately 2.5 million Americans have AF, and a significant proportion of these patients may be candidates for the Watchman LAA.
Four case studies on structural heart disease program development
Under the FDA approval, eligible patients include those with “non-valvular atrial fibrillation who are at increased risk for stroke and systemic embolism based on CHADS2 or CHA2DS2-VASc scores, are deemed by their physicians to be suitable for warfarin; and have an appropriate rationale to seek a non-pharmacologic alternative to warfarin, taking into account the safety and effectiveness of the device compared to warfarin.” (Boston Scientific Press Release, March 13 2015).
Just what the “appropriate rationale” to seek a non-pharmacologic alternative may be is left open to interpretation, leaving some uncertainty about the exact market opportunity for device-based treatment. That said, it’s safe to say a significant proportion of AF patients on warfarin will be interested in alternatives, considering the challenges associated with this drug, including bleeding risk and difficulty maintaining a defined anticoagulation range.
Looking ahead to adoption
With the FDA’s approval, structural heart programs now have a viable alternative for stroke management in AF patients. In considering LAA adoption, we’ve developed four criteria our members should review as part of their structural heart strategic plan.