Dive Brief:

• Two long-term studies of FDA-mandated registries have linked Boston Scientific's left atrial appendage closure device, called Watchman, to significant reductions in stroke risk.

• In a paper posted in the Journal of the American College of Cardiology Monday, researchers presented data on more than 1,100 nonvalvular atrial fibrillation patients who were tracked for around 50 months on average.

• The authors described the rate of hemorrhagic stroke seen in the registries as the lowest identified in the nonvalvular afib population,​ strengthening the case for left atrial appendage closure (LAAC).

Dive Insight:

Boston Scientific won FDA approval for its Watchman LAAC device in 2015 on the strength of data from two clinical trials. The trials found the device as good as warfarin at preventing stroke and systemic embolism. Patients who received Watchman had a lower rate of intracranial hemorrhage. 

Surgeons have now implanted Watchman in more than 100,000 patients worldwide. However, while some physicians have embraced the device as a good option for patients who cannot take or comply with anticoagulant regimens, there remain skeptics who point to periprocedural complications and questions about the designs of the clinical trials and argue more evidence is needed.

The registry studies may provide some, but not all, of the evidence required to win over skeptics. In a higher risk population than was enrolled in the earlier trials, the registries linked Watchman to rates of complications below those seen in the randomized trials.

In terms of efficacy, the rates of hemorrhagic stroke were 0.17 and 0.09 per 100 patient years in the two registries. The rates of ischemic stroke were a little higher at 1.30 and 2.20. When compared to the predicted stroke rate, the results suggest Watchman drives between a 69% and 78% reduction in the risk of the cardiovascular event.

The authors of the study concluded the data "adds to increasing information that local site therapy is an effective and safe alternative to long-term anticoagulation." However, an accompanying editorial suggests more evidence will be needed to win over some cardiologists.

John Camm, a cardiologist at St George's University Hospitals in the U.K., wrote that the authors of clinical guidelines are likely to remain cautious about recommending LAAC as an alternative to oral anticoagulation. Camm thinks head-to-head trials against oral anticoagulants are needed, although he acknowledges LAAC is "well worthwhile" for patients unable to take the pharmacological route.  

The data may deliver a boost to an important part of Boston Scientific's structural heart business. In October, Boston Scientific predicted sales at its structural heart unit would approach $725 million for the full year, the top end of its guidance range, as a result of demand for Watchman and three other products. Management said Watchman sales are growing ahead of their plan for the product.

Watchman is the only LAAC device approved in the U.S. but in Europe it faces competition from products including Abbott's Amplatzer. Still, Boston Scientific singled out Europe as a region in which it is seeing "strong demand."