Boston Scientific's TAVR safety net device misses study endpoint in reducing number of strokes

A randomized trial of Boston Scientific’s netlike Sentinel device—a miniature strainer designed to catch floating debris in the bloodstream before it can lodge itself within the brain and cause a stroke—failed to meet its primary endpoint as a protective barrier during heart procedures.

In a transcatheter aortic valve replacement (TAVR), where an implant is snaked through the blood vessels and positioned within the heart in a minimally invasive procedure, there is a small chance that damaging debris such as calcium deposits or tissue can be knocked loose during the operation and carried away by the body’s arteries. The company has estimated that about 4% of patients experience a stroke within 30 days of a TAVR procedure.

Placed across the carotid arteries leading the brain, the Sentinel device’s two filters aim to intercept that debris. It received an FDA clearance in 2017 under its previous developer, Claret Medical, which was acquired by Boston Scientific a year later in a $270 million deal.

A registry analysis by the Society of Thoracic Surgeons and the American College of Cardiology showed that since its approval, about 13% of TAVR procedures have included the use of such a device. Boston Scientific, meanwhile, said Sentinel has been used in 75,000 patients.

The latest study—presented at the Cardiovascular Research Foundation’s Transcatheter Cardiovascular Therapeutics conference, known as TCT—represented the largest randomized TAVR trial to date, according to Boston Scientific, by enrolling 3,000 patients at more than 50 global sites and spanning all surgical risk levels.

The Sentinel device came in under the study’s main goals, demonstrating “a non-significant trend towards a lower rate of stroke” among treated patients, the company said, with a rate of 2.3% of all types of strokes compared to 2.9% with the TAVR procedure alone. 

That amounted to a 21% relative risk reduction in the 72 hours after the procedure or by the time of the patient’s discharge from the hospital, whichever came first. There was also no substantial difference between the two groups in the percentage of patients who died, at 0.5% and 0.3%.

However, a secondary analysis showed the device performed better at reducing the number of more severe, disabling strokes during the same time period—0.5% with Sentinel versus 1.3% in the control group, for a statistically significant 60% relative risk reduction.

“Considering strokes are unpredictable, can occur regardless of an individual's clinical background and often take a great toll on a patient's quality-of-life and financial stability, we believe the data appear to demonstrate a consistent effect from [cerebral embolic protection] technology across all patient populations in the trial—supporting the use of the Sentinel device as an effective therapy to reduce the risk of the most debilitating form of stroke for patients undergoing TAVR,” Ian Meredith, Ph.D., Boston Scientific’s global chief medical officer, said in a release. 

The reduction in disabling stroke was consistent across patient subgroups including age, gender, risk, valve type and history of cardiovascular disease. At the same time, the company said the rate of vascular complications from adding Sentinel to a TAVR procedure were low, with only one case of major bleeding, or 0.1% of those enrolled.

The study was also published in The New England Journal of Medicine, with investigators saying that the results may not rule out the benefits of using a Sentinel-like device during TAVR. Boston Scientific said it plans to continue studying the device in a similar trial that is currently enrolling up to 8,000 patients in the U.K.