July 27th, 2011

Mixed Results for New Implantable Device to Treat Resistant Hypertension

A phase III trial has yielded mixed results for an experimental implantable device that uses baroreflex activation therapy (BAT) to treat resistant hypertension. The article on the manufacturer-funded Rheos Pivotal Trial, by John Bisognano and colleagues, has been published online in the Journal of the American College of Cardiology.

The Rheos device was implanted in 265 patients with resistant hypertension. After 1 month, they were then randomized, on a 2:1 basis, to have the device activated immediately (Group A) or after 6 months (Group B). There were 5 coprimary endpoints. The trial demonstrated sustained efficacy, BAT safety, and device safety, but endpoints for acute systolic blood pressure (SBP) response and procedural safety were not met successfully:

  1. The acute SBP responder rate at 6 months was 54% for group A versus 46% in Group B (P=0.97), short of the 20% superiority margin.
  2. The sustained responder rate at 12 months, 88% (P<0.001), met predefined criteria.
  3. Procedural safety: The procedure-related event-free rate of 74.8% did not meet the prespecified performance criterion of 82%.
  4. BAT safety: The therapy-related event-free rate between 30 days and 6 months was 91.7% in Group A and 89.3% in Group B (P<0.001), which was within the noninferiority margin.
  5. Device safety: The event-free rate of 87.2% exceeded the prespecified performance criterion of 72%.

In their discussion, the authors acknowledge that the trial failed to meet all its endpoints but point out that the device produced significant reductions in SBP at 12 months and that more than half of the subjects reached a SBP of 140 mm Hg or lower. They write that the manufacturer has developed a less invasive implant procedure for delivering BAT; it will be tested in future trials.

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