April 6th, 2011

Getting “Under the Skin” of Resistant Hypertension

Several Cardiology Fellows who are attending ACC.11 this week are blogging together on CardioExchange. The Fellows include Sandeep Mangalmurti, Hansie Mathelier, John Ryan (moderating and providing an outsider’s view from Chicago), Amit Shah, and Justin Vader. See the previous post in this series, and check back often to learn about the biggest buzz in New Orleans.

Treatment-resistant high blood pressure — what to do? It can be frustrating for both patients and clinicians alike, but perhaps there is hope. Today I learned about a cutting-edge treatment in the pipeline: Baroreceptor Activation Therapy, or BAT (see a recent open-access review here). It was discussed as part of the Rheos Pivotal Trial.

Similar to pacemakers and defibrillators, patients with resistant hypertension may eventually have the opportunity to implant this BAT device (the size of a first-generation iPod) under their right clavicle. It works by modulating the autonomic nervous system through baroreceptor reflex stimulation. It may also have downstream vascular and volume effects…

In the trial, which was a multicenter randomized trial of 322 patients, the efficacy and safety of this therapy was evaluated over the course of 1 year. I thought the findings were very interesting and thought-provoking. Some key points:

  • With therapy, approximately 50% of patients achieved the goal of BP <140/90; LV mass index also decreased about 15%
  • About a quarter of patients experienced a side effect related to the surgery (performed by a vascular surgeon). Of these, about a quarter were not reversible (e.g., permanent nerve damage)
  • Even when the device was initially implanted, but not actually turned on, over 40% patients improved and nearly a quarter reached goal blood pressure by six months

The technology is improving as better, smaller devices are developed, and I’m sure complications will eventually drop; nonetheless, any type of surgery is daunting and has potentially fatal risks. All the same, so is the prospect of having a blood pressure of 180/100 despite five medications!

Other complementary therapies also take advantage of the baroreceptor reflex to lower blood pressure, such as acupuncture and yoga. Some holistic practitioners that I know recommend (and swear by) headstands for antihypertensive treatment. Of course, one may break his/her neck in the process! Needless to say, we have much to learn, and the investigation of BAT may provide some valuable insight into the pathophysiology of resistant hypertension, even if it ultimately does not become mainstream.

The limitations and surprising findings raise questions. Were the “resistant” patients actually taking all 3 to 7 medications they were prescribed? Nonadherence is a common reason for “resistant” hypertension. Were the patients (especially those who did not respond to therapy) ruled out for secondary and treatable causes?  How did so many people benefit in the arm where the device was implanted, but not turned on? Ultimately, what is the future of such a therapy? Could make for a good discussion; feel free to share your thoughts!

For more of our ACC.11 coverage of late-breaking clinical trials, interviews with the authors of the most important research, and blogs from our fellows on the most interesting presentations at the meeting, check out our Coverage Roundup.

One Response to “Getting “Under the Skin” of Resistant Hypertension”

  1. Great summary Amit. Thanks for the analysis.