November 17, 2010

MIT Technology Review

Surgery Dramatically Lowers Blood Pressure

New treatment may be a way to control hypertension when drugs don't work.

A California company has shown how to dramatically lower blood pressure in hard-to-treat patients by destroying tiny nerves in the kidney.

The nerves are located inside the main arteries leading to the kidney. They affect blood pressure by controlling the release of sodium and an enzyme called renin, and by managing blood flow from the kidneys themselves.

The procedure was developed by Ardian, a medical device company based in Mountain View, California. Previous studies have shown that these nerves are overactive in many people with high blood pressure, says Murray Esler, who led the new research. By destroying these nerves in about 50 people, Esler could reduce those patients' uncontrolled high blood pressure by nearly 30 percent. A study describing the work was presented today at the American Heart Association, and the work is published in The Lancet.

Previous research has suggested that high blood pressure dramatically increases the risk of death. But effective medication may only reduce blood pressure up about 10 percent, says Esler, associate director of the Baker IDI Heart and Diabetes Institute, in Melbourne, Australia. This is the first controlled trial to explore the impact that destroying these nerves would have on high blood pressure, Esler says.

About 10 percent of the patients who had the procedure saw little or no benefit. Esler says this compares favorably to a typical drug, which might only have a 50 percent response rate. Patients in both groups continued to take medication during the six-month study, though the dosages were lowered for some of those who had the surgery. None of the patients involved in the trial suffered any significant ill effects.

Doctors slid a catheter into each of a patient's two renal arteries, and blasted the nerves with heat high enough to destroy them but not damage the surrounding arterial wall. Some participants have been followed for more than two-and-a-half years so far, and their blood pressure has remained lower, suggesting the nerves do not grow back and that improvements last long-term, Esler said.

The procedure can be performed in 40 to 60 minutes with an overnight hospital stay, says Andrew Cleland, Ardian's president and CEO. The cost has not been determined yet, but will likely be on the order of $10,000, Cleland says.

The company is awaiting U.S. Food and Drug Administration approval to begin a similar research trial in the United States with 350 patients whose high blood pressure isn't controlled by medication. The company already has permission to do the procedure in Europe, and will begin commercializing it early in 2011, Cleland said.

Future research will also explore the potential benefit of the Symplicity Catheter System on diabetes, after a pilot study suggested that destroying the nerves also improved clinical markers of diabetes.

Randall Zusman, director of the division of hypertension at the Massachusetts General Hospital Heart Center, questions how big the potential market really is. He says only a handful of his 3,000 current patients are as drug-resistant as the patients in Esler's research. "When you make a concerted effort—five drugs or more—you're going to get most people under control," Zusman says.

But both Zusman and Aram Chobanian, a hypertension expert at Boston University, say they were impressed by the size of the drop in blood pressure, and look forward to seeing more research.

"The effects on blood pressure are quite remarkable," says Chobanian. No existing drug has done more to lower blood pressure, he says. "The initial data provided here are very impressive."

Copyright Technology Review 2010.