TopTen-HBPai-02Editor’s note: This is the fourth in a 10-part series detailing the top scientific research of 2014, as determined by the American Heart Association’s volunteer and staff leaders.

Despite showing early promise for high blood pressure patients who don’t respond to multiple medications, a medical procedure called renal denervation was no better than a sham procedure, according to a trial published this year.

Renal denervation uses radiofrequency waves to “zap” the nerves surrounding the renal arteries thought to contribute to high blood pressure. The renal arteries supply blood to the kidneys.

The finding appears to contradict earlier studies showing that renal denervation resulted in large drops in blood pressure, leading to its adoption in more than 80 countries. It remains an experimental treatment in the United States.

“I think that it really highlights the importance of appropriate sham-controlled studies and evaluations of medical procedures or new devices,” said Deepak Bhatt, M.D. lead study author and Professor of Medicine, Harvard Medical School and Executive Director of Interventional Cardiovascular Programs at Brigham and Women’s Hospital Heart & Vascular Center in Massachusetts.

The research results are among the top scientific cardiovascular developments in 2014, as determined by the American Heart Association.

In the study, 364 patients with out-of-control blood pressure despite optimal medical therapy received renal denervation, and 171 received a sham, or “fake” procedure. Patients were taking the maximum doses of at least three medications for their blood pressure, including a diuretic.

Researchers measured changes in blood pressure over six months. Systolic blood pressure dropped 14.1 mm Hg in the renal denervation group and 11.7 mm Hg in the sham group, although the difference was not enough to be statistically significant.

These differences were less when patients in both groups measured their blood pressure over 24 hours.

Despite the negative finding, researchers say the study highlights the importance of thorough testing of procedures and devices.

“I think that the implications of the study are really quite profound and go beyond the narrow potential applications of renal denervation for resistant hypertension,” said Bhatt, who also is a spokesman for the American Heart Association.

“The prior studies were not sham-controlled and I think that accounts for at least part of why they were positive and our study was negative,” Bhatt said. “I’m not saying that every single question in medicine needs to be answered with a sham-controlled study — it’s not always going to be feasible and ethical — but when it is feasible and when it is ethical, we should do it.”

People in both study groups significantly reduced their blood pressure after six months, which Bhatt attributes to participants doing better at taking their medication as prescribed. Everyone in the study was required to keep a daily medication diary.

Despite its ineffectiveness, renal denervation was extremely safe, Bhatt said. Other techniques may improve the procedure, but their safety and effectiveness will need to be studied first, he added.

“This is something we learned in drug trials decades ago,” Bhatt said. “That is if one doesn’t do placebo-controlled trials there are all sorts of unintentional and in fact, even well-intentioned biases that can creep into studies.”

Read other top 2014 research: Top Cardiovascular Disease Research Advances of 2014 Summary