Medtronic on Monday reported positive one-year results of its worldwide clinical trial for renal denervation, a treatment for medication-resistant high blood pressure.

Medtronic’s Symplicity HTN-2 trial showed that patients who received the treatment maintained a significant drop in blood pressure a year after having the procedure, Medtronic reported. In addition, 35 patients who were in the control group of the study – those who had been treated with medication only for the first six months – had denervation after that and showed a drop in blood pressure.

There were no device-related serious problems, no late complications and no significant decline in kidney function after 12 months, Medtronic said.

Study results were published online in Circulation, the Journal of the American Heart Association. Symplicity is not yet approved by the U.S. Food and Drug Administration for sale in the United States. A total of 106 patients at 24 centers around the world are participating in the HTN-2 trial, with half receiving renal denervation in addition to medication and half receiving medication only. After the first six months of the trial, patients on medication only also were offered denervation.

The therapy involves using radio frequency energy to burn spots on the nerves in the wall of the renal arteries. Those nerves are part of the sympathetic nervous system, which affects the major organs responsible for regulating blood pressure – the brain, heart, kidneys and blood vessels. It is a one-time treatment and does not require that a device be implanted.

Treatment-resistant hypertension is persistently high blood pressure despite a patient taking three or more blood pressure medications. An estimated 120 million people worldwide have this problem, putting them at risk for kidney disease, stroke, heart attack and heart failure.

The Symplicity system was launched in April 2010 and is available in parts of Europe, Asia, Africa, Australia and the Americas. It has been used to treat thousands of patients with treatment-resistant hypertension worldwide, Medtronic said Monday.

The FDA granted Medtronic approval for the protocol for SYMPLICITY HTN-3, the company's U.S. clinical trial of Symplicity in August 2011. More information about HTN-3 can be found at