According to the Centers for Disease Control and Prevention, more than 30 percent of American adults have high blood pressure, a major risk factor for heart attack and stroke. The standard treatment is medication, but some patients are unable to control their high blood pressure despite taking three or more medications.
A team of University of Virginia School of Medicine physicians is studying whether a surgical procedure can reduce blood pressure. The treatment, called renal denervation, removes nerves in the kidney.
"A non-medical treatment would be welcomed for many patients with difficult-to-control blood pressures who are resistant to typical blood pressure medications," said cardiologist Dr. Dearing Johns, a specialist in treating high blood pressure who will help evaluate trial participants.
U.Va. is the only center in Virginia participating in this clinical trial; currently, renal denervation is available only through the trial. Trial participants are randomized to receive either renal denervation or continue on their medications. After six months, participants who are randomly chosen to continue on their medications have the opportunity to receive renal denervation.
The nerves are part of the body's sympathetic nervous system, which triggers what is commonly called the "fight or flight" response in humans under stress, Angle said. Increases in sympathetic nerve activity have been shown to make high blood pressure worse. Experimental models and surgical experience have shown that removing these nerves can help control blood pressure, Angle said; however, the surgery is considered too invasive.
Renal denervation uses a minimally invasive approach to removing the sympathetic nerves. As part of a renal angiogram – which takes X-rays of the blood vessels to the kidneys – a small catheter is inserted into an artery at the patient's groin and advanced to the main kidney arteries. Radiofrequency energy is then employed to destroy the kidney's sympathetic nerves.
"If we can destroy the sympathetic nerves to the kidneys, we break a cycle of nerve signals that raise blood pressure," Angle said.
The heat from the radiofrequency energy is low enough that it only impacts the sympathetic nerves and not the artery wall or any healthy surrounding tissue. "The blood flow acts like a radiator to protect the artery wall," Angle said.
The procedure typically takes about an hour. Trial participants are awake during the procedure but receive medication to help them feel comfortable. After the procedure, trial participants are observed overnight in the hospital, with follow-up continuing for three years.
"Previous clinical trials from Europe suggest the results from this procedure are excellent and durable in helping to control high blood pressure," Angle said. "We are doing this trial to figure out the long-term results and determine which patients are the best fit. We are excited about this potentially ground-breaking technology for a very common problem."