Renal Denervation Study to Begin on Patients with Uncontrolled Hypertension

Michael Wilensky, MD
Medtronic is sponsoring a national study that will assess a minimally invasive endovascular treatment for uncontrolled hypertension. “We’ve just done our first three cases,” says Michael Wilensky, MD, with Cardiology PC, one of the 60 study sites.


The study, now in the recruiting phase in the U.S., entails denervating renal arteries. The European portion of the study recently finished with strong success. “It showed significant reduction in hypertension and got patients off some, if not all, their drugs,” Wilensky says.


Eligible subjects must be adults on at least three hypertension drugs at the highest tolerated dosage and a minimum systolic blood pressure of 160 mmHg. The study aims to enroll 1,060 patients and follow them over three years.


“If we treat twenty candidates from our practice, that would be a lot because you have to have a really compliant patient,” Wilensky says. Patients must journal daily, wear a 24-hour blood pressure monitor, and be able to articulate accurately on their status in an array of areas.


“It’s not the easiest enrollment we’ve ever had. For other studies, we might find two or three candidates a day in the cath lab,” Wilensky says. He estimates it may take a year to find enough candidates nationally.


The Symplicity Catheter System study seeks to take advantage of the elusive relationship between the renal nerve and the brain. “We know there’s a feedback loop that causes hormones that raise blood pressure. We may not know all the specifics, but it has been hypothesized that when you cut off that feedback loop, you see a substantial drop in blood pressure,” Wilensky says.



The study’s technique for destroying a portion of the renal nerves emulates the one employed by cardiologists to ablate areas of the heart showing signs of arrhythmia. “The idea of destroying tissue with radio frequency energy (RFE) is not a new concept; using it to treat hypertension is the novel part,” Wilensky says.


The endovascular procedure mirrors an arteriogram of the kidney or the leg. Using the femoral access through the groin, the cardiologist visually verifies the catheter’s position in the renal artery and then runs the RFE device through the catheter so direct contact can be made to the nerves housed in the renal artery wall.


Then the machine hooked to the catheter guides the cardiologist on where and when to apply the RFE. “You make sure you’re in a good position, then step on the pedal to make the burn, rotate the catheter, make the burn, and repeat until the entire circumference in that position has been covered. Then you move to the next position. You do that in both renal arteries,” Wilensky says.


The study incorporates a control arm where a small number of patients initially undergo a sham denervation procedure. At the six-month timepoint, however, these patients become eligible for the active procedure.


In the European study, “a huge portion of the candidates lowered their blood pressure,” Wilensky says. The average drop was 32 points systolic and 10 diastolic. 84 percent saw at least a 10-point reduction compared to only 35 percent of those on medications only. The study, published in the January 2010 issue of The Lancet, utilized 106 patients.


“We need to proceed carefully with this, even though it’s a great idea, because if this is found to damage the artery as well, it would be a danger,” Wilensky says. At their six-month follow-up visit, patients will receive a renal ultrasound to evaluate both renal arteries.


Wilensky says this treatment option would suit the cardiology field well. “Since we’re interventional by nature, doing a procedure rather than medications — especially where the meds aren’t working — is attractive,” he says. “If this procedure works, then patients with resistant hypertension would be admitted one morning, have a one-hour procedure, and possibly go home that day with a reduced pill burden.”


Cardiology PC expects to begin two more novel studies soon. One involves assessing a bio-absorbable stent. Because this new material, unlike metal, would allow the vessel to return to its more natural state, it would not adversely affect blood flow dynamics or raise the risks of clotting related to the stent procedure.


Another study employs stem cells to correct damaged heart tissue. The candidates would be patients with significant chest pain from lack of blood flow to parts of their heart with no other treatment options. The study uses a medication to stimulate the bone marrow to release stem cells into the circulatory system. “Then we harvest the stem cells and inject the CD34+ cells into the damaged areas where we need them,” Wilensky says. “Hopefully these new cells would heal the damaged tissue and bring new blood flow to the area, relieving the patient’s angina.”




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