Nurses are helping to evaluate a new device that controls blood pressure by stimulating the body’s natural regulatory system.
The device performs like a pacemaker for blood pressure, says Mary Ann Caravaglia, RN, BSN, CCRC, study coordinator at Hackensack University Medical Center (HUMC), Hackensack, N.J.
Surgeons at Hackensack investigating the CVRx Rheos Baroreflex Hypertension Therapy System as part of the multicenter phase 3 Rheos Pivotal Trial have implanted devices in two patients since starting the trial last year. “My first patient is responding well,” Caravaglia says. “We’ve been able to cut down on some of his medications.”
The second patient’s device has not been activated yet.
Other Trial Results
In 2006, a European clinical trial with 12 patients found participants’ systolic blood pressure decreased by 24 mmHg and they experienced no serious adverse events with active Rheos therapy.
After two years, researchers reported 12 of 16 patients experienced at least a 20 mmHg drop in systolic blood pressure on Rheos therapy and five of 16 achieved a systolic blood pressure of less than 140 mmHg.
In 2008, another European study found that baroreflex therapy significantly decreased blood pressure, and researchers noted a trend toward lowering effective renal plasma flow. Investigators concluded Rheos therapy does not impair renal function.
Combined U.S. and European data indicates the overall mass of the left ventricle decreased in 15 of 16 patients who received Rheos therapy. Regression of left ventricular hypertrophy reduces risk of myocardial infarction, sudden death, and heart failure in hypertensive patients.
This early data suggests baroreceptor stimulation may offer patients hope of avoiding hypertensive complications, such as dialysis or congestive heart failure.
“This could be a lifesaver, along with medication,” Caravaglia says. “Nurses should be excited.”
How the Device Works
“The device is designed to work by activating the body’s natural regulation,” says Alecia Harris, a clinical research coordinator at Henry Ford Hospital in Detroit. The Rheos device provides a vibration to the baroreceptors in the walls of the carotid arteries in the neck. Normally, the baroreceptors report to the brain when blood pressure is higher than needed, and the brain sends signals to the body to take steps that will decrease the pressure.
“The leads are wrapped around the carotid,” Caravaglia says. “It stimulates the baroreflex system, which tells the brain to do what it is supposed to do talk to the kidneys, the heart, and vessels to dilate. The kidneys will release fluid and, like a cycle, will lower the blood pressure.”
Kerry Patterson, RN, a clinical research nurse at Rex Hospital in Raleigh, N.C., adds, “It’s like holding a match under a thermostat. Even though the room temperature is 70 degrees and everything is cool, if you hold the match under an old-time thermostat, it will sense it’s hotter than it is, and the air conditioning will kick on.”
That comes in handy when the baroreceptors no longer recognize a person’s blood pressure as being high and fail to send the proper signals to the brain.
CVRx aims to recruit 300 people with hypertension whose disease is not controlled with medication. Patients must be taking and be compliant with three antihypertensives, including a diuretic.
The trial aims to demonstrate a clinically significant reduction in systolic blood pressure at six months and a sustained response to therapy over 12 months, with no serious adverse events.
Before undergoing the procedure, the participant receives a carotid ultrasound to assess whether the bilateral carotid bifurcations are easily identified and below the level of the mandible. Patients with ulcerative plaque in the carotid artery, significant bradyarrhythmias, chronic atrial fibrillation, past surgery or radiation to the carotid sinus region, or organ transplants are excluded. Patients also must have normal kidney function.
The surgeon makes three incisions: one near the collarbone in which the pulse generator is placed, and two above the left and right carotid arteries. This is done in order to attach the Rheos Carotid Sinus Leads around each baroreceptor site. These baroreceptors are located in the carotid sinuses. Any drug that affects the function of the baroreceptors, such as Clonidine, cannot be used, says Caravaglia.
“We need them to respond when we are doing the mapping in the OR,” Caravaglia says.
Once the surgeon locates the most sensitive spots on the left and right, the leads are sutured in place. The surgery takes two to three hours. The patient generally spends two nights in the hospital for observation and incisional wound care. A central line stays in overnight, and the research team tests the voltage parameters of the device while observing the patient’s blood pressure and heart rate on the right, left, and together while programming the device to the minimum through maximum voltage.
The device is turned off and on and voltage adjusted externally. It must remain off for about a month to give the tissue time to heal and the swelling time to subside. After that time, patients return and are blindly randomized at a 2-1 ratio to either have the device turned on or not during the first six months. The physician and the patient do not know whether the device is on or off. Only the programmer knows that information. Then all patients have the device activated. Patients may report tingling or shock-like sensations as the programmer adjusts the device.
Researchers will monitor participants’ blood pressure and heart rate regularly for a year. Medication changes are made, depending on the patient’s response. “It’s a very gentle process, case by case, depending on the response of the patient,” Caravaglia says.