The Rheos System includes two small stimulating devices, called "leads," which are implanted, under general anesthesia, next to the carotid sinuses located on the right and left sides of the neck. It also includes a pulse generator that is about the size of a small cell phone, which is implanted in the chest (see picture, below). The generator delivers a pulse of energy between one and 7.5 volts to the leads, which conduct the energy to the carotid baroreceptors. The baroreceptors are then activated, generating nerve impulses that travel to the cardiovascular control centers in the brain, which then slow the heart rate and cause blood vessels to dilate, reducing the amount of pressure the heart must use to pump the blood, and reducing its workload.

Before joining the study, participants must already be on three hypertensive medications including a diuretic which have been shown not to be effective. Dr. Shimbo stresses that any reduction in blood pressure is beneficial in patients with severe refractory hypertension.


"Our hope is that the device will ultimately make a significant difference in patients' lives by effectively lowering their elevated blood pressure levels and possibly extending their lives," Dr. Shimbo says.

Hypertension affects millions of Americans, and a significant proportion of them cannot control their hypertension, despite the use of multiple medications. Every patient in the 300-person randomized double-blinded clinical trial will have the device implanted. In half of the patients it will be turned off for the first six months, and then turned on for another six months. In the other half of patients, it will be turned on for the first six months. The device in these latter patients will be kept on for another six months to determine the long-term effectiveness of the device.

In an earlier feasibility trial, 59 implants were done worldwide with no unanticipated adverse device effects, including device failures, arrhythmias, postural hypotension, or stenosis of the carotid artery.

One study subject is already seeing the difference in a big way. New Jersey resident Tom Pareso volunteered to have a Rheos installed when he reached the end of his rope with four different hypertension medications that left him exhausted and tired most of the day. The 47-year-old mosquito inspector said his job isn't particularly stressful, but that his family has had a history of hypertension.

On Sept. 19, 2008, Pareso had one of the devices implanted by CUMC neurosurgeon E. Sander Connolly, also the study's principal surgical investigator. Dr. Connolly said Pareso was an ideal candidate since his hypertension was particularly stubborn and his symptoms were not alleviated by medication.

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