mplanted Device Causes Body to Naturally Lower Blood Pressure
Columbia University Medical Center and NewYork-Presbyterian Hospital
Lead National Trial of New Therapeutic Technology
NEW YORK (Dec. 12, 2008) – High blood pressure can be so taxing on the heart that, unchecked, it will eventually cause an otherwise healthy heart to overwork itself and quit — not to mention spur a host of other difficulties, such as rendering the heart muscle so thick it can look like a liver.
So it’s understandable that many cardiologists, in an effort to get to the root of the myriad health problems that stem from hypertension, have focused on alleviating the condition with drugs. But patients whose extreme hypertension won’t respond to medication or changes in lifestyle may soon have a new option to lower their blood pressure: surgery.
Daichi Shimbo, M.D., leads the Rheos study, which is being conducted out of the Behavioral Cardiovascular Health & Hypertension Program at CUMC.
A multi-center, 300-patient trial led by researchers at Columbia University Medical Center (CUMC) and NewYork-Presbyterian Hospital is testing the efficacy of the Rheos Baroreflex Hypertension Therapy System. The Food and Drug Administration-approved system is implanted surgically, with minimal scarring, under the skin in the neck and electronically stimulates the receptors in the carotid sinus, the area located at the bifurcations of the carotid arteries that are responsible for regulating blood pressure.
“One-third of the world’s population is hypertensive, and only one-third of those people can only control their hypertension with the help of drugs,” says Dr. Daichi Shimbo, assistant professor in the Center for Behavioral Cardiovascular Health at Columbia University Medical Center and the medical principal investigator for the multi-center trial. “There is a vast segment of the hypertensive population that could potentially benefit from surgically intervening to alter the way baroreceptors function.”
Baroreceptors work like a thermostat that automatically turns on the air conditioning when the air temperature becomes too hot. By activating the baroreceptors and sending signals to the brain, the Rheos System causes the brain to perceive a rise in blood pressure. The brain then acts to reduce blood pressure by sending signals to the blood vessels, heart and kidneys, the major organ systems involved in the control of blood pressure.
“The system is designed to work by stimulating the baroreceptors in the carotid sinus to make it appear as if patients are more hypertensive than they really are, forcing the body to respond and lower blood pressure,” said Thomas Pickering, M.D., director of the CUMC Center for Behavioral Cardiovascular Health, and the national principal investigator of the trial. “For patients who have been unsuccessful at lowering extremely high blood pressures with the current pharmacological therapies, this device may be an invaluable option.”
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.
Smaller device, more easily adjusted
E. Sander Connolly Jr., M.D., associate professor of neurological surgery
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.
The Rheos Baroreflex System, seen here beside a carotid sinus model and a quarter, for scale.
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.
Two weeks later Pareso came in for his check-up, and doctors recorded lower readings. The sutures in his neck here barely visible and Pareso said he was feeling fine: “My hope is to eventually get off the meds and get my energy back. After taking Catapres everyday, I would start dozing off. I’m not sleepy now.”
Stimulating the baroreceptors to lower blood pressure is not a new idea, but early attempts at carotid nerve stimulation were bulky and the devices were crude. The most recent device was more easily implanted and the surgery was conducted without incident, Dr. Connolly said.
The FDA-approved device used in this study is the Rheos System made by CVRx, a private, Minneapolis-based company that develops proprietary active implantable technology for the treatment of hypertension. Other centers participating in the trial include Washington University, Boston University Medical Center, University of Rochester and Hackensack University Medical Center.
For more information about the study, or to participate, please visit: http://www.bloodpressuretrial.com/index.html or call 1(888) 8BP-RISK.
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Columbia University Medical Center provides international leadership in basic, pre-clinical and clinical research, in medical and health sciences education, and in patient care. The medical center trains future leaders and includes the dedicated work of many physicians, scientists, public health professionals, dentists, and nurses at the College of Physicians & Surgeons, the Mailman School of Public Health, the College of Dental Medicine, the School of Nursing, the biomedical departments of the Graduate School of Arts and Sciences, and allied research centers and institutions. Established in 1767, Columbia’s College of Physicians & Surgeons was the first institution in the country to grant the M.D. degree and is among the most selective medical schools in the country. Columbia University Medical Center is home to the largest medical research enterprise in New York City and state and one of the largest in the United States. For more information, please visit www.cumc.columbia.edu.
NewYork-Presbyterian Hospital — based in New York City — is the nation’s largest not-for-profit, non-sectarian hospital, with 2,242 beds. It provides state-of-the-art inpatient, ambulatory and preventive care in all areas of medicine at five major centers: NewYork-Presbyterian Hospital/Weill Cornell Medical Center, NewYork-Presbyterian Hospital/Columbia University Medical Center, Morgan Stanley Children’s Hospital of NewYork-Presbyterian, NewYork-Presbyterian Hospital/Allen Pavilion and NewYork-Presbyterian Hospital/Westchester Division. One of the largest and most comprehensive health care institutions in the world, the Hospital is committed to excellence in patient care, research, education and community service. It ranks sixth in U.S.News & World Report’s guide to “America’s Best Hospitals,” ranks first on New York magazine’s “Best Hospitals” survey, has the greatest number of physicians listed in New York magazine’s “Best Doctors” issue, and is included among Solucient’s top 15 major teaching hospitals.
The Hospital is ranked with among the lowest mortality rates for heart attack and heart failure in the country, according to a 2007 U.S. Department of Health and Human Services (HHS) report card. The Hospital has academic affiliations with two of the nation’s leading medical colleges: Weill Cornell Medical College and Columbia University College of Physicians and Surgeons. For more information, visit www.nyp.org.