Implanted Electrical Device Showed Marked Drop in Blood Pressure

BY MITCHEL L. ZOLER

PHILADELPHIA -- Electrical stimulation of the carotid sinus by an implanted device led to substantial drops in blood pressure in a phase II study with 10 patients at five centers in the United States, Dr. Karl A. Illig said at the Vascular Annual Meeting, sponsored by the Society for Vascular Surgery.

A maximum, 6-V dose of continuous electrical stimulation led to a reduction of systolic blood pressure of about 65 mm Hg in patients with drug-resistant hypertension, reported Dr. Illig, chief of the division of vascular surgery at the University of Rochester (N.Y.). On the basis of these results, CVRx Inc., the Minnesota-based company that makes the Rheos system, is working with the Food and Drug Administration to plan a randomized, controlled trial as more phase II patients accrue. Dr.Illig and his associates receive research support from CVRx.

The current form of the stimulator device comprises two electrodes that are placed on the carotid sinus during open surgery. The electrodes are attached to a subcutaneously implanted pulse generator and controlled with an external wand, similar to an implanted pacemaker. Patients in the 2005 U.S. study had an average age of 50 years, and their average blood pressure by an office reading was 175/101 mm Hg, even though they took a mean of six antihypertensive medications.

All showed a dose-response drop in blood pressure as the voltage was increased from zero to the maximum of 6 V. The dose response was maintained throughout 3 months of follow-up. The drop in both systolic and diastolic pressure was achieved with a modest reduction in heart rate, which fell to about 70 beats/min. Patients were asked to maintain their antihypertensive medications after the device was turned on. In this series, there were no adverse effects and there was no morbidity, aside from what would be expected from the surgical incision.

A total of 37 patients have been implanted worldwide, Dr. Illig said. The only adverse effects have been infections in two patients, a number in line with the size of the device (which should get smaller with refinements).