For people with high blood pressure that medication can’t control, a new implantable device shows promise, researchers report. The device, surgically placed just below the collarbone, sends a four- to six-volt electrical jolt to the carotid arteries. This is said to lower blood pressure through a process known as baroreflex activation therapy. The device might help tackle a growing problem, said the lead author of the study, which was funded by CVRx Inc., the device’s maker. “We are seeing more patients with resistant hypertension these days,” noted Dr. John D. Bisognano, who is a consultant for CVRx Inc. and a professor of medicine in the division of cardiology at the University of Rochester. “There are a lot of heavier people. There are a lot of diabetic people. We are also realizing that the available drug treatment can’t solve the problem for everybody.”