Wired for vascular health
European scientists have successfully implanted a tiny pacemaker into several patients to control high blood pressure -- and report reductions that surpass what medicines have been able to do for these patients.
“This has tremendous potential,” said Dr. Frank Veith, a professor of surgery at New York University School of Medicine who runs the Veith Symposium, an annual scientific meeting at which the results were reported. “It’s early, but ultimately I think it may work,” Veith said of the new device.
Millions of people have high blood pressure, a major risk factor for heart disease and stroke. According to the American Heart Assn., a blood pressure reading of 120/80 millimeters of mercury, or mm Hg, is considered normal. High blood pressure is a consistent reading of 140/90 mm Hg or higher.
About 10% to 15% of those with high blood pressure are not helped by medicines, even after taking at least three different ones.
That is why Dr. Jurg Schmidli, chief of vascular surgery at the University Hospital Berne in Switzerland, agreed to test an experimental implantable device to lower blood pressure in patients who don’t respond to available medicines.
The idea is not new. Three decades ago, on the heels of the first cardiac pacemaker, surgeons tried to lower blood pressure with a similar pacemaker. The machines were too cumbersome and big, and the technology was abandoned.
But in 2002, using new implantable technology, surgeons tested the device in 11 patients undergoing carotid surgery for stenosis, a narrowing of the main arteries feeding the brain.
Schmidli and colleagues placed electrodes outside the carotid wall and applied electrical stimulation. The result was a swift drop in blood pressure.
Stimulating the carotid sinus sends messages to baroreceptors in the brain that control blood pressure.
The study was expanded into a multicentered trial of 45 patients. So far 31 of 45 patients -- all suffering high blood pressure despite taking an average of five medications each -- have had surgery to place electrodes outside the carotid and to place an internal pulse generator into the chest wall. Schmidli operated on six of these patients.
He reported at the symposium, held earlier this month, that the first 16 patients experienced an average drop of 29 millimeters of mercury. “By comparison, if a drug reduced blood pressure by 9 millimeters it is considered major,” Schmidli said. “It is promising.”
But it is major surgery, and there were some side effects. Initially, some patients complained of a toothache while eating ice cream. (The carotid arteries are in the neck.) The voltage of the stimulation was lowered and the side effect was resolved. Two patients with infections had the device removed.
After two years, ultrasound images of the carotid arteries showed no residual effect of the stimulation. There was no carotid narrowing, which Schmidli said was a major ethical and medical concern because carotid narrowing could lead to a stroke.
