"This is a promising procedure that could revolutionize the way we treat heart attacks," said David Lee, MD, a Stanford interventional cardiologist. "I have great hope that therapeutic cooling can preserve heart muscle and significantly improve a patient's long-term prospects."
Stanford is one of the only medical centers in California participating in a randomized, multi-site clinical study of the cooling technique. The technique involves inducing hypothermia - or subnormal body temperature - in heart-attack patients to protect cells that can become damaged during an attack.
"Cooling is not a novel idea," Lee said, noting that heart surgeons often induce hypothermia during procedures.
During a heart attack, blood flow is significantly reduced or stopped in the arteries - depriving the heart of oxygen and causing irreversible damage to the heart muscle. A physician's goal is to prevent or minimize this damage, and Lee said researchers have long known that cooling has protective qualities. Researchers believe cold temperatures preserve and protect cells when the heart's oxygen supply is cut off, he said, adding that hypothermia may also decrease the release of toxic substances.
"It's an attractive concept - you can cool a patient down and lower the metabolism of the cells," Lee said.
The study involves using the cooling therapy on heart-attack patients who are treated with angioplasty - a procedure to open the blocked blood vessels of the heart. To initiate cooling, which is done within 30 minutes of a heart-attack patient's arrival at the hospital, physicians place a small catheter into a vein in the patient's leg. The catheter is connected to a specially designed device, which induces mild cooling to 91.4 degrees F, more than 7 degrees cooler than normal body temperature. "Basically, we're stealing heat from the body and sending it to a machine," Lee said.
Patients are cooled for three hours, given medication to prevent the normal human shivering response to being cold, and are then slowly warmed. Previous studies have demonstrated that this process helps protect heart tissue, and Lee said cooling is likely to be most effective when initiated early - before permanent heart muscle damage occurs.
The 25-center study, which will involve more than 400 patients, is sponsored by Radiant Medical in Redwood City.
In a separate study reported last year, Stanford researchers used another cooling device to treat stroke patients. Researchers led by Gary Steinberg, MD, PhD, professor and chair of neurosurgery, found that cooling the brain was successful at preventing stroke damage even when done as much as two hours after the beginning of a stroke.
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