Simple device helps cut heart attack severity
CTV.ca News Staff
Published Friday, February 26, 2010 10:04AM EST
Something as simple as a blood pressure cuff – commonly found in any ambulance or doctor's office -- can help reduce the severity of heart attacks by as much as 50 per cent, new Canadian research has found.
Researchers led by Dr. Andrew Redington, a cardiologist at the Hospital for Sick Children in Toronto, have found that intermittently inflating the cuff on the arm of someone having a heart attack helps set off a response that lessens the heart damage caused by the attack.
The low-cost method is called remote ischemic preconditioning. While it's not a new idea, Redington and a team working with Dr. Rajesh Kharbanda from the U.K., are the first to investigate how it can help adult patients having a heart attack.
It's not clear how ischemic preconditioning works precisely, but it's thought that when the cuff cuts off circulation to the limb, the reduced blood and oxygen flow sends a warning message to the body. That triggers the release of little-understood substances in the blood that somehow protect the body and heart from subsequent injury.
"This technique releases a substance into the blood that bathes all the tissues and protects all of the tissues," Reddington told CTV News Thursday.
"It's probably the most powerful natural protective mechanism that we know about and it is a way for the cells to protect themselves from having reduced blood oxygen or reduced blood flow."
He explained that preconditioning is something that's been studied for about 25 years, having been first tested in animals.
Reddington studied the phenomenon in 2006, when he showed that ischemic preconditioning helps to reduce heart damage in children undergoing heart surgery. Others have shown the effect in adults undergoing cardiac and vascular surgery, as well as coronary angioplasty.
But this is the first study to examine it in adults having a heart attack.
For the study, researchers looked at more than 250 Danish adult patients, who were having heart attacks. Half the patients received remote ischemic preconditioning in the ambulance on the way to the hospital.
The ambulance attendant used a blood pressure cuff to cut off blood flow to the arm for five minutes, then deflate it for five minutes, four times.
When the patients arrived at hospital, they received regular heart attack treatment including angioplasty (a procedure to mechanically open narrowed or blocked blood vessels to the heart).
The researchers found that compared to the control group, the size of the heart attack was reduced by about 30 per cent overall in patients who were preconditioned. In patients having the largest heart attacks, the size was reduced by about 50 per cent.
Redington says the results, published in the Feb. 26 edition of The Lancet, were impressive.
"It was a massive reduction in the amount of damage done to the heart by using this simple technique," he said.
He notes that the smaller the amount of heart tissue that's damaged in an attack, the more likely the patient is to survive.
"The larger the heart attack, the more heart muscle that dies, obviously, the worse the outcome," he said.
Redington his team are now working on developing an automated cuff that would make providing preconditioning easier and more efficient for health-care workers. SickKids has licensed intellectual property and is working with a Canadian company to develop the product.
The next step is to test the cuff in different kinds of patients, such as those having a stroke. His team also wants to know whether the technique not just reduces the severity of the heart, but leads to improved survival rates, patient well-being and quality of life.
"It's being studied in multiple clinical scenarios so it has potential benefit in children in adults undergoing general as well as cardiac surgery," Redington said.