Science

Heart damage curbed with blood pressure cuff

Using a blood pressure cuff to intermittently stop blood flow in the arm helps reduce the amount of damage from a heart attack, researchers say.

Virtually everyone has had their blood pressure measured with a pumped-up cuff encircling their upper arm.

But it turns out that this commonplace medical device could one day have another critical use — reducing the amount of damage from a heart attack, researchers say.

In a study of more than 250 Danish adults experiencing a heart attack, Canadian-led scientists used a blood pressure cuff to intermittently stop blood flow in the arm, a process that begins while a patient is being transported to hospital by ambulance. 

'Any reduction in heart attack size is beneficial and a 50 per cent reduction is really quite remarkable.'— Dr. Andrew Redington

Called "remote ischemic preconditioning," the procedure developed by Toronto's Hospital for Sick Children was found to significantly limit the amount of damage to the heart muscle caused by a blockage in a cardiac blood vessel.

Ischemic preconditioning involves using the device to interrupt blood flow in the arm, off and on over a period of 35 to 40 minutes: the cuff is inflated for five minutes, then deflated for five minutes, with the procedure being repeated consecutively four times.

Once at the hospital, the patient receives routine heart attack treatment, including cardiac angioplasty. Preconditioning using the cuff may still be going on throughout this procedure, which uses a tiny inflatable balloon to open up narrowed or blocked blood vessels to the heart.

Researchers, whose paper appears in Friday's issue of The Lancet, found that those heart attack patients randomly assigned to have preconditioning had an overall reduction in heart muscle damage of 30 per cent, compared to those not treated with the cuff.

In those having the largest, typically most devastating, heart attacks, the amount of damage was cut by about 50 per cent, said senior co-author Dr. Andrew Redington, head of cardiology at Sick Kids Hospital.

"And we know, of course, that the bigger the heart attack you have, the more likely you are to die and the more likely you are to have subsequent symptoms of heart failure and all the bad things that having a heart attack predicts," Redington said in an interview Thursday. "So any reduction in heart attack size is beneficial and a 50 per cent reduction is really quite remarkable."

Redington, who co-ordinated the joint study by researchers in Toronto, Denmark and England, said the idea of ischemic preconditioning first arose about 25 years ago, primarily because of work in laboratory animals.

Scientists found that if tissues are starved of blood in an intermittent manner, it seems to prepare them for a more prolonged interruption in blood and oxygen supply, he said, explaining that halting flow releases a substance into the blood that "circulates and bathes all the organs, not just the heart, to protect them."

Pay off for patients unknown

In the first human study, performed at Sick Kids Hospital and reported in 2006, Redington showed that preconditioning also helps to reduce heart damage in children undergoing open-heart surgery. Others have since shown the same effect in adults having cardiac and vascular surgery.

In his study on children, Redington said it wasn't just the heart that was protected from damage during surgery. "We had evidence that the lungs were better and the amount of inflammation in the body was reduced as a result of preconditioning."

While he calls the results exciting, Redington cautioned that much more research is needed before the technique could become part of everyday medical practice.

"This is the first study showing its effects in heart attacks," he said. "What I would like to see now is this being expanded to a much broader and larger group of patients so that we could look at some things … Does it improve death rates? Does it improve great failure rates? Does it reduce subsequent hospital admissions?"

"Therefore, does the patient get a tangible benefit?"

Dr. Robert Welsh, director of the interventional cardiology program at the University of Alberta, said the idea of cutting off blood supply a distance away from the heart to reduce cell death in the organ is "quite a neat concept."

"Obviously before something like this gets implemented, people would want a much more definitive study, because these [patient] numbers are really quite small," Welsh, who was not involved in the study, said from Edmonton.

"People are going to want to see a study of 2,000 people, which really is a key opportunity for Canadian centres because we have good collaborative networks for the treatment of heart attack," he said, noting that his program had been planning a similar study and would be interested in a joint research project.

Simple, safe and cheap

In an accompanying commentary, Drs. Michel Ovize and Eric Bonnefoy of Lyon, France, say the technique might represent a "powerful new treatment option."

"At a time of major difficulties in supporting the cost of our health-care systems, [the researchers] have shown that a non-invasive, simple, safe and cheap intervention, possibly done by a paramedic before hospital admission, can significantly increase myocardial salvage."

"Any enthusiasm arising from this encouraging study must, however, be tempered by the need to show actual clinical benefit in larger-scale clinical studies," they write.

Redington's team is also developing an automated cuff that would make it easier and more efficient for health-care workers to use. Sick Kids, which owns the intellectual property rights, is working with a Canadian company to develop the product.

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