Restricting Blood Flow May Help Heart Bypass Patients
THURSDAY Aug. 16, 2007 -- In a potentially significant discovery for heart bypass patients, British researchers are reporting that limiting blood flow to an arm before surgery produced better results in a small trial of patients.
Restricting blood flow before surgery reduced levels of troponin T, a cardiac protein that is released into the bloodstream after injury to the heart and is associated with poor outcomes after surgery, the researchers said.
"If you remotely precondition the heart before surgery, you get significant protection," said study researcher Dr. Derek Yellon, of University College London's Hatter Cardiovascular Institute. "You can significantly reduce troponin T in patients undergoing bypass surgery."
"Remote preconditioning is a phenomena in which, if one deprives the blood supply to an organ or tissue, other than the heart, that initiates a protective mechanism on the heart," added study lead author Dr. Derek J. Hausenloy, also from the Hatter Cardiovascular Institute.
The findings are published in the Aug. 18 issue of The Lancet.
Heart bypass surgery is done to reroute -- or "bypass" -- blood around clogged arteries to improve blood flow and oxygen to the heart, according to the American Heart Association.
In the trial, the British researchers restricted blood supply to the heart by restricting blood flow in an arm. Yellon and Hausenloy studied 57 patients undergoing coronary artery bypass surgery. Twenty-seven of the patients underwent heart preconditioning -- restrictions of blood flow -- before the operation.
Preconditioning consisted of three, five-minute cycles of restricting blood flow in one arm by inflating a blood pressure cuff that acted like a tourniquet. Between each cycle, the cuff was deflated.
Before and after surgery, the researchers measured the blood levels of troponin T in all patients. They found that levels of the protein were reduced by 43 percent among patients who had undergone preconditioning, compared with those who hadn't.
"If you can have a noninvasive technique that can reduce by 43 percent the amount of injury sustained by the heart during bypass surgery, then you can improve the morbidity and mortality of patients," Hausenloy said.
More study is needed to see if the technique actually improves clinical outcomes, Hausenloy said. "If this can be shown, it may warrant a change in clinical practice in all patients undergoing bypass surgery," he added.
Another heart expert agrees that if this concept is workable, it could represent a major advance in heart-bypass surgery.
"Revascularization, with angioplasty or bypass surgery, carries risk of heart muscle damage, measured in the study by troponin release," said Dr. Henry Purcell, of the Royal Brompton Hospital in London, and co-author of an accompanying editorial in the journal. "We need to minimize these risks in cardiac and non-cardiac surgery."
"We clearly need more data, and the current team is designing outcome studies to see if this protection translates into clinical benefits," Purcell said.
In another report in the same issue of the journal, South Korean researchers showed that use of the painkiller celecoxib (Celebrex) after implanting a stent to open blocked arteries in people with coronary artery disease is safe and might reduce the need for repeat procedures.
Dr Hyo-Soo Kim, of Seoul National University Hospital, and colleagues studied 274 patients, all of whom were given 100 milligrams of aspirin and 75 milligrams of Plavix -- a drug designed to prevent blood clots -- a day. In addition, 136 were randomly assigned to receive celecoxib before and after the procedure.
"These data suggest that the adjunctive use of celecoxib for six months after stent implantation in patients with coronary artery is safe," the researchers wrote.
In addition, they say that unlike another cox-2 inhibitor, Vioxx, celecoxib does not increase the risk of heart attack. "Administration of celecoxib for six months does not seem to increase the risk of adverse cardiac events in the intermediate term when used with dual anti-platelet therapy," they wrote.
However, another accompanying journal editorial warned that clinical trials suggest that long-term use of celecoxib may increase the risk of heart attack.
To learn more about bypass surgery, visit the American Heart Association.
Posted: August 2007
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