Action Points
- Explain to interested patients that previous research has found that depriving parts of the body of blood flow for brief periods can protect them, and perhaps other parts of the body as well, against tissue damage from longer and more severe ischemia.
- Explain that the method used in this study needs to be tested in larger trials and with more clinically relevant outcomes before it can be recommended for use outside a clinical trial setting.
Heart attack patients who had an ordinary blood-pressure cuff applied to their arms by paramedics suffered significantly less damage to their heart muscles in a randomized trial than heart attack victims who received standard care.
The finding, reported in the Feb. 27 issue of The Lancet, could represent a payoff from 25 years of research into a phenomenon called ischemic preconditioning.
In a study of 142 evaluable patients, those receiving the cuff treatment plus standard care had a median cardiac salvage index of 0.75 one month later, compared with 0.55 in those receiving standard care alone (P=0.033), according to Hans Erik Bøtker, MD, PhD, of Aarhus University Hospital in Denmark, and colleagues.
Research involving cell cultures and animal models has shown that depriving the myocardium, as well as the brain and some other tissues, of oxygen for brief periods helps them survive more severe and prolonged ischemia later on.
Since the mid-1980s, scientists have been trying to find ways to exploit this phenomenon clinically to improve survival and recovery following heart attacks, strokes, and other ischemic events.
Some of this research has shown that brief ischemia in one part of the body can provide protection elsewhere, dubbed remote ischemic preconditioning.
Clinically, squeezing patients' arms enough to create distal ischemia has been found to help reduce cardiac damage resulting from surgery and angioplasty, during which blood flow to the heart may be stopped for long periods. (See Arm Squeezing Before CABG May Help Protect Heart)
Bøtker and colleagues tested the approach as a real-world treatment for ST-elevation myocardial infarction (STEMI) in emergency situations.
From February 2007 to November 2008, consecutive patients in the Aarhus area with suspected STEMI were randomized on the scene to receive standard care, either with or without four cycles of five-minute applications of a standard inflatable arm cuff, inflated to 200 mm Hg, during transport to the hospital.
Patients underwent revascularization on arrival, preceded by aspirin, clopidogrel (Plavix), and intravenous heparin. Abciximab (Reopro) was infused during the intervention and continued for 12 hours.
The primary outcome measure was the myocardial salvage index, determined with gated single photon emission CT (SPECT) imaging performed at admission and again at day 30.
A total of 333 patients were randomized, but more than half were dropped from the data analysis -- 32 lost to follow-up entirely, 77 because the SPECT imaging was not completed at day 30, and 82 because they failed to meet the study's inclusion criteria on arrival at the hospital.
Failure to confirm STEMI at the hospital and discovery of previous heart attacks were the main reasons for exclusion. One patient had a previous bypass graft and three had experienced chest pains more than 12 hours before treatment began.
The exclusions and losses to follow-up were almost equally divided between the treatment groups.
Differences in salvage index were significant for the means as well as the medians. The mean 30-day salvage index in the cuff group was 0.69 (SD 0.27), compared with 0.57 (SD 0.26) for the control patients (P=0.033).
The degree of salvage, as fraction of the left ventricle, was 16% with the cuff treatment versus 12% in the controls (P=0.037).
Final infarct size, which could be evaluated in some patients with insufficient data for salvage index, was 4% with the cuff compared with 7% in the controls (P=0.10).
There were no differences between groups in cardiac deaths, reinfarctions, or heart failure.
Bøtker and colleagues concluded that the remote ischemic preconditioning was beneficial, although they noted that salvage index is a surrogate endpoint.
"Our findings merit a larger trial to establish the effect of remote conditioning on clinical outcomes," they wrote.
The approach is especially attractive because of its simplicity and low cost, the researchers added. They also pointed out that it can be started by first responders and can be combined with thrombolytic drug therapy.
In an accompanying comment, two French physicians agreed that the treatment shows excellent promise.
"At a time of major difficulties in supporting the cost of our healthcare systems, Bøtker and colleagues have shown that a noninvasive, simple, safe, and cheap intervention, possibly done by a paramedic before hospital admission, can significantly increase myocardial salvage; they have also shown the benefit of an integrated prehospital and inhospital therapeutic strategy," wrote Michel Ovize, MD, PhD, and Eric Bonnefoy, MD, PhD, of the University of Lyon.
But they also echoed the need for additional, larger studies using clinically relevant outcomes.
The study was funded by Fondation Leducq.
No potential conflicts of interest were reported by study authors or the editorialists.
