Wider dissemination of portable defibrillators in Japan’s schools, workplaces and other public venues has increased the number of people who survive cardiac arrest, researchers reported Wednesday.

Experts say the findings, reported in the New England Journal of Medicine, support efforts to make the devices, known as automated external defibrillators (AEDs), more widely available for laypeople to use.

Cardiac arrest is a medical emergency that is quickly fatal without prompt treatment. Most cases occur when the heart goes into ventricular fibrillation (VF), a heart-rhythm disturbance in which the heart begins to quiver chaotically and can no longer pump blood to the body.

An Electrical shock from a defibrillator can restore the heart’s normal rhythm and reverse cardiac arrest. AEDs are a portable, layperson-friendly version of the devices that automatically analyze the heart’s rhythm and, if needed, instruct the user to deliver a shock.

In recent years, AEDs have been placed in a growing number of public areas - including schools, transportation hubs, offices, malls and sports venues - with the goal of getting potentially life-saving treatment to more cardiac-arrest victims.

Exactly how effective those measures have been on a large scale has been unclear.

For the new study, researchers led by Dr. Tetsuhisa Kitamura, of the Kyoto University Health Service, analyzed a national database with information on more than 300,000 Japanese adults who suffered cardiac arrest outside of a hospital between 2005 and 2007. In 2004, Japan made it legal for any citizen to use an AED, and public AEDs became increasingly available over the study period.

Overall, the study found, 12,631 people in the database suffered a cardiac arrest in front of witnesses. Just 14 percent survived and had minimal brain damage one month later.

But among the 4 percent of victims who received an AED shock from a layperson bystander, 32 percent survived with little to no brain damage.

Over the study period, the proportion of cardiac arrests treated with a public AED rose from 1.2 percent to 6.2 percent as the availability of the devices grew. And cardiac arrest survival was greater in geographic areas with more AEDs.

The study “provides support for the concept of public-access defibrillation,” Kitamura’s team writes, “and should encourage other countries or communities to promote public-access-defibrillation programs.”

“Because the incidence of sudden cardiac arrest is greater in the US and European countries than in Japan, public-access AEDs would be more effective than that shown in this study,” Dr. Taku Iwami, a co-author on the study, added in an email to Reuters Health.

Dr. Michael Sayre, spokesman for the American Heart Association (AHA), told Reuters Health that this study “shows the kind of public health impact that placing AEDs in public areas could have.”

Sayre, of Ohio State University in Columbus, added that the AHA supports wider placement of AEDs in public areas, like sports venues, malls and office complexes.

An obstacle is cost, Sayre noted, since the odds of needing to use an AED at any single venue are fairly low, and some sites might not want to invest in the devices. AEDs typically cost between $1,500 and $2,000.

And wider AED placement is not enough on its own. It’s still up to bystanders who witness a person collapse to quickly get help - calling 911 and alerting personnel who will know where the site’s AED is.

Sayre pointed out that in many places with AEDs, at least in the U.S., “there’s no good way” for bystanders to know that the devices are present. And many people may not know what AEDs are, for that matter.

Ideally, according to Sayre, public sites that invest in AEDs should have designated people who know where the devices are located and how to use them - even though they are designed for untrained people to be able to use when necessary.

Performing CPR until the AED is applied also remains vital. It’s estimated that a cardiac-arrest victim’s chances of survival drop 10 percent for each minute defibrillation is delayed; using CPR to keep the person’s blood circulating improves those odds.

SOURCE: The New England Journal of Medicine, March 18, 2010.