Cardiac arrest is the sudden loss of heart function, typically resulting from an abnormal heart rhythm that causes the heart to quiver erratically and stop pumping blood. According to the American Heart Association, effective bystander CPR provided immediately after sudden cardiac arrest can double or triple a victim's chance of survival.

In a review of 547,218 cardiac arrests occurring in 2005-09, researchers identified almost 140,000 incidents witnessed by bystanders without a physician's involvement. Bystander groups studied included family members, friends and colleagues, passers-by and others.

Researchers found:

-- The time interval between collapse and emergency call and between call and arrival to patients was shortest when witnessed by passers-by.
-- Family members were least likely (36.5 percent) to administer CPR, but most likely to receive telephone instructions from dispatchers (45.8 percent).
-- The telephone instruction to family members most frequently failed (39.4 percent) and family members most often used chest compressions only (67.9 percent).

"If you go into cardiac arrest in front of your family, you may not survive," said Hideo Inaba, M.D., Ph.D., lead author of the study and professor and chairman of the Department of Emergency Medical Science at Kanazawa University Graduate School of Medicine in Kanazawa, Japan. "Different strategies, including basic life support instruction targeting smaller households, especially those with elderly residents, would improve survival, as would recruiting well-trained citizens willing to perform CPR on victims whose arrest was witnessed by family members."

CPR provided by family members may have been ineffective due to their lack of knowledge or fear of injuring their loved one, said Inaba. Cultural and demographic issues in Japan, which has a large gender gap, may also have contributed to the findings, he said.

In a study conducted in 2008, researchers found that Japanese women were less likely to attempt CPR. Men accounted for a majority of cardiac arrests in the current study, and their wives or daughters-in-law witnessed most of them, researchers said.

Japan has a rapidly aging population, with elderly people, mostly couples, in 42 percent of households in 2010, Inaba said.

"These characteristics of Japanese households might have contributed to our observations and may be different from households in the United States," Inaba said. "Also, the percentage of older persons in Japan is larger than in the U.S. population. So the results may be less applicable."

Furthermore, the database didn't include the exact location of each cardiac arrest, although basic life support response and outcomes differ between locations. The type of bystander who responds is also closely related to the location of the cardiac arrest.

Co-authors are: Takahisa Kamikura, M.D.; Tetsuo Maeda, M.D.; Yoshitaka Hamada, M.D., Ph.D.; Satoru Sakagami, M.D., PhD; and Taiki Nishi and Keiko Takase, master course students.

Author disclosures are on the abstract.

Learn more about the American Heart Association's efforts to promote CPR.

Follow news from the American Heart Association's Scientific Sessions 2012 via Twitter: @HeartNews.

Statements and conclusions of study authors that are presented at American Heart Association scientific meetings are solely those of the study authors and do not necessarily reflect association policy or position. The association makes no representation or warranty as to their accuracy or reliability. The association receives funding primarily from individuals; foundations and corporations (including pharmaceutical, device manufacturers and other companies) also make donations and fund specific association programs and events. The association has strict policies to prevent these relationships from influencing the science content. Revenues from pharmaceutical and device corporations are available at www. heart.org/corporatefunding.

Note: Actual presentation is 11:30 a.m. PT/ 2:30 p.m. ET Sunday, Nov. 4, 2012 in the Gold Ballroom at the JW Marriott at LA Live.

All downloadable video/audio interviews, B-roll, animation and images related to this news release are on the right column of the release link at http://newsroom.heart.org/pr/aha/_prv-japanese-family-members-less-like ly-239557.aspx.

Video clips with researchers/authors of studies will be added to the release links after embargo. General B-roll and Photos

The American Heart Association logo is available at http://www.globenewswire.com/newsroom/prs/?pkgid=9940

For Media Inquiries:

AHA News Media in Dallas: (214) 706-1173

AHA News Media Office, Nov. 3-7

at the Los Angeles Convention Center: (213) 743-6205

For Public Inquiries: (800) AHA-USA1 (242-8721)

heart.org and strokeassociation.org