Light blow to chest can be fatal. (Biomedicine).

Researchers collecting data about sudden heart stoppages among otherwise healthy people have made a disturbing observation: Light blows to the chest that hit the heart directly can cause it to misfire and stop in rare cases.

Six years ago, these same researchers published a preliminary report suggesting that this tragic occurrence--called by its Latin name commotio cordis, or chaotic heart--can result when baseball players are struck in the chest by a ball. An analysis of 125 heart stoppages indicates that commotio cordis has also occurred in hockey and karate participants and as the result of light blows to the chest that occur around the home, says Barry J. Maron, a cardiologist at the Minneapolis Heart Institute Foundation.

In the 1990s, Maron and his colleagues began documenting sudden heart stoppages, primarily in children. They analyzed cases dating to the1970s. Of the group in this study, 108 died. Survivors owe their lives to prompt use of cardiopulmonary resuscitation (CPR) or the availability and use of an electric defibrillator to restart the heart, Maron says. For this reason, all coaches should know CPR, he says.

A chest blow can be fatal if aimed directly over the heart and timed to a vulnerable split-second in the heart rhythm. The impact short-circuits electrical impulses that keep the heart beating, Maron says. The fatal contact doesn't bruise the heart, he emphasizes. "There's no structural damage anywhere," he says.

In 6 of the 108 deaths, prosecutors pursued homicide or manslaughter charges against children or adults who struck the blow that allegedly caused the death, Maron says.