years 19701993, while during 19942012, survival improved to 34 percent. A 2009 paper reported that survival drops to 3% when resuscitation is delayed beyond 3 minutes.< Higher survival rates correlated with immediate resuscitation by using CPR and an on-site automated external defibrillator—the survival rate was forty percent if resuscitation was performed within three minutes of the impact injury, contrasted with only five percent survival if resuscitation was delayed to more than three minutes after the impact. During the early 21st century, survival rates continued to improve to 58 percent of cases. Causes Sports Commotio cordis is a very rare event, but nonetheless it is often considered when an athlete presents with sudden cardiac death. Some of the sports which have a risk for this cause of trauma are baseball, American football, association football (soccer), ice hockey, polo, rugby football, cricket, softball, pelota, lacrosse, boxing, professional wrestling, hurling and martial arts (see Touch of Death). Children are especially vulnerable, possibly due to the mechanical properties of their thoracic skeleton. From 1996 to spring 2007, the USA National Commotio Cordis Registry had 188 cases recorded, with about half occurring during organized sports. Almost all (96%) of the victims were male, the mean age of the victims during that period was 14.7 years, and fewer than one in five survived the incident. Baseball is the most common sport in which commotio cordis occurs in regions where it is played, particularly among teenage boys who are batting or playing the positions of pitcher or catcher. Commotio cordis may occur in other sports via impacts to the chest by elbows or heads. It has also been reported outside of sports when there is sudden impact to the chest wall by hard objects or fists. Impact factors In experimental animal models in pigs studying impacts by a hard ball to the chest wall, impacts that occurred directly over the center of the left ventricle, where there is no overlying lung tissue, were the most likely to cause ventricular fibrillation. Impacts not over the heart did not cause ventricular fibrillation. Ventricular fibrillation was more easily induced in smaller, leaner animals. The velocity of the impact by a hard object is a critical factor for the onset of commotio cordis: impacts at were the most likely to cause ventricular fibrillation in an animal model. At velocities of , ventricular fibrillation did not occur. Impact energies of at least