I think the "blow to the chest" may also be describing "cardiac concussion". Here's an article from my local paper on the subject, focusing on youth sports:
Cardiac concussion
excerpt:
"The cause is a little-known medical event called commotio cordis, or cardiac concussion. It occurs when an athlete suffers a blow to the chest in a specific time between beats of the heart. The organ goes into ventricular fibrillation, or some other irregular heart rhythm, and then cardiac arrest. Though it occurs most often in baseball, it also has been reported in softball, ice hockey, lacrosse, boxing and fights, and in vehicular accidents."