A blow to the chest can cause sudden, cardiac death. It’s called commotio cordis. Essentially, the trauma causes a brief electrical spike. If it happens during a particular point of the cardiac cycle, it can stop the heart immediately. It is much much more common in young children due to the increased compliance of the chest wall. Most cases that I’ve ever heard of occur with a strike to the sternum, usually a punch or a ball – like in baseball or lacrosse.
It’s extremely rare. Only about 10 to 20 cases a year are reported. I don’t think I’ve ever heard of a case in anyone over the age of 20 years of age. Every case I’ve heard of, or attended to, involved baseball. I would think shoulder pads would prevent the anterior chest from this type of injury. Resuscitation was historically, dismal, but that is improved with better recognition. There is some speculation that certain individuals are more predisposed given a possible long QT syndrome. The variables that are necessary for this to occur, include the velocity and timing of the incident. Without going into the specifics of the cardiac electrical cycle and repolarization, the most common underlying dysrhythmias include long QT syndrome, and a condition called Brugada syndrome.
A blow to the chest does transmit electrical activity through the chest wall into the heart. Whenever I’m at the bedside and a patient’s heart stops the quickest way I have to get it restarted is a thump, essentially a punch into the chest of the patient. It is thought that a normal punch to the chest confers, approximately 2-5 J of energy.