Just because people have been asking I will try to break down what apparently happened. Keep in mind that this is all speculation based on limited evidence. He is not my patient.
Based on the facts we know:
-He took a hit to the chest
-He was able to stand up but then collapsed and was reported to be in cardiac arrest
-He was given CPR immediately and was given an electric shock to restart his heart
-He had no prior known heart disease
-He is in critical condition and may have some lung injury
First of all, he was an elite athlete. I don’t know for sure but I would certainly suspect that he had been screened for obvious cardiac abnormalities with at least an EKG and an echocardiogram at some point so he is unlikely to have had any major undiagnosed prior cardiac issues. While undisclosed arrythmias can occur at any time, it is most likely that his condition was related to the tackle.
The fact that he was shocked means his heart had not stopped. The purpose of defibrillation/cardioversion is to take a person whose heart is beating erratically and temporarily stop it to try to resume a normal rhythm. This by report was successful. Therefore, we can probably assume a severe arrhythmia ( most likely ventricular fibrillation) either spontaneous or more likely related to the tackle.
What likely happened was that as a result of the hit, his heart was jolted into an irregular rhythm that did not give enough blood flow to the rest of the body. He would have had enough residual blood to the brain to stand up momentarily before passing out.This happens if the blow to the chest occurs at just the wrong point in the cardiac cycle ( R on T phenomenon).
The most likely etiology as noted above is commotio cordis. In this situation, a blow to the chest hits at just the wrong part of the cardiac cycle, causing an arrhythmia. This is most common in athletes, especially young men and is seen when a player is struck in the chest by a baseball, for example. This would be an atypical case because it usually occurs under age 20 and is usually related to being hit by a projectile. However, while atypical, it certainly fits the course of events.
Recovery from cardiac arrest in the field is notoriously poor although improving. Some recent estimates for eventual hospital discharge are up to 11% out of hospital and 25% in hospital if treated promptly by EMS. He has a high chance of survival given that he is young and presumably in good health prior.
However, up to 40% of survivors of cardiac arrest have long terms medical problems. Again, he is at low risk because he did not have known preexisting conditions, and he was resuscitated quickly. However, recovery of brain function depends not only on how quickly CPR was started but in how efficient it was. He was treated quickly and presumably by a well-trained team, meaning that he probably received early effective CPR which may have included rescue breathing as the team had more than one member and probably has access to a bag and mask device (for solo resuscitation, rescue breathing is no longer recommended since the emphasis is on chest compressions).
Finally, he is reported to have lung problems. This could be related to damage from the hit, or even from CPR (effective CPR can break ribs if done correctly).
Right now, he is likely being sedated and monitored. He may be on a ventilator, allowing his lungs some time to heal.
In terms of recovery, neurological recovery is a wait and see proposition. Early treatment means less time of brain hypoxia and less brain injury but we don’t know if he has underlying damage from years of football. His heart will need to be checked for evidence of any blockages and he will most likely end up with an implanted defibrillator in case this happens again.
Sorry, this is so long. Again, just my opinion based on the video and reports I have seen.
tl:dr https://www.ahajournals.org/doi/full/10.1161/circep.111.962712