Serious Head Trauma Lead to Cardiac Arrest?

An individual was running at a relatively fast pace in the rain without shoes chasing a frisbee.  The frisbee was thrown toward a parked car individual ran to catch frisbee (not smart idea, but irrelevant), realized they could not catch it in time then a combination of putting hands out to brace for impact and slipping while slowing down/contacting car and slammed back on pavement then whiplash smashed head to pavement.  Very minor contact with car, slipped almost immediately after contact.  Individual did not move, tensed up eyes rolled back (911 called at this point) starting seizuring, no pulse, mouth to mouth given/chest compressions (performed by vol firemen aka informed enough) ambulance arrives AED advised shock and it was performed.  This individual is now in much better shape and is currently in the hospital with minimal injuries.

Now, a leading doctor at this hospital claims that there is no way a head trauma like the one experienced, or any for that matter, could cause the victim to enter cardiac arrest.  The view is that this victim had to have had entered cardiac arrest possibly while running or at some point along the way, but NOT from the actual head trauma.  Maybe hereditary condition (but unbeknownst to individual).  Of course every necessary test has been performed on victim and it was accepted early on that the head trauma caused the cardiac arrest until certain doctor said otherwise (this was of course after every doctor had signed off on the patient, and was ready to leave).

Hospital/doctor competency or unclear doctor communication channels not necessarily issue (at least for the purpose of this post).  This issue is again can serious head trauma, such as the one illustrated above lead to cardiac arrest?

[Dr. Kokil Mathur]

Hi!
Since I have not seen the case records, nor I was there in this case, so I cannot say for sure whether this is applicable in this patient's case, but yes, traumatic brain injury can cause cardiac arrest. If the injury involves brain stem (cardiovascular shock/arrest secondary to respiratory arrest) or it cause severe arrhythmia or if the injury was a huge shock, then yes, it can cause a cardiac arrest. Excess blood loss, or possible heart disease (maybe undetected) and hypovolumic shock can cause secondary cardiovascular shock.
However, whether this holds true is this case or not, I cannot ascertain, as a seemingly simple impact can cause major head injury, and vice versa.
Take care!