A number of people online on other sites have self-identified as MDs and coroners and said that it is almost impossible to tell post mortem, what exactly caused cardiac arrest, in a wide variety (they listed some) of circumstances.
I have over 80 tabs open and I'm not going to go looking.
True. Cardiac arrest may come from the stress of a physical event. However, we see a knee down on a man’s carotid artery. That physical evidence is strong enough to consider it as the main cause of the cardiac arrest. You see, it is a chain of events: The cut off of blood flow to the brain, cuts off the supply of oxygen and glucose (sugar). This quickly causes brain death, like you would see from a person who has drowned. This brain death stops the lungs from the process of breathing. People who have drowned need to get their lungs working through artificial respiration quickly. Without the flow of oxygen from the lungs, the heart stops beating. Many times the heart is helped by repetitive pulses to the chest breast plate. However if the paramedics don’t get that person on a ventilator and the heart started with those electro-shock paddles, the person dies quickly.