Concepts in cardiac arrest are often confusing and misunderstood by most: 

Imagine cyclists riding up a hill, its pretty steep if they stop or slow down too much they will be overtaken by the race officials and ejected from the race. Some cyclists are further in front of the officials than others, they have a greater physiological reserve. Some are more persuasive at being able to continue, they are better at tolerating cerebral hypoxia. But everyone needs to keep going. 

Imagine a cyclist gets a flat tire (myocardial ischaemia), it could be fixed (angioplasty), it could be a little loss of air and he can continue slower (small MI with mild cardiogenic shock) or he could crash and fall (Cardiac Arrest). The damage to his bike could be different, his chain could come off (arrthymia) or any number of things, some fixable, some not. 

If he falls off and no one is nearby he will likely stay on the floor and ejected from the race. However if people get to him early enough, they can give him an effective push and get him moving again (effective CPR). They have not fixed the problem but he is just staying ahead of the officials. 

Sometimes his head is all over the place, he cannot think straight and he is going in circles (VF) he needs someone to shake some sense into him so he can get going again (Defibrillation and Return of spontaneous circulation, ROSC). Sometimes this takes a few attempts. Sometimes he needs some effective pushing before he is ready to be shaken to start again. If he gets going again he has to start on a hill, which is tough so he will probably need some support especially if he lost a lot of ground to the race officials (Post ROSC care).
If there is a flat tire and the team car (cath lab) is close enough, they can get to him and fix it so he can get going again (angioplasty). 

Some cyclists stop because they have not been getting enough sugar, they hit the wall, and their muscles do not get the fuel they need (coronary artery perfusion). In this state some people need a bit of help, like a tube of sugar squeezed into their mouths (vasopressors). It’s difficult to tell how much they need (some people use arterial lines to work out coronary perfusion pressure) as if they get too much they may feel sick. 

Some people think that they need someone screaming in their ears to GET UP AND GO GO GO! (inotropes and chronotropes) other people think that shouting at someone on the floor is unlikely to help if they have no sugar (coronary artery perfusion). 

Sometimes the coach is called (adrenaline), he does loads, he gives sugar and screams at the cyclist, in most places we call every coach we know and the cyclist gets a 100 coaches (1mg IV adrenaline) shouting at him and giving him sugar. This has been shown to get him up (ROSC) but a lot of the time he was only doing it for the coaches and slowly gives up over the next few weeks in front of his whole family with support teams and the world’s media desperately watching on thinking they were achieving great things (ITU). 

New evidence suggests that gagging the coach (giving esmolol with the adrenaline) may help; the coach (adrenaline) gives some sugar and does not shout so loud. This is an interesting approach and needs looking into further as we increasingly think the coach (adrenaline) may not actually benefit the cyclist in the way we are delivering it to him.
The best evidence is for an early push from spectators (bystander CPR) with an early shaking to get things going again if they are muddled (Defibrillation). 

Sometimes the shake does not work. People have looked into a double shake that shows some promise for people who are muddled that resists shaking (Refractory VF). 
Another option if the cyclist’s team has loads of cash, time and resources is to drive a team care next to him lean out the window grab him and tow him up the hill (ECMO). 

Steve Young
@steveyoungmedic