See the ACLS guidelines.
What will they do in an ED to treat cardiac arrest that won’t be done prehospital?
What happens in the ER is way beyond ACLS. Medics start ACLS to get the patient a better outcome when they get to the ED. In the ED they can do rapid sequence intubation/LMA/cricothyroidotomy/video laryngoscopy, chest tubes, thoracostomy, CV cath placement, pericardiocentesis, thoracotomy, TC pacing, anything open chest/cardiac massage, the last try of solumedrol, etc...
in New York they cover pts with ice.
Also probably not a cardiac Cath lab available in the field, so if you do get a turnaround you can act on a blockage.