Ok. CAD is most common. However....
BTW thanks.
1. If cardiac standstill was caused by something besides CAD or electrocution, etc., but by an etiology which it takes a hospital to detect and/or clear up, then the hospital trumps the truck. Something like pericardial tamponade, poisoning, sucked valve will create a time-dependent descending "glass ceiling" to field resuscitation measures and there is little which can be done on scene save gather data and try to maintain circulation, and know when to gather petticoats and book outta there.
2. Although on scene care is eminently important, it is not definitive. IF you slug it out for forty-five minutes post arrest in the patient's living room and you get a pulse, then you have the ride to the hospital. If you can do more enroute, then forty-five minutes post arrest the patient may be on a pacer, being cardioverted in a controlled setting, getting meds dictated by more sophisticated diagnostic procedures, etc etc. Talking to Billing Department.
3.Given that in the field a "cardiac arrest" can have an etiology not apparent in some cases to field staff; or, it is complicated by other processes like diabetes, trauma, poisoning, pericardial tamponade, congenital heart defect, etc.; or the etiology is not addressable in the field (sucked valve, ETOH heart) ; then the pt will likely be dispatched and classified/diagnosed as having a primary issue of cardiac arrest but the treatment must very promptly go beyond just trying to reestablish circulation; the pulseless state is a symptom, albeit a lethal one. Also, prolonged field treatments do not have the opportunity to address side effects such as emergent polypharmacy (using lots of different chemicals on top of the pt's current meds, causing an unavoidable upset of homeostasis), pH and electrolyte shifts. Not to mention mechanical trauma of CPR, or other iatrogenic trauma.
If such a patient is delivered organically as well as clinically dead, or irretrievably close to it, it can be written off because the cardiac arrest's etiology (which a hospital might have addressed) is considered secondary to asystole as cause of death. THEN yes, the hospital is considered to be inferior to field, but that is because of a conceptual error.
PS: I rewrote this twice to try to make it simpler but not as blunt as "we bury our mistakes and it isn't our fault always").