It has been theorized that presenting prehospital ECG could guide resuscitative efforts. 332 out of hospital cardiac arrests in PEA were prospectively enrolled. The rhythm was studied for HR, QRS interval and presence of P waves, and determined their impact on return of spontaneous circulation and survival to hospital discharge. It was concluded that ALS presence and successful ETI were associated with survival but not ECG findings in PEA victims.

https://www.ncbi.nlm.nih.gov/pubmed/?term=ho+AND+utility+of+prehospital+electrocardiogram