Former EMS worker here: It's interesting to compare the EMS responses to Graham and McConnell. Both were reportedly "cardiac arrests", but the similarity ends there.
In McConnell's case, the 911 caller REPORTED a cardiac arrest, but that's all but meaningless. People often call any heart thing a cardiac arrest.
In Graham's case, the EMS workers reported doing CPR, meaning he was actually in cardiac arrest, which has a very low survival rate if CPR hadn't already started before EMS got there.