Hypokalaemia, Long QT syndrome and arrhythmia'sWatch
If someone was to have a cardiac arrest from the thingies mentioned above, would it be at all possible to survive with just CPR?
Is there a chance of a ROSC?
Yes its possible. Shockable rhythms are better than asystole, and those things may well cause a shockable rhythm. You'd want to get the defib on them ASAP.