When you start out reading an ecg looks a bit baffling. Don't worry. Like anything you'll get better at it the more you practice. Get those simulators out and keep trying to name those rhythms.
The normal ECG (Sinus)
You know what sinus is right! There is a P wave before every QRS. There is no delay between the P wave and the QRS complex. Each QRS is of normal appearance. A T wave follows each QRS. The QRS complexes are regularly spaced. The Iso-electric line between each part of the ECG is on the same level. (No ST depression or elevation) You know the rest.
Ventricular fibrillation (VF)
This is a very fast, irregular heart rhythm in the lower heart chambers (ventricles). During VF the heart quivers and pumps little or no blood to the body. Consciousness is lost in seconds. You can recognise it easily by those irregular tracings showing no organised rhythm at all, an incoherent trace (no stable cycle length, activation time, or vector. Therefore the end result is that no mechanical contraction occurs and there is no effective cardiac output.
Ventricular Ectopics (VE)
Ectopic means to arise somewhere other than the normal position. So Ventricular ectopics are beats which arise somewhere in the ventricular area of the heart. They are extra beats and do not normally effect cardiac output. They are recognisable as wide bizarre complexes which don't fit with the underlying rhythm of the ECG. Can you spot the ventricular ectopic in this strip?