The hearts action potential. Because of the unique set up the heart can beat independently without the nervous system stimulating it to contract! your heart can still beat after being removed from your body!
This is the commonest fatal arrhythmia in ischemic heart disease. The myocardium of the ventricles contract asynchronously and fractionally to produce a fibrillary movement without any sustained synchronous beat.
The action potentials from an atrial (green curve) and a ventricular fibre (blue curve) are show. The direction of propagating waves in the frontal plane is shown on the right, with their relation to the ECG waves.