Basic Arrhythmias With 12 Lead EKG's Practice Test

Ventricular fibrillation reflects severe electrical instability of the ventricles, most often precipitated by acute extensive ischemia from a large myocardial infarction. When a big region of the heart muscle becomes ischemic and damaged, conduction becomes highly heterogeneous and areas of the ventricle fire in an uncoordinated, chaotic pattern. Ion-imbalance and cell injury during a large infarct promote this rapid, disorganized activity, so the heart can no longer pump effectively.

Other conditions may cause different problems, but ventricular fibrillation is most classically linked to a large or transmural myocardial infarction, which creates the widespread electrical disruption that leads to fibrillation.