Ventricular fibrillation (VFib) is a lethal cardiac arrhythmia characterized by chaotic, disorganized electrical activity in the ventricles. Multiple wavefronts of depolarization occur simultaneously, producing a completely erratic pattern without identifiable P waves, QRS complexes, or T waves. The ventricular myocardium quivers rather than contracts in any coordinated fashion, resulting in zero effective cardiac output — this is cardiac arrest. Without immediate intervention, VFib is fatal within minutes. VFib is classified by amplitude: coarse VFib (higher amplitude, more recently onset, more likely to respond to defibrillation) and fine VFib (lower amplitude, longer duration, poorer prognosis, may be confused with asystole — check in two leads). The most common cause of VFib in adults is acute myocardial ischemia/infarction. The pathogenesis involves: (1) ischemia creates areas of varied refractoriness in ventricular tissue, (2) PVCs or VTach may trigger the initial fibrillatory event, (3) multiple re-entry circuits fragment into chaotic depolarization, (4) without defibrillation, the amplitude diminishes as ATP stores deplete, transitioning from coarse to fine VFib and eventually asystole. The only effective treatment is immediate defibrillation — for every minute without defibrillation, survival...