ACLS Basics and STEMIs Practice Test 2026 - Free ACLS Practice Questions and Study Guide

In ventricular fibrillation the heart’s electrical activity is chaotic, so there is no coordinated contraction or effective cardiac output. The only intervention that can rapidly restore an organized rhythm is defibrillation, which delivers a shock to depolarize a critical mass of heart muscle and reset the electrical activity. This momentary reset gives the heart a chance to resume a normal rhythm, ideally the normal sinus rhythm. Medications like epinephrine support perfusion but don’t convert the chaotic rhythm by themselves, and increasing oxygen or providing CPR maintains circulation and oxygenation while you attempt shocks. Pacing isn’t effective in true VF because there’s no organized rhythm to pace. So, defibrillation is the key intervention to restore an organized rhythm.