Ventricular Fibrillation & Cardiac Arrest

Ventricular fibrillation produces no effective heartbeat and zero cardiac output — the patient is clinically dead until you intervene. Seconds determine whether they stay that way.

Ventricular fibrillation (VF) is a chaotic, disorganized quivering of the ventricles that produces no effective contraction and therefore no pulse. On the monitor, VF appears as an irregular, wavy baseline with no identifiable P waves, QRS complexes, or T waves. Coarse VF has larger-amplitude waveforms and responds better to defibrillation than fine VF, which looks almost like asystole. VF is a shockable rhythm — the definitive treatment is immediate defibrillation, not synchronized cardioversion. Each minute without defibrillation reduces survival by roughly 7–10%. While waiting for or between shocks, high-quality CPR is the priority: compressions at 100–120/min, depth of at least 2 inches in adults, full chest recoil, and minimal interruptions. After the first shock, resume CPR immediately for 2 minutes before rechecking rhythm. Epinephrine 1 mg IV/IO is given every 3–5 minutes. If VF persists after the second shock, amiodarone 300 mg IV push is the first-line antiarrhythmic, followed by a second dose of 150 mg if needed. Pulseless electrical activity (PEA) and asystole are non-shockable — recognizing which arrest rhythms get a shock versus CPR-only is a critical NCLEX distinction.

Key Distinctions

Don't confuse VF (shockable, chaotic waveform, no pulse) with asystole (non-shockable, flat or near-flat line, no pulse) — shocking asystole is always wrong. Students mix up defibrillation (unsynchronized, used for VF/pulseless VT) with synchronized cardioversion (used for unstable tachycardias with a pulse). Fine VF can mimic asystole — check in two leads before calling a flat line.

Clinical Pearl

Shock VF, don't shock asystole. If the monitor looks flat, confirm in two leads — fine VF hiding as asystole still needs a shock.