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Ventricular fibrillation

Last updated: February 15, 2021

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Ventricular fibrillation ("VF" or "V-fib") is a life-threatening cardiac arrhythmia characterized by disorganized, high-frequency ventricular contractions that result in diminished cardiac output and hemodynamic collapse. V-fib usually begins with ventricular tachycardia and appears as a very irregular rhythm with indiscernible P waves or QRS complexes on ECG. The most common underlying condition is coronary artery disease, but V-fib may also be caused by other cardiovascular diseases or external factors (e.g., drugs, electricity). V-fib is frequently preceded by ventricular flutter (“V-flut”), which features very rapid sinusoidal QRS complexes that can not be distinguished from T waves. Some patients with V-fib may present with early signs, including chest pain, palpitations, and dizziness. However, V-fib usually causes sudden hemodynamic instability that results in loss of consciousness and, ultimately, sudden cardiac death. Therefore, immediate defibrillation and resuscitation are vital for survival.

ECG findings

  • Ventricular fibrillation
  • Ventricular flutter: ventricular rates of ∼ 240–300 bpm
    • Frequently transitions to V-fib

Evaluation of underlying conditions

  • Conducted during or directly after initial management of patients
  • ECG: specific findings may indicate underlying condition (see above)
  • Laboratory
    • Cardiac enzymes
    • Electrolytes
    • TSH
    • Drug levels and toxicology screen
    • Arterial blood gases
  • Imaging
  1. Hillier K. Magnesium Sulfate. Elsevier ; 2007 : p. 1-5
  2. Herold G. Internal Medicine. Herold G ; 2014
  3. Ventricular fibrillation. Updated: May 5, 2015. Accessed: February 26, 2017.