• Clinical science

Ventricular fibrillation


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.




  • Normal electrical conduction can be disrupted by re-entry → chaotic, circulating excitation of the myocardium (= ventricular fibrillation); → simultaneous contractions at multiple foci → insufficient cardiac output → hemodynamic collapse → loss of consciousness and possibly death (sudden cardiac death)
  • Re-entry can be caused by


Clinical features

  • Possible early signs
    • Chest pain
    • Palpitation
    • Fatigue
    • Shortness of breath
    • Dizziness
  • Ultimately: loss of consciousness, death



ECG findings

Evaluation of underlying conditions

  • Conducted during or directly after initial management of patients
  • ECG: specific findings may indicate underlying condition (see above)
  • Laboratory
  • Imaging



  • Resuscitation for V-fib
  • Post-resuscitation care
    • Intensive care monitoring
      • Control/management of vital signs and removal of acute metabolic imbalances (e.g., electrolyte disturbances)
      • Mild therapeutic hypothermia
    • Maintain application of antiarrhythmics that were used during successful resuscitation (usually IV amiodarone or IV lidocaine)
    • Consider administration of beta blockers
    • Treat underlying causes (e.g., treatment of CAD)
    • ICD; (implantable cardioverter-defibrillator) in patients without a readily reversible or treatable cause and/or with a high risk of recurrent, hemodynamically significant V-fib