Ventricular Fibrillation

Description

• Ventricular fibrillation (VF) is completely disorganized depolarization and contraction of small areas of the ventricle without effective cardiac output
• Cardiac monitor displays rapid grossly irregular electrical activity with electrocardiographic waveforms that are variable in length, morphology, and amplitude; ventricular rate is usually >300 bpm. There are no recognizable P, QRS complexes or T-waves

Etiology

• Damaged myocardium creates sites for re-entrant circuits:
  • Myocardial damage may be caused by multiple factors including ischemia, necrosis, reperfusion, healing, and scar formation
• Most often a result of severe myocardial ischemia:
  • ∼50% of VF-OHCA patients who survive to hospital admission have evidence of AMI
• Complication of cardiomyopathy:
  • Patients with structural heart disease are at a higher risk of sustained VT and VF
• Nonischemic causes of ventricular tachycardia may evolve into VF:
  • Drug toxicities (cyclic antidepressants, digitalis)
  • Electrolyte or acid–base abnormalities
  • Congenital and acquired prolonged QT syndromes
  • Short QT syndrome
  • Brugada syndrome
• Premature ventricular complexes (PVCs) with R-on-T phenomenon
• Other less common causes of VF:
  • Electrocution
  • Hypoxia
  • Hypothermia
  • Blunt chest trauma
  • Iatrogenic myocardial irritation from pacemaker placement or pulmonary artery catheter
• Idiopathic VF

• Primary ventricular dysrhythmias are extremely rare in children
• VF usually results from a respiratory arrest, hypothermia, or near drowning