ventricular fibrillation (V Fib)

Introduction

Ventricular fibrillation (V Fib) occurs as the result of uncoordinated electrical activity within the ventricle resulting in ineffective ventricular contraction, hemodynamic collapse & death.

Etiology

• Any structural, metabolic or toxic condition that adversely affects generalized electrical recovery & repolarization of the ventricular myocardium can precipitate ventricular fibrillation.
  • myocardial ischemia or infarction
  • hypoxemia
  • acidosis
  • electrolyte abnormalities
  • drug toxicity
• artifact, patient movement, other can masquarade as ventricular fibrillation

Diagnostic procedures

• electrocardiogram:
  • irregular oscillations in baseline without p-waves, QRS complexes or T waves
  • 250-400/min

Management

ventricular fibrillation or pulseless ventricular tachycardia

• CPR until defibrillator available
• cardiac monitor
• immediate unsynchronized DC cardioversion
  • defibrillate up to 3 times with 200, 300, 360 joules
  • continue with CPR for 2 minutes or 5 cycles of 30 chest compressions & 2 breaths
    • ineffective cardiac output from myocardial shock may occur for up to 2 minutes after restoration of viable rhythm
  • check rhythm on monitor & pulse prior to subsequent defibrillation
• cardiopulmonary resuscitation until cardioversion is successful*
• intravenous (IV) access
• epinephrine 1 mg IV push, or vasopressin 40 units IV (single dose only)#
  • repeat every 3-5 min (guideline)
    • intervals shorter than 3 minutes may increase odds of survival with favorable neurologic outcome
  • defibrillate with 360 joules after each dose
• defibrillate with 360 joules
• for persistent or recurrent VF/VT (i.e. 2nd shock), administer medications of probable benefit in the following sequence:
  • amiodarone 150 mg IV over 10 minutes
  • lidocaine 1.0-1.5 mg/kg IV push, repeat every 3-5 min, max 3 mg/kg (2-3 doses)
  • magnesium sulfate 1-2 g IV
  • procainamide 30 mg/min, max 17 mg/kg
  • defibrillate with 360 joules after each dose of medication
• following successful cardioversion, continuous infusion of lidocaine 0.5-0.75 mg/kg, then continuous infusion procainamide until acute alterations in the electrophysiologic substrate have been corrected
• primary ventricular fibrillation within 72 hours of an acute MI is not associated with an increased risk of future episode(s)
• ventricular fibrillation without an identifiable or reversible cause
  • prophylactic antiarrhythmic therapy - amiodarone
  • implantation of an automatic defibrillator
• a solid precordial thump may convert VF of VT to a stable rhythm if delivered quickly after a witnessed arrest in a pulseless patient - considered a class IIb intervention
• if IV access is unsuccessful, intraosseous infusion is next recommended route of access for administering drugs during CPR
• stress dose of hydrocortisone may be of benefit for post- resuscitation shock
• if patient survives, he/she should be offered an ICD

* unconscious adults with return of spontaneous circulation after out-of-hospital cardiac arrest be cooled to 32 to 34 Celsius for 12 to 24 hours when the initial rhythm was ventricular fibrillation

# vasopressin not helpful

# vasopression 20 units plus methylprednisolone 40 mg (first dose only) in addition to epinephrine improves outcomes

More general terms

• ventricular tachycardia (VT)
• fibrillation

More specific terms

• paroxysmal familial ventricular fibrillation; idiopathic ventricular fibrillation