Ventricular Fibrillation

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Contents 1 More Specific Terms 2 Introduction 3 Etiology 4 Diagnostic-procedures 5 Management 6 More General Terms 7 References

More Specific Terms

• paroxysmal familial ventricular fibrillation; idiopathic ventricular fibrillation

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
• check rhythm on monitor & pulse after each 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,
• 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 [2,3]
• 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
• bretylium 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 is next recommended route of access for administering drugs during CPR

• # vasopressin not helpful [4]

More General Terms

• ventricular tachycardia (VT)

References

1. Manual of Medical Therapeutics, 28th ed, Ewald & McKenzie (eds), Little, Brown & Co, Boston, 1995, pg 148-49, 175-176
2. Journal Watch 22(9):68, 2002 Dorian P et al, N engl J Med 346:884, 2002
3. ACLS - The Reference Texbook ACLS: Principles & Practice, Cummins RO et al (eds), American Heart Association, 2003 ISBN 0-87493-341-2
4. Gueugniad P-Y et al, Vasopressin and epinephrine vs epinephrine alone in cardiopulmonary resuscitation. N Engl J Med 2008, 359:21 PMID: [1]

ventricular fibrillation (V Fib)