Ventricular fibrillation

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Diagnostic approach

• ABCDE survey
• Targeted clinical evaluation
• Rhythm strip
• POC glucose
• BMP
• Magnesium
• Blood gas analysis

Management checklist

• Follow ACLS for shockable rhythms.
• Initiate CPR and perform 1^st defibrillation as soon as possible.
• Resume CPR for a 2-minute cycle.
• Pause CPR for a rhythm and pulse check.
• If rhythm is still V-fib , perform 2^nd defibrillation.
• After 2^nd defibrillation: epinephrine repeated every 3–5 minutes
• After 3^rd defibrillation: Full-dose amiodarone OR lidocaine
• After 5^th defibrillation: Half-dose amiodarone OR lidocaine
• Identify and treat reversible causes of Vfib
• If ROSC: Begin post-resuscitation care, including repeat ECG.

Ventricular fibrillation (Vfib) is a life-threatening, pulseless arrhythmia that results in cardiac arrest and requires immediate cardiopulmonary resuscitation and defibrillation according to advanced cardiac life support (ACLS) protocols. Patients may experience prodromal symptoms such as palpitations, dizziness, and chest pain before Vfib rapidly results in loss of consciousness due to hemodynamic collapse. The most common cause is ischemic heart disease (e.g., acute myocardial infarction); other causes include heart failure, cardiomyopathy, electrophysiological disorders, and electrolyte abnormalities. The diagnosis is confirmed by ECG, which shows a chaotic and irregular waveform with no discernible P waves, QRS complexes, or T waves. After return of spontaneous circulation (ROSC), management focuses on identifying and treating the underlying cause and tertiary prevention with an automated implantable cardioverter-defibrillator (AICD).

• Underlying cardiovascular disease ^[2]
  • Most common: ischemic heart disease; (e.g., acute coronary syndrome, previous myocardial infarction)
  • Myocarditis
  • Cardiomyopathy
  • Heart failure
  • Valvular heart disease
  • Congenital heart defects (e.g., tetralogy of Fallot, aortic stenosis)
  • Electrophysiological disorders
    • Wolff-Parkinson-White syndrome ^[3]
    • Long-QT syndrome → torsades de pointes ^[4]
    • Brugada syndrome ^[2]
• Electrolyte abnormalities (e.g., hypokalemia, hyperkalemia) ^[5][6]
• Precipitating drugs, e.g., drug-induced long QT syndrome, drug-induced Brugada syndrome, stimulant intoxication, tricyclic antidepressant (TCA) overdose, cardiovascular drug poisoning ^[2]
• Commotio cordis, blunt cardiac injury ^[7][8]
• Electrical injury ^[9]

• Normal electrical conduction can be disrupted by re-entry; → chaotic, circulating excitation of the myocardium (= Vfib); → 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
  • Changes to the conduction pathway; (e.g., unexcitable scar tissue as a result of past myocardial infarction)
  • Abnormal pattern of excitation, for example:
    • If the period of activation and recovery of myocardial cells becomes greater than the duration of an action potential (as in long-QT syndrome)
    • If excitation occurs outside of the normal pattern of activation (premature ventricular complex, PVC )

• Rapid loss of consciousness and cardiac arrest: requires immediate CPR and defibrillation
• Possible early signs
  • Chest pain
  • Palpitation
  • Fatigue
  • Shortness of breath
  • Dizziness

Approach ^[2]

• Identify Vfib based on ECG or rhythm strip.
• Begin initial management of Vfib immediately.
• Evaluate for underlying causes of Vfib concurrently with CPR and defibrillation or as soon as feasible; see also "Reversible causes of cardiac arrest."

ECG findings ^[2]

• Ventricular fibrillation
  • Arrhythmic, fibrillatory baseline; , usually > 300/minute
  • Erratic undulations with indiscernible QRS complexes
  • No atrial P waves
  • No T waves
  • Commonly preceded by ventricular tachycardia
• Ventricular flutter
  • Ventricular rates of ∼ 300/minute
  • Regular, monomorphic, sinusoidal waveform
  • Can degenerate into Vfib

Initial management of Vfib ^[2][10]

Vfib is a pulseless shockable rhythm; follow standard cardiac arrest protocols.

• All patients: Begin ACLS.
  • Immediate CPR and defibrillation; see "Acute management checklist for shockable rhythms."
  • Administer amiodarone and lidocaine according to the ACLS algorithm.
  • Concurrently manage acutely reversible causes of cardiac arrest.
• No response or unclear response to ≥ 3 standard shocks (i.e., persisting Vfib) ^[10]
  • Troubleshoot standard defibrillation technique, e.g., check pad contact and energy dosage.
  • The benefits of alternative shock techniques (e.g., double sequential defibrillation), procainamide, bretylium, and sotalol are unclear in persisting Vfib. ^[10]
• ROSC achieved: Begin post-resuscitation care.
  • Secure the airway.
  • Maintain target respiratory and hemodynamic parameters.
  • Obtain ECG to:
    • Identify patients who need PCI after ROSC.
    • Screen for ECG red flags for sudden cardiac death, e.g., accessory pathways, prolonged QTc, epsilon wave, Brugada pattern.
  • Initiate targeted temperature management for persistently unresponsive patients.^[11][12]
  • Admit to ICU. ^[13]
• Recurrence of Vfib after ROSC: Treat as electrical storm and consider IV antiarrhythmic infusions (e.g., beta blockers). ^[10]

Do not routinely administer calcium, magnesium, or sodium bicarbonate to treat Vfib. ^[10]

Further management ^[2]

• Further evaluation and management of underlying causes of Vfib: based on clinical suspicion and under specialist guidance
  • Cardiovascular disease (e.g., acute coronary syndrome)
    • Cardiac biomarkers
    • Echocardiography
    • PCI after ROSC
    • Other cardiac imaging (e.g., cardiac MRI)
  • Drugs that can induce Vfib, e.g., cocaine, TCAs, digoxin ^[2][14][15]
• Tertiary prevention: depends on the underlying cause
  • AICD implantation: indicated for patients with an irreversible cause of Vfib and expected survival of > 1 year (See also "Indications for AICD.") ^[2]
  • Definitive treatment of the underlying cause of Vfib (e.g., antiarrhythmics, ablation) under specialist guidance

• One-Minute Telegram 65-2022-2/3: Better outcomes with alternative defibrillation strategies

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