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.

• Underlying cardiovascular disease
  • Most common: coronary artery disease (CAD)
  • Others: previous myocardial infarction, myocarditis, cardiomyopathy; , severe congestive heart failure, heart valve disease
• Congenital heart defects (e.g., pulmonary atresia)
• Electrolyte imbalances (e.g., hypokalemia, hyperkalemia) ^[1]
• Electrophysiologic disorders
  • Wolff-Parkinson-White syndrome
  • Long-QT syndrome → torsade de pointes

• 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
  • 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 )

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

ECG findings

• Ventricular fibrillation
  • Commonly preceded by ventricular tachycardia
  • General appearance
    • Arrhythmic, fibrillatory baseline; , usually > 300 bpm
    • Erratic undulations with indiscernible QRS complexes
    • No atrial P waves
• Ventricular flutter: ventricular rates of ∼ 240–300 bpm
  • Frequently transitions to V-fib

Evaluation of underlying conditions

• Conducted during or directly after initial management of patients
• ECG: specific findings may indicate underlying condition (see above)
• Laboratory
  • Cardiac enzymes
  • Electrolytes
  • TSH
  • Drug levels and toxicology screen
  • Arterial blood gases
• Imaging
  • Coronary angiography
  • Echocardiography
  • Nuclear imaging

• Resuscitation for V-fib
  • Advanced Cardiac Life Support (ACLS)
  • If V-fib does not respond to the standard ACLS protocol (refractory V-fib), consider administration of lidocaine, procainamide, or magnesium
• 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

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

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