What is the management strategy for ventricular fibrillation?

Management of Ventricular Fibrillation

Ventricular fibrillation requires immediate unsynchronized defibrillation with an initial energy of 200J (monophasic) or manufacturer-recommended dose for biphasic defibrillators, followed by immediate resumption of high-quality CPR starting with chest compressions. 1, 2

Immediate Recognition and CPR

• Recognize VF on cardiac monitor as disorganized electrical activity without discernible QRS complexes 2, 3
• Begin high-quality CPR immediately at a rate of at least 100 compressions per minute with a depth of 2/3 of the anteroposterior chest diameter 2, 3
• Minimize interruptions in chest compressions, including during rhythm analysis 2
• Attach a monitor/defibrillator as soon as possible 2

Critical timing consideration: For witnessed VF arrest with immediate defibrillator access, deliver the shock first then begin CPR; however, for unwitnessed arrest or when response time exceeds 5 minutes, consider 2 minutes of CPR before the first shock 2, 4. This distinction is important because patients with ambulance response intervals longer than 5 minutes had significantly better outcomes (22% vs 4% survival to discharge) when CPR was performed for 3 minutes before defibrillation 4.

Defibrillation Protocol

The defibrillation sequence must be unsynchronized (never synchronized for VF): 1, 2, 5

• First shock: 200J (monophasic) or per manufacturer for biphasic 1, 2
• Second shock (if unsuccessful): 200-300J 1, 2
• Third shock (if necessary): 360J 1, 2
• Resume CPR immediately after each shock, beginning with chest compressions 2, 3

Important caveat: Do not delay defibrillation for witnessed VF arrest 2, 5. Chest compressions performed immediately after successful defibrillation can paradoxically cause early VF recurrence, with a 15.5-fold increased hazard of recurrence in the first 2 seconds of CPR compared to before CPR resumption 6. However, current guidelines still recommend immediate CPR resumption because the overall benefit outweighs this risk 2.

Medication Administration

Establish IV/IO access while continuing CPR: 2, 5

• Epinephrine 1mg IV/IO every 3-5 minutes throughout the resuscitation 2, 3, 5
• Amiodarone for refractory VF: 150mg IV infused over 10 minutes, followed by 1.0 mg/min infusion for 6 hours, then 0.5 mg/min maintenance 1, 7
  • Amiodarone is FDA-approved for frequently recurring VF and hemodynamically unstable VT refractory to other therapy 7
  • For breakthrough VF episodes during amiodarone infusion, give supplemental 150mg doses over 10 minutes 7
• Lidocaine 1.5mg/kg IV/IO may be considered if amiodarone is unavailable 2, 5

Evidence strength: Intravenous amiodarone is considered acceptable, safe, and useful based on two randomized clinical trials for shock-resistant VF (defined as VF persisting after 3 defibrillation attempts) 8. Approximately 10-25% of cardiac arrests develop shock-resistant VF, with 87-98% mortality 8.

Advanced Airway Management

• Consider advanced airway placement after initial shocks if personnel are available 2, 5
• If an advanced airway is placed, deliver 1 breath every 6 seconds (10 breaths/min) with continuous compressions 2, 5
• Use waveform capnography to confirm and monitor endotracheal tube placement 2, 5
• Avoid excessive ventilation, which decreases cardiac output during CPR 2, 5

Post-Resuscitation Care

After achieving return of spontaneous circulation (ROSC): 3, 5

• Maintain adequate ventilation and oxygenation 2, 5
• Correct electrolyte abnormalities immediately, particularly potassium and magnesium, to prevent recurrent VF episodes 1, 3, 5
• Search for and treat reversible causes (Hs and Ts): Hypovolemia, Hypoxia, Hydrogen ion (acidosis), Hypo/hyperkalemia, Hypothermia, Tension pneumothorax, Tamponade, Toxins, Thrombosis (pulmonary and coronary) 2, 3, 5
• Consider beta-blockers if VF occurred in the context of acute myocardial infarction 3, 5

Temporal context matters: Primary VF is most common (3-5% incidence) in the first 4 hours after myocardial infarction and declines markedly thereafter 1, 3. Primary VF is associated with significantly higher in-hospital mortality, but survivors to discharge have the same long-term prognosis as patients without primary VF 1.

Refractory Ventricular Fibrillation

For drug-refractory polymorphic VT/VF, pursue aggressive ischemia reduction: 1, 5

• Beta-adrenoceptor blockade 1
• Intra-aortic balloon pumping 1
• Emergency PTCA/CABG surgery 1

Emerging therapies (limited evidence): Low-dose esmolol has shown promise in case reports for refractory VF unresponsive to standard ACLS, amiodarone, and double sequential defibrillation 9, 10. Dual sequential defibrillation, vector change defibrillation, and left stellate ganglion block are also being investigated but require further evidence before adoption as standard practice 10.

Special Populations

Wolff-Parkinson-White syndrome with rapid AF: 1, 3

• Immediate electrical cardioversion is mandatory when AF with rapid ventricular response causes hemodynamic instability, as this prevents degeneration to VF 1
• Never administer IV beta-blockers, digitalis, diltiazem, or verapamil in patients with pre-excitation syndromes, as these facilitate conduction through accessory pathways and can precipitate VF 1, 3

Pediatric patients: 2

• First shock: 2 J/kg 2
• Second shock: 4 J/kg 2
• Subsequent shocks: 4-10 J/kg 2

Critical Pitfalls to Avoid

• Never use synchronized cardioversion for VF—always use unsynchronized shocks 1, 2, 5
• Do not treat isolated ventricular premature beats, couplets, accelerated idioventricular rhythm, or nonsustained VT 1, 5
• Avoid excessive interruptions in chest compressions for rhythm checks 2, 5
• Do not administer AV nodal blocking agents (digoxin, diltiazem, verapamil, beta-blockers) in pre-excitation syndromes 1, 3
• Monitor for amiodarone-related hypotension (most common adverse effect, occurring in 16% of patients), which is rate-related rather than dose-related 7
• Use central venous access for amiodarone concentrations >2 mg/mL to avoid peripheral vein phlebitis 7