Refractory Ventricular Fibrillation

Refractory ventricular fibrillation (shock refractory ventricular fibrillation or pulseless ventricular tachycardia) is ventricular fibrillation that persists after three consecutive shocks, together with high quality cardiopulmonary resuscitation, adrenaline and amiodarone. Recurrent ventricular fibrillation after temporary return of rhythm is called electrical storm in the peri-arrest setting.

Epidemiology. A shockable first rhythm is found in 20 to 30% of out-of-hospital cardiac arrests. About 1 in 5 of those patients remain in ventricular fibrillation after three shocks, and survival falls by about 5 to 10% with each minute of delay.

Causes and associations. Acute coronary occlusion, cardiomyopathy, prior myocardial scar, channelopathy (Brugada, long QT, short QT), electrolyte disturbance, drug toxicity, hypothermia, commotio cordis, pulmonary embolism, tamponade and tension pneumothorax.

Pathophysiology. Multiple re-entrant wavelets cause disorganised ventricular activity. Persistent ischaemia, catecholamine surge, acidosis and myocardial stunning make the heart refractory to defibrillation. Pro arrhythmic substrate persists after shock.

Presentation is collapse with absent pulse and a coarse or fine chaotic rhythm on the monitor. Fine ventricular fibrillation may be mistaken for asystole.

Red flags.

• Fibrillation persisting after three or more shocks.
• Witnessed arrest, young patient or known channelopathy, which favours reversible causes and mechanical support.

Diagnosis is by ECG rhythm. Check pad position and contact, signal quality and leads. Search for reversible causes (hypoxia, hypovolaemia, hypo- or hyperkalaemia, hypothermia, hydrogen ion excess, toxins, tamponade, tension pneumothorax and thrombosis) with ultrasound during rhythm checks. Check gas, potassium, magnesium and calcium. After return of circulation, do a 12-lead ECG and coronary angiography as indicated.

Differential diagnosis. Fine ventricular fibrillation mistaken for asystole, torsades de pointes, artefact and polymorphic ventricular tachycardia.

High quality resuscitation. Compress to a depth of 5 to 6 cm at 100 to 120 compressions/min with full recoil, minimise pauses (shock within 5 seconds), and change the compressor every 2 minutes. Give oxygen and secure access (IV or intraosseous).

Defibrillation.

• Biphasic shock of 150 to 200 J for each shock (escalate to the maximum available if the device allows), repeated every 2 minutes.
• Check pad position (anterior lateral), try anterior posterior placement, and change the vector after three failed shocks. Double sequential defibrillation (two defibrillators with near simultaneous shocks) is an option with limited evidence in a few settings.

Drugs.

• Adrenaline 1 mg IV or intraosseous after the third shock, then every 3 to 5 minutes.
• Amiodarone 300 mg IV or intraosseous after the third shock, then 150 mg after the fifth shock. Alternatively lidocaine 1 to 1.5 mg/kg IV (then 0.5 to 0.75 mg/kg, to a total of 3 mg/kg), preferred in cases of long QT or when amiodarone is unavailable.
• Magnesium sulphate 2 g IV over 1 to 2 minutes for torsades de pointes or hypomagnesaemia.
• Calcium chloride 10% 10 mL IV for hyperkalaemia, hypocalcaemia or calcium blocker toxicity.
• Esmolol 500 microgram/kg IV bolus then 50 to 100 microgram/kg/min has been used in refractory ventricular fibrillation with limited evidence.

Reversible causes. Treat each, with ultrasound to detect tamponade and pneumothorax, thrombolysis (alteplase 50 mg IV bolus) for suspected pulmonary embolism, and rewarming for hypothermia.

Extracorporeal CPR. Early extracorporeal membrane oxygenation in selected patients with witnessed arrest, age under 70 years, short low flow time (under 60 minutes) and a potentially reversible cause, in centres able to do it.

Coronary angiography. For ST elevation or suspected coronary cause, with percutaneous intervention, even during ongoing resuscitation if mechanical CPR and extracorporeal support are available.

Other measures. Stellate ganglion block and deep sedation are used in electrical storm.

After return of circulation. Post-cardiac arrest care, correction of potassium (4.0 to 5.0 mmol/L) and magnesium (over 1.0 mmol/L), amiodarone infusion 1 mg/min for 6 hours then 0.5 mg/min, and beta blockade if no heart failure or shock.

Monitoring. Rhythm, compressions quality (end tidal carbon dioxide over 2.7 kPa or 20 mmHg), arterial gas and electrolytes.

Referral and escalation. Cardiology and intensive care for extracorporeal support.

Special groups. In hypothermia, limit shocks to three until core temperature is over 30 °C. In pregnancy, manual uterine displacement and consider perimortem caesarean delivery at 4 minutes. In children, 4 J/kg for each shock, adrenaline 10 microgram/kg and amiodarone 5 mg/kg.