Ventricular Fibrillation

Ventricular fibrillation (VF) is chaotic ventricular electrical activity with no effective cardiac output, causing cardiac arrest.

Principal cause of sudden cardiac death. Incidence of out of hospital cardiac arrest about 55 per 100,000 per year; shockable rhythm (VF or pulseless VT) in 20 to 30% of arrests.

Causes: acute myocardial ischaemia or infarction (commonest), cardiomyopathy and scar, channelopathies (long QT syndrome, Brugada, short QT, catecholaminergic polymorphic VT), pre excited atrial fibrillation, hypokalaemia, hypomagnesaemia, drug toxicity, electrocution, commotio cordis, hypothermia, hypoxia, subarachnoid haemorrhage.

Idiopathic VF in structurally normal hearts (early repolarisation pattern).

Survival falls by 7 to 10% per minute without defibrillation; survival to discharge about 10% overall, 30 to 50% with immediate bystander CPR and defibrillation.

• Sudden collapse, loss of consciousness, absent pulse, absent breathing or agonal gasps, seizure-like movements, cyanosis.
• Premonitory chest pain, palpitations or syncope in some.
• ECG shows irregular, chaotic undulations with no discernible QRS (coarse or fine).

• Rhythm recognition on defibrillator or monitor during arrest.
• After return of spontaneous circulation: 12 lead ECG (ST elevation, long QT, Brugada pattern, early repolarisation, pre excitation), troponin, electrolytes, magnesium, blood gas, lactate, toxicology.
• Emergency coronary angiography for ST elevation or suspected ischaemic cause.
• Echocardiography, cardiac MRI, CT, genetic testing, and electrophysiology evaluation for cause.
• Family history, drug history, exercise testing, ajmaline challenge as indicated.

Resuscitation

• Immediate high quality CPR (100 to 120 compressions per minute, depth 5 to 6 cm) and early defibrillation: single shock 120 to 200 J biphasic (or maximum energy), immediately resume CPR for 2 minutes.
• Epinephrine 1 mg IV every 3 to 5 minutes after the second shock; amiodarone 300 mg IV after the third shock, then 150 mg (or lidocaine 1 to 1.5 mg/kg). Magnesium sulphate 2 g IV for torsades. Correct reversible causes (4 H and 4 T).
• Refractory VF: double sequential defibrillation, vector change, extracorporeal CPR in selected patients, esmolol 500 micrograms/kg bolus then 50 to 100 micrograms/kg/min.

Post arrest care

• Airway and ventilation (oxygen saturation 92 to 98%, PaCO2 35 to 45 mmHg), mean arterial pressure 65 mmHg or higher, glucose control.
• Targeted temperature management (32 to 36 degrees Celsius) for 24 hours in comatose patients, avoiding fever for 72 hours.
• Emergency coronary angiography for suspected ischaemia.
• Multimodal neuroprognostication after at least 72 hours.

Prevention of recurrence

• ICD for survivors without a reversible cause. Beta blockers (nadolol 1 to 2 mg/kg in channelopathies), amiodarone, quinidine (Brugada, early repolarisation), flecainide (catecholaminergic polymorphic VT), left cardiac sympathetic denervation, ablation of triggers.
• Genetic counselling and cascade family screening.
• Public access defibrillators and CPR training.