Tachyarrhythmias
Ventricular fibrillation
Chaotic, irregular deflections with no identifiable complexes — a shockable cardiac arrest rhythm.
What you see
- Irregular deflections of varying amplitude and frequency.
- No recognisable P waves, QRS complexes or T waves.
- Coarse VF early, degenerating to fine VF and then asystole.
Why it looks like that
Multiple wandering re-entrant wavelets depolarise the ventricles without any coordinated contraction. There is no cardiac output from the moment it starts.
What to do
- Immediate unsynchronised defibrillation, then two minutes of CPR before reassessing.
- Adrenaline 1 mg after the third shock and every 3–5 minutes thereafter; amiodarone 300 mg after the third shock.
- Treat reversible causes — the four Hs and four Ts.
- Targeted temperature management and coronary angiography after return of circulation.
The trap
Artefact from movement, shivering or a disconnected lead can mimic VF perfectly. Look at the patient before you look at the monitor: if there is a palpable pulse, no shock is warranted, however convincing the trace.
More in tachyarrhythmias
Atrial fibrillation
Irregularly irregular narrow complexes with no P waves and a wandering baseline.
Atrial flutter
Sawtooth flutter waves at about 300 per minute, usually conducted 2:1 to give a ventricular rate near 150.
AV nodal re-entrant tachycardia
Regular narrow complex tachycardia around 180 with P waves hidden inside or just after the QRS.
Monomorphic ventricular tachycardia
Broad, regular, identical complexes — assume VT in any broad complex tachycardia until you have proved otherwise.