Cardiac Arrest

This is an abrupt loss of heart function which results in having no effective cardiac output.

The most common cause of cardiac arrest is ischaemic heart disease.

Without an effective cardiac output, this reduces perfusion to critical tissues like the brain and very quickly will lead to irreversible brain death

There are 4 types of rhythm which are associated with a cardiac arrest.

2 of these are shockable, meaning that the person can be defibrillated, whereas the other 2 are classified as non-shockable rhythms.

Causes

There are few reversible causes of cardiac arrest, called the 4 H’s and 4 T’s:

Thrombosis

Toxins

Tamponade

Tension Pneumothorax 

Symptoms

Loss of consciousness

No breathing

No pulse

Cyanosis

Management

Full management of cardiac arrest can be found in the advanced life support (ALS) algorithm. The mainstay of management is summarised by below:

1) Assess for signs of life – if no signs of life, then start CPR (ratio of chest compressions to ventilation is 30:2)

2) Connect defibrillator and assess cardiac rhythm

If shockable rhythm

Deliver 1st shock, followed by 2 minutes CPR. Re-assess rhythm.

If still shockable, deliver next shock, followed by 2 minutes CPR and rhythm check

This can be repeated until return of spontaneous circulation or until decision to stop

After the 3rd shock, give IV adrenaline 1 mg and then again after every 3–5 minutes

After the 3rd shock you can also give IV amiodarone

If non-shockable rhythm

Start CPR immediately (ratio of chest compressions to ventilation is 30:2)

Give 1 mg IV adrenaline as soon as IV access is achieved (and repeat after 3–5 minutes)

After 2 minutes CPR, re-assess rhythm

Aim is to achieve return of spontaneous circulation or convert to shockable rhythms

Shockable Rhythms

Pulseless Ventricular Tachycardia (VT)

This is a broad complex tachycardia with a ventricular rate > 100 bpm.

Although this rhythm can produce a cardiac output, if the patient does not have a pulse, this patient is in full cardiac arrest.

ECG features

Atrial rhythm/rate can’t be determined.

Rhythm regular and rapid >100bpm.

QRS is wide (> 0.12 s) and increased amplitude 

Ventricular fibrillation (VF)

This is a chaotic pattern of electrical impulses in the ventricles, producing no effective contraction.

The ventricles quiver instead of contract, compromising cardiac output.

It is the most common cause of sudden cardiac death.

ECG features

Ventricular activity has no recognizable pattern

Non Shockable Rhythms

Asystole

This is where the heart completely stops beating with no activity.

It usually follows bradycardias such as heart block.

ECG features

Flat line on ECG with no QRS complexes

Pulseless electrical activity (PEA)

This is a state where the monitor shows electrical activity in the heart, but the patient will have no palpable pulse and so is in cardiac arrest.

ECG features

Irregular activity (can look quite normal) on the ECG

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