A cardiac arrest is the cessation of normal circulation of the blood due to failure of the ventricles of the heart to contract effectively during systole. The resulting lack of blood supply results in cell death from oxygen starvation. Cerebral hypoxia, or lack of oxygen supply to the brain, causes victims to immediately lose consciousness and stop breathing.

Cardiac arrest is a medical emergency that, if left untreated, invariably leads to death within minutes. The primary first-aid treatment for cardiac arrest is cardiopulmonary resuscitation.

Etiology

Coronary artery disease (CAD) is the predominant disease process associated with sudden cardiac death in the United States. The incidence of CAD in individuals who suffer sudden cardiac death is between 64 and 90%.

Causes

In apparently healthy adults, cardiac arrest is often caused by ventricular fibrillation during myocardial infarction (heart attack).

In children, cardiac arrest is typically caused by hypoxia from other causes such as near-drowning. With prompt treatment survival rates are high.

Every fatal injury or illness ultimately terminates in cardiac arrest, which is a natural part of the processes of death.

Diagnosis

The state of cardiac arrest is diagnosed in an unconscious (unresponsive to vigorous stimulation) person who does not have a pulse.

An ECG clarifies the exact diagnosis and guides treatment. but treatment should begin without awaiting an ECG. The ECG may reveal:

• asystole (known colloquially as a flatline),
• ventricular fibrillation,
• ventricular tachycardia
• severe bradycardia,
• complete heart block with a slow ventricular escape rate
• or even normal electrical activity (pulseless electrical activity, formerly called electromechanical dissociation).

Potentially treatable causes of pulseless electrical activity and some other arrhythmias include:

• cardiac tamponade
• tension pneumothorax
• toxins or drug overdoses
• thromboembolism or other mechanical obstruction
• lack of oxygen (hypoxia)
• potassium disturbance (hypokalemia or hyperkalemia)
• hypocalcaemia
• acidaemia
• decreased blood volume (hypovolemia) due to haemorrhage or dehydration
• hypothermia

Treatment

First aid

Seconds count. Call for help immediately or send someone for help. Begin cardiopulmonary resuscitation (CPR) immediately. CPR only buys time for advanced responders to arrive and does not restart the heart. If an automated external defibrillator is available, use it at once.

Field care

Appropriately trained personnel apply advanced cardiac life support protocols as soon as they arrive, unless there is a valid do not resuscitate order or advance health directive. If so, it is ethically appropriate to permit natural death to occur in accordance with the wishes of the patient.

Hospital treatment

In many hospitals, cardiac arrest results in one of the carers announcing a "Code Blue" for immediate response by a trained team of nurses and doctors. The resuscitating team continues advanced cardiac life support until the patient recovers or a doctor declares the patients death.

Ethical Issues

Cardiopulmonary resuscitation and advanced cardiac life support are not always in a persons best interest. This is particularly during terminal illness when resuscitation will not alter the outcome of the disease. Properly performed CPR often fractures the rib cage. Defibrillation, especially repeated several times as called for by ACLS protocols, may also cause electrical burns. Internal cardiac massage, an ACLS procedure performed by emergency medicine physicians in requires splitting open the rib cage, which is painful during the weeks of recovery. While such treatment is worthwhile when it saves a life, it is undignified and simply adds to the suffering of a victim with a terminal illness who wishes to die peacefully.

It is not surprising that most people with a terminal illness choose to avoid such "heroic" measures and die peacefully.

People with views on the treatment they wish to receive in event of a cardiac arrest to should discuss these views with both their doctor and with their family.

It is also important that these views are written down somewhere in the medical record. In the event of cardiac arrest, health professionals need to act quickly on the information that is available to them. As cardiac arrest often happens out of regular hours, the resuscitation team rarely includes anybody who actually knows the patient.

A patient may ask their doctor to record a do not resuscitate (DNR) order in the medical record. Alternatively, in many jurisdictions, a person may formally state their wishes in an "advance directive" or "advance health directive".

See also death and hospice.