A cardiac arrest occurs when the Heart suddenly stops pumping. This may be the result of a number of conditions but is most commonly associated with a heart attack (myocardial infarction).

What does the cardiovascular system do?

The cardiovascular system (CVS) consists of the heart, lungs and blood vessels. It is responsible for transportation of vital nutrients, gases and hormones throughout the body. The heart functions as the central pump with the blood vessels the pipes of the body. The CVS is controlled by a number of internal and external systems, which keep the CVS in balance with the needs of the body.

The heart is a pear shaped organ positioned centrally within the chest cavity with the apex extending over to the left nipple. The heart is a divided into a right and left side, each side has an atrium and ventricle. Heart valves and the contraction of the heart muscle control blood flow through the heart. The right side receives de-oxygenated blood from the major veins of the body and pumps this blood into the lungs. The left side of the heart then receives oxygen rich blood from the lungs and pumps this blood into the Aorta and arteries of the body. This pumping action is a complex well-coordinated activity that cannot be fully explained here. The heart receives its blood supply via the left and right coronary arteries.

Poor or abnormal function of the cardiovascular system

May be a result of:

• Insufficient blood supply due to dehydration, bleeding or swelling;
• A poor blood supply to the heart, where there is not enough oxygen and other nutrients for its work;
• Poor lung function or obstruction to blood flow in the lungs, which places a strain on the heart muscle;
• Too many or too few electrolytes (eg. potassium, magnesium) that cause irregular heartbeats or dangerous rhythms in the heart.
• Weakness of blood vessel walls.
  Heart muscle weakness

Cardiac Arrest-(Heart Attack) Pathophysiology

A cardiac arrest occurs when the Heart suddenly stops pumping. This may be the result of a number of conditions but is most commonly associated with a heart attack (myocardial infarction). Other conditions include a large brain haemorrhage, severe chest trauma, severe multi trauma with a large blood loss, imbalances of body chemicals or heart rhythm irregularities.

When a person suffers a cardiac arrest they become unconscious, they won’t be breathing and there will be no pulse. It is vital that cardiac function be restored as a matter of urgency so that the brain and other vital organs are not starved of oxygen for a prolonged period. Three minutes without oxygen will see the brain cells start to die. The prognosis of a person suffering from a cardiac arrest is linked closely to how long it takes for the Heart to begin pumping again, how well it is pumping and the persons previous medical history. The time from when a person’s heart stops beating to the time it starts beating again is known as ‘down-time’.

General Treatment Options

The first line treatment for a person suffering a cardiac arrest is to make the heart beat again as soon as possible. This means getting emergency care (an ambulance) as soon as possible and performing cardiopulmonary resuscitation (CPR) until the emergency service arrives. In general the emergency services will continue CPR and connect the patient to a defibrillator-monitor and may need to "shock" the patient’s heart. If the emergency services are able to restart the heart they will transport the patient to an emergency department for further management. The Emergency department staff will stabilise the patient who will then be transferred to the most appropriate ward, unit or hospital. This may be a coronary care unit or an intensive care. The ongoing treatment will be linked to the causes and consequences of the cardiac arrest.

What Happens in Intensive Care?

Treatment for a patient who has suffered a cardiac arrest may be straightforward or quite complex depending on the individual patient and their immediate condition post cardiac arrest. Some patients remain unconscious and need intubation and ventilation with a breathing machine. Investigations to identify the cause of the cardiac arrest will be done and treatment started accordingly. You can expect the patient to have frequent chest x-rays and blood tests. Close monitoring of vital signs may be done using an arterial line, oxygen saturation monitor and a bedside monitor. The patient will receive intravenous fluids and have an indwelling urinary catheter and nasogastric tube. Monitoring for the return of brain function is attended at the bedside. Further investigations will be required if the patient does not 'wake up' in a short time.

How long will the patient remain in Intensive Care?

The outcomes from out of hospital cardiac arrests are generally very poor with many people dying before they get to hospital. Patients whose hearts did not start beating again for longer than four minutes (long 'down time') may have suffered an ‘hypoxic’ brain injury. That is their brain was without blood flow and oxygen for too long. If the patient is admitted to the intensive care unit, the doctors will discuss the prognosis of the patient with relatives or carers. The longer the ‘down time’ and the longer the patient remains in a coma the worse the prognosis generally is. A down time of more that 10 minutes, fitting (seizures), abnormal heart rhythms or failure of the patient to 'wake up' within 24 hrs are signs the patient may not recover.

The information contained on this page is general in nature and therefore cannot reflect individual patient variation. In addition it reflects Australian intensive care practice which may differ from other countries. It is meant as a back up to specific information which will be discussed with you by the Doctors and Nurses caring for your loved one. ICCMU attests to the accuracy of the information contained here BUT takes no responsibility for how it may apply to an individual patient. Please refer to the full disclaimer.

Cardiac Arrest Version 1 (Author K Rolls Clinical Project Officer ICCMU)

First Posted December 2004, modified September 2005