Sudden Cardiac Arrest (SCA) is a condition in which the heart stops beating suddenly and unexpectedly due to a malfunction in the heart’s electrical system. The malfunction that causes SCA is a life-threatening abnormal rhythm; an arrhythmia. The most common arrhythmia is Ventricular Fibrillation (VF).
When in VF, the heart’s rhythm is so chaotic (called “fibrillating”) that the heart merely quivers and is unable to pump blood to the body and brain. Once a heart has entered VF, an SCA may occur. During SCA a victim first loses his or her pulse, then consciousness and finally the ability to breathe. All of this can happen quickly – in fact, in a matter of seconds...
Sudden Cardiac Arrest strikes without warning. It does not discriminate and claims hundreds of thousands of lives around the world each year. In the UK alone 250 people die each day irrespective of age, social background and fitness. The vast majority do not survive. By the time you finished reading this page another person would have died! For more information click here.
An Automated External Defibrillator (AED) is an emergency life-saving device for use in the event of Sudden Cardiac Arrest. It is a portable appliance that analyses the heart rhythm and, if needed, administers an electrical charge to the heart in order to establish a regular heartbeat in the event of a Cardiac Arrest.
Only within the first few minutes following a Cardiac Arrest will a victim be in a ‘shockable rhythm’, and therefore rapid defibrillation is vital. Placing AEDs in the community can dramatically reduce the time from collapse to defibrillation and can greatly improve survival rates.
When turned on, the AED will instruct the users to connect the pads to a patient’s bare chest. The pads enable the AED to examine the patient’s heart and determine if the patient is in a viable, shockable rhythm. If the device determines that a shock is required, it will charge up in preparation to deliver a shock. The AED is very safe as it will only deliver a charge when it determines a shockable rhythm is present. For more information click here.
When charged, the device instructs the user to ensure no-one is touching the victim and then to press a button to deliver the shock. In the case of a fully automatic AED the unit will advise the user that it will deliver the shock without further intervention. After the shock is delivered, the device will instruct the user to commence/continue CPR (Cardio Pulmonary Resuscitation) for a period, after which it will analyse the patient’s heart rhythm once again, advising whether a further shock or more CPR is needed.
An AED has an internal memory, which stores the ECG of the patient along with details of the time the unit was activated and the number and strength of any shocks delivered. All this memorised data can be either downloaded to a computer or printed out, so that it can be analysed by appropriate medical personnel.
Using an AED is as simple as 1…2…3
It is the view of the Resuscitation Council (UK) that the use of an AED is NOT to be restricted to trained personnel. However chances of survival increase if the person has had some training in its use. For this reason, it is recommended to run public awareness sessions and training when placing an AED in the community.
AEDs have visual prompts and voice prompts which guide the resuscitator through the process of defibrillation. The device is failsafe and will not administer a shock unless a particular heartbeat is detected.
What is the "Chain of Survival"?
The "Chain of Survival" represents the sequence of events/links that must occur quickly to give the patient the optimum chance of surviving a Sudden Cardiac Arrest. Time is critical - you only have a matter of minutes to restart the heart.
Patients who survive a SCA or who are diagnosed as being at risk of SCA can be treated in a number of ways. Many will be implanted with an ICD, a device like a pacemaker which is placed beneath the skin (usually on the upper chest wall) and has wires connecting it to the heart. This device constantly monitors the heart and will deliver a shock to defibrillate the heart if needed. Being fully implanted and completely automatic, the patient is able to lead a normal life with few limitations, safe in the knowledge that the ICD will respond immediately if required. Some patients may only need to take medication alone or in addition to an ICD. Occasionally some causes of SCA (such as WPW) can be treated by a curative procedure whereby the additional wiring is destroyed by a small burn inside the heart, using a technique known as ‘Catheter Ablation’.
All patients who have survived a SCA should be reviewed by a cardiac electrophysiologist (a specialist in heart rhythm disturbances) in order to determine how best to prevent further events and to consider whether family members need to be screened.
Quick action by the first person on scene can truly make a difference in saving a life.