Chain of Survival
About thirty years ago, it was discovered that if a series of events took place, in a set sequence, a patient suffering from a heart attack stood a greater chance of survival. These events are now known as the 'Chain of Survival'.
The First Link
When Sudden Cardiac Arrest strikes, an immediate 999 call is crucial; a delay of just a few minutes could prove fatal. By quickly recognizing a medical emergency, a bystander can help save a life.
Could you recognize the symptoms of Sudden Cardiac Arrest?
Unresponsiveness
Loss of consciousness
Lack of pulse
Cessation of breathing
Sudden Cardiac Arrest is not the same as a heart attack. However, a victim of either condition requires an immediate 999 call.
The Second Link
CPR or Cardiopulmonary resuscitation is the second link in the Chain of Survival; it is the link that can buy life-saving time between the first link (Early Access to Emergency Care) and the third link (Early Defibrillation).
During Sudden Cardiac Arrest (SCA), the heart twitches irregularly most often due to ventricular fibrillation (VF) and cannot pump oxygenated blood efficiently to the brain, lungs, and other organs. The victim quickly stops breathing and loses consciousness.
However, prompt CPR can help sustain life during VF. The mouth-to-mouth breathing and chest compressions help oxygenated blood flow to the person's brain and heart, until defibrillation can attempt to restore normal heart pumping.
Studies have shown that chest compression-only CPR may be as effective as combined ventilation and compression in the first few minutes after a non-asphyxial arrest. Lay people should, therefore, be encouraged to do compression-only CPR if they are unable or unwilling to provide rescue breaths, although combined chest compression and ventilation is the better method of CPR.
The Third Link
Although it is an important link in the Chain of Survival, CPR alone cannot fully resuscitate a person in SCA. Early defibrillation is the third and perhaps most significant link. Most SCA victims are in ventricular fibrillation (VF), an electrical malfunction of the heart that causes the heart to twitch irregularly. Defibrillation, the delivery of an electrical shock to the heart muscle, can restore normal heart function if it occurs within minutes of SCA onset.
When CPR and defibrillation are provided within eight minutes of an episode, a person's chance of survival increases to 20%.
When these steps are provided within four minutes and a paramedic arrives within eight minutes, the likelihood of survival increases to over 40%.
The Fourth Link
The fourth link in the Chain of Survival is advanced care. Paramedics and other highly trained EMS (Emergency Medical Services) personnel provide this care, which can include basic life support, defibrillation, administration of cardiac drugs, and the insertion of endotracheal breathing tubes. This type of advanced care can help the heart in VF respond to defibrillation and maintain a normal rhythm after successful defibrillation.
The trained EMS personnel monitor the patient closely on the way to the hospital, where more definitive diagnostic evaluation can occur.
| Time After the Onset of Attack | Survival Chances |
|---|---|
| With every minute | Chances are reduced by 7-10% |
| Within 4-6 minutes | Brain damage and permanent death start to occur |
| After 10 minutes | Few attempts at resuscitation succeed |
| Type of Care for SCA Victims after Collapse | Chance of Survival |
|---|---|
| No care after collapse | 0% |
| No CPR and delayed defibrillation (after 10 minutes) | 0-2% |
| CPR from a non-medical person (such as a bystander or family member) begun within 2 minutes, but delayed defibrillation | 2-8% |
| CPR and defibrillation within 8 minutes | 20% |
| CPR and defibrillation within 4 minutes; paramedic help within 8 minutes | 43% |
Since more than 70% of SCA cases occur at home, and another 10% to 15% occur at work, trained EMS personnel are unlikely to be at the scene at onset. Therefore, trained lay responders with quick access to defibrillation units can be a vital asset when SCA strikes. In certain environments, where the Chain is strong and when defibrillation occurs within the first few minutes of cardiac arrest, survival rates can approach 80% to 100%.
People who survive sudden cardiac arrest have an excellent prognosis: 83% survive for at least one year, and 57% survive for five years or longer. In fact, when analyzed by age group, survival rates for SCA survivors are comparable to survival rates of people who have never had an event. Clearly, early intervention can offer years of productivity and fulfillment to victims of SCA.
