Sudden Cardiac Arrest

Sudden cardiac arrest (SCA) is the natural death from cardiac causes, heralded by abrupt loss of consciousness within one hour of the onset of acute symptoms. This usually happens when the heart stops beating unexpectedly, and oxygen-rich blood is unable to reach the brain, lungs, and other organs.

Sudden cardiac arrest is different from a heart attack

A heart attack occurs when blood flow to the heart is blocked, resulting in the death of parts of the heart muscle.

Cardiac arrest occurs when the heart malfunctions and stops beating unexpectedly. It is one of the complications of a heart attack. In fact, about half of heart attack victims present with SCA.

The immediate cause of SCA is often a sudden development of an abnormal heart rhythm called ventricular fibrillation (VF) or less commonly due to asystole (heart stops contracting). In VF, there is chaotic electrical activity without mechanical contraction so that there is a rapid cessation of blood circulation. VF can be preceded by ventricular tachycardia (VT) with a rapid heart rate, e.g. 200 beats per minute, but very low blood pressure.

When the pumping action is disrupted, the heart cannot pump blood to the brain, lungs and other organs. Seconds later, a person becomes unresponsive and stops breathing (or gasps for air). Death occurs within minutes if the victim does not receive treatment immediately.

Signs

Sudden cardiac arrest can be preceded by the classic symptoms of a heart attack, which then rapidly progress into:

• Loss of consciousness
• Fits (convulsion)
• Gasping
• No breathing

Causes

• Coronary heart disease

  About 80% of sudden cardiac arrest is due to coronary heart disease (CHD). Since CHD is a condition that increases with age, sudden cardiac arrest is also more likely to be due to CHD in older patients.

  SCA is particularly likely to occur more severely with CHD when more coronary arteries are affected and when the main trunk of the left coronary artery is obstructed (sometimes called the “widow maker’s disease).

  SCA risk is also higher in those who previously had a heart attack resulting in extensive heart muscle damage and heart failure.

  Since CHD is the most common underlying cause of SCA, the risk factors would be those that cause atherosclerosis, the disease process of CHD. These include age, smoking, high blood pressure, high cholesterol, diabetes, obesity, sedentary lifestyle, stress and family history.

• Genetics

  In younger patients in whom CHD is less frequent, other causes arising from genetics may be present. These conditions include:
  • Abnormalities of the electrical system of the heart e.g. the “long QT interval syndromes”
  • Brugada syndrome
  • Abnormalities of the heart muscle e.g. hypertrophic cardiomyopathy
  • Various forms of congenital heart disease (“hole-in-the-heart”, “blue babies”)
  • Various heart valve disease

Prevention

The risk of sudden cardiac arrest can be reduced by reducing the risk of CHD.

• Screening and effective control of CHD risk factors e.g. high blood pressure, high cholesterol, etc.
• In those with known CHD, various types of tests can be conducted to identify those at higher risk of heart attack and SCA.
  These tests include ECG, exercise or other types of stress tests, echocardiography, imaging techniques e.g. CT scans, isotope scans, coronary angiography, ECG Holter Monitoring and electrophysiologic study.
• Those at higher risk may be treated with medications, angioplasty, pacemakers or implantable defibrillators.

In younger individuals those with a family history of SCA or other types of heart disease affecting younger family members may be screened by a doctor and referred if there are suggestive signs e.g. an abnormal ECG.

Individuals planning to participate in strenuous exercise should have a medical examination, including an ECG, a stress test (e.g. a treadmill test), and other types of cardiac examination.

Treatment

What should you do when someone is having a sudden cardiac arrest?

The essential steps for helping a cardiac arrest victim are illustrated in a system called the “Chain of Survival”. The seven rings in this chain are:

Do your part by completing the first four rings of the chain.
First Ring: Prevention
Prevention is better than intervention. A healthy diet and lifestyle can reduce the risk of heart diseases. Going for regular medical check-ups can help detect problems early and prompt the individuals to seek treatment early and adjust their diet and lifestyles.

Second Ring: Early Activation and AED Access
Call 995 for an ambulance and ask someone to get an AED. Follow the SCDF dispatcher’s instructions.

Third Ring: Early CPR
Initiate CPR as soon as possible to provide oxygen and blood flow to the brain and heart.

Fourth Ring: Early Defibrillation
If two people are available to help, one should begin CPR immediately while the other calls 995 and finds an AED.

AEDs are increasingly available in the community, at lift lobbies, shopping malls, and schools. Download the myResponder app, and it will show the AED nearest to you.

Follow the voice prompts from the AED and be ready to defibrillate.

Fifth Ring: Emergency Medical Services (Ambulance)

Quick access to the scene and transport to the hospital makes a difference to the chance of survival for the casualty.

Life-threatening cases, such as cardiac arrests, are critically time-sensitive and will receive enhanced medical support and a faster response from the Singapore Civil Defence Force (SCDF). In addition to sending an ambulance and a fire bike, SCDF will also deploy Emergency Medical Technicians (EMTs) on red rhino, fire-engine or fire medical vehicles to render prompt medical treatment and perform concerted high-performance CPR on victims.

The team will focus on performing quality and continuous chest compressions with controlled ventilation, which will greatly improve the chances of the victim’s survival.

Sixth Ring: Early Advanced Care

Medical teams will provide advanced cardiac life support at the hospital with the use of Intravenous/Intraosseous (IV/IO) medication and delivery of oxygen via mechanical systems (i.e., Bag-Valve Masks and ventilators).

Seventh Ring: Recovery
To ensure a good survival outcome after OHCA, requires continued community and medical support (i.e., social services, physio/occupational therapy, nutritional guidace, etc) and therapy to rehabilitate the individual back to normalcy.