Sudden Cardiac Arrest


What Is Sudden Cardiac Arrest (SCA)?

Sudden cardiac arrest (SCA) is an electrical disturbance in the heart that prevents it from beating properly. During SCA, the ventricles flutter in a phenomenon known as ventricular fibrillation, making them unable to deliver blood to the body. The heart responds by quivering, rather than beating in a normal fashion. Blood flow to the brain is reduced to the point that the person loses consciousness and collapses. Unless emergency treatment is provided quickly, the victim's chance of survival is low.

What Are the Symptoms of Sudden Cardiac Arrest?

Symptoms of sudden cardiac arrest typically arrive without warning and are notably strong. The most common symptoms include:

  • Irregular heartbeat
  • Loss of consciousness
  • No pulse
  • Shortness of breath
  • Sudden collapse
  • Weakness
  • Chest discomfort
  • Heart palpitations (fluttering or fast-beating heart)

What Causes Sudden Cardiac Arrest?

Sudden cardiac arrest is caused by a change in the heart’s electrical activity. SCA often affects those who have experienced previous episodes of cardiac arrest, heart attacks, or heart failure; but it can also strike someone with no history of heart problems. Though extremely rare, a sudden blow to the chest can also cause SCA. The condition, known as commotio cordis, can occur when a hard object strikes the chest (directly over the heart) at critical time during a heartbeat.

According to the Heart Rhythm Society, sudden cardiac arrest is a leading cause of death in the United States, accounting for an estimated 350,000 deaths each year.

What Are the Risk Factors of Sudden Cardiac Arrest?

Though sudden cardiac arrest can strike healthy people of any age who are seemingly not at risk, there are a number of risk factors that can contribute to the likelihood of suffering SCA. Fortunately, many of these can be mitigated by lifestyle changes.

The most common risk factors include:

  • Age
  • Being male
  • Chronic kidney disease
  • Diabetes
  • Family history of coronary artery disease
  • Family history of heart disease or disorders
  • High blood cholesterol
  • High blood pressure
  • History of a heart attack
  • History of cardiac arrest within your family
  • Inactive lifestyle
  • Obesity
  • Poor nutrition
  • Sleep apnea
  • Smoking
  • Use of illegal drugs

How Is Sudden Cardiac Arrest Diagnosed?

Following a sudden cardiac arrest and after a patient is stabilized, a hospital can perform a number of tests to diagnose SCA after it has occurred.

ECG (Electrocardiogram)

An electrocardiogram, or ECG, checks the heart’s electrical activity through the use of sensors (called electrodes) placed around the body, typically on the chest. This test measures heart rate and can show important changes in heartbeat that can indicate cardiac arrest.

Imaging Tests

Heart imaging test like X-rays, nuclear scans, coronary catheterization, and echocardiograms use sound waves or other means to create images that can show heart damage and reveal blood flow issues.

Blood Tests

Blood tests can reveal the presence and levels of proteins and hormones that can be indictive of a sudden cardiac arrest.

How to Treat Sudden Cardiac Arrest:

Sudden cardiac arrest must be treated immediately. Treatment involves restoring the heart to its normal beating pattern and must begin with high-quality CPR. Rapid defibrillation is also crucial.

High-quality CPR

With quick action, bystanders can help avert tragedy by performing high-quality CPR. In their 2020 Guidelines, both the American Heart Association and the European Resuscitation Council (ERC) identified five critical components required for providing high-quality CPR:

  • Achieving a rate of 100–120 compressions per minute
  • Compressing the chest to a depth of 2–2.4 inches (5–6 centimeters)
  • Avoiding leaning on the chest to allow for full chest wall recoil after each compression
  • Minimizing pauses in compressions
  • Avoiding excessive ventilation by maintaining 2 breaths to every 30 compressions without advanced airway or 10 breaths per minute with advanced airway


While CPR keeps oxygenated blood flowing to vital organs, only defibrillation can correct certain types of cardiac rhythms. Through the use of an electric shock, defibrillation can get a heart beating normally again. An automated external defibrillator, or AED, can provide a lifesaving shock to an SCA victim. And because SCA can happen anywhere, it’s critically important that AEDs are widely available and accessible to the public. With an AED, anyone can help save a life.

Chain of Survival

The Chain of Survival is a series of steps (or “links”) that can help more people survive sudden cardiac arrest. If a layperson witnesses SCA, they should follow these six links of the Chain of Survival:

  • Activation of the emergency response system
  • Immediate high-quality CPR
  • Rapid defibrillation
  • Basic and advanced emergency medical services
  • Advanced life support and post-arrest care
  • Recovery

How Common Is Sudden Cardiac Arrest?

According to the American Heart Association, sudden cardiac arrest claims the lives of over 430,000 people a year in the U.S., with over 350,000 of these occurring outside the hospital. Survival rates decrease 7 to 10% for each passing minute after SCA if no CPR is provided. However, with the benefit of high-quality CPR and an AED, an SCA victim’s chance of survival can improve dramatically.

How to Reduce the Risk of Sudden Cardiac Arrest

While sudden cardiac arrest can strike without warning, there are a number ways to reduce risk factors that can contribute to the likelihood of suffering SCA.

Regular Follow-up Appointments with Your Doctor

Regular appointments with your doctor can reveal preliminary signs of risk factors that may contribute to the likelihood of sudden cardiac arrest. By regularly visiting your doctor, you can identify and manage these risks before they become more serious problems.

Leading a Healthy Lifestyle

A healthy lifestyle can mitigate many risk factors that may contribute to the likelihood of sudden cardiac arrest. Risk factors like high-blood pressure and high cholesterol, obesity, poor nutrition, and smoking can be reduced or eliminated through lifestyle changes like increasing physical activity and dietary changes.

Genetic Testing

Certain genetic disorders and abnormalities can increase one’s risk of sudden cardiac arrest. A doctor may recommend genetic testing to detect these genetic indicators.

Implantable Cardioverter Defibrillators (ICD)

For those at severe risk of sudden cardiac arrest, doctors may recommend an implantable cardioverter defibrillator (ICD). This small, battery-powered device is implanted within the chest to continuously monitor a patient’s heartbeat and deliver an electric shock when necessary.

Every Minute Counts

Medical attention must be administered as soon as possible after the victim collapses; the chances for survival decrease 7 to 10% with every minute without intervention. Many SCAs occur outside of the hospital, which is why public access AEDs have the potential to help save the lives of countless loved ones struck by cardiac arrest.


Chain of Survival
CPR Overview
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