about sudden cardiac arrest and its prevention

Sudden cardiac arrest (SCA) is a condition in which the heart suddenly and unexpectedly stops beating. If this happens, blood stops flowing to the brain and other vital organs.

SCA usually causes death if it’s not treated within minutes.

Overview

To understand SCA, it helps to understand how the heart works. The heart has an electrical system that controls the rate and rhythm of the heartbeat. Problems with the heart’s electrical system can cause irregular heartbeats called arrhythmias.

There are many types of arrhythmias. During an arrhythmia, the heart can beat too fast, too slow, or with an irregular rhythm. Some arrhythmias can cause the heart to stop pumping blood to the body—these arrhythmias cause SCA.

SCA is not the same as a heart attack. A heart attack occurs if blood flow to part of the heart muscle is blocked. During a heart attack, the heart usually doesn’t suddenly stop beating. SCA, however, may happen after or during recovery from a heart attack.

People who have heart disease are at higher risk for SCA. However, SCA can happen in people who appear healthy and have no known heart disease or other risk factors for SCA.

symptoms:

Sudden cardiac arrest symptoms are immediate and drastic.

• Sudden collapse
• No pulse
• No breathing
• Loss of consciousness

Sometimes other signs and symptoms precede sudden cardiac arrest. These may include fatigue, fainting, blackouts, dizziness, chest pain, shortness of breath, weakness, palpitations or vomiting. But sudden cardiac arrest often occurs with no warning.

When to see a doctor

If you have frequent episodes of chest pain or discomfort, heart palpitations, irregular or rapid heartbeats, unexplained wheezing or shortness of breath, or fainting or near fainting or you’re feeling lightheaded or dizzy, see your doctor promptly. If these symptoms are ongoing, you should call 911 or emergency medical help.

When the heart stops, the lack of oxygenated blood can cause brain damage in only a few minutes. Death or permanent brain damage can occur within four to six minutes. Time is critical when you’re helping an unconscious person who isn’t breathing. Take immediate action.

• Call 911, or the emergency number in your area, if you encounter someone who has collapsed or is found unresponsive. If the unconscious person is a child and you’re alone, administer CPR, or chest compressions only, for two minutes before calling 911 or emergency medical help or before using a portable defibrillator.
• Perform CPR. Quickly check the unconscious person’s breathing. If he or she isn’t breathing normally, begin CPR. Push hard and fast on the person’s chest — about 100 compressions a minute. If you’ve been trained in CPR, check the person’s airway and deliver rescue breaths after every 30 compressions. If you haven’t been trained, just continue chest compressions. Allow the chest to rise completely between compressions. Keep doing this until a portable defibrillator is available or emergency personnel arrive.
• Use a portable defibrillator, if one is available. If you’re not trained to use a portable defibrillator, a 911 or emergency medical help operator may be able to guide you in its use. Deliver one shock if advised by the device and then immediately begin CPR starting with chest compressions, or give chest compressions only, for about two minutes. Using the defibrillator, check the person’s heart rhythm. If necessary, the defibrillator will administer a shock. Repeat this cycle until the person recovers consciousness or emergency personnel take over.

Portable automated external defibrillators (AEDs) are available in an increasing number of places, including airports, casinos and shopping malls. You can also purchase them for your home. AEDs come with built-in instructions for their use. They’re programmed to allow a shock only when appropriate.

What Causes Sudden Cardiac Arrest?

Ventricular fibrillation (v-fib) causes most sudden cardiac arrests (SCAs). V-fib is a type of arrhythmia.

During v-fib, the ventricles (the heart’s lower chambers) don’t beat normally. Instead, they quiver very rapidly and irregularly. When this happens, the heart pumps little or no blood to the body. V-fib is fatal if not treated within a few minutes.

Other problems with the heart’s electrical system also can cause SCA. For example, SCA can occur if the rate of the heart’s electrical signals becomes very slow and stops. SCA also can occur if the heart muscle doesn’t respond to the heart’s electrical signals.

Certain diseases and conditions can cause the electrical problems that lead to SCA. Examples include coronary heart disease(CHD), also called coronary artery disease; severe physical stress; certain inherited disorders; and structural changes in the heart.

Several research studies are under way to try to find the exact causes of SCA and how to prevent them.

Coronary Heart Disease

CHD is a disease in which a waxy substance called plaque (plak) builds up in the coronary arteries. These arteries supply oxygen-rich blood to your heart muscle.

Plaque narrows the arteries and reduces blood flow to your heart muscle. Eventually, an area of plaque can rupture (break open). This may cause a blood clot to form on the plaque’s surface.

A blood clot can partly or fully block the flow of oxygen-rich blood to the portion of heart muscle fed by the artery. This causes a heart attack.

During a heart attack, some heart muscle cells die and are replaced with scar tissue. The scar tissue damages the heart’s electrical system. As a result, electrical signals may spread abnormally throughout the heart. These changes to the heart increase the risk of dangerous arrhythmias and SCA.

CHD seems to cause most cases of SCA in adults. Many of these adults, however, have no signs or symptoms of CHD before having SCA.

Physical Stress

Certain types of physical stress can cause your heart’s electrical system to fail. Examples include:

• Intense physical activity. The hormone adrenaline is released during intense physical activity. This hormone can trigger SCA in people who have heart problems.
• Very low blood levels of potassium or magnesium. These minerals play an important role in your heart’s electrical signaling.
• Major blood loss.
• Severe lack of oxygen.

Inherited Disorders

A tendency to have arrhythmias runs in some families. This tendency is inherited, which means it’s passed from parents to children through the genes. Members of these families may be at higher risk for SCA.

An example of an inherited disorder that makes you more likely to have arrhythmias is long QT syndrome (LQTS). LQTS is a disorder of the heart’s electrical activity. Problems with tiny pores on the surface of heart muscle cells cause the disorder. LQTS can cause sudden, uncontrollable, dangerous heart rhythms.

People who inherit structural heart problems also may be at higher risk for SCA. These types of problems often are the cause of SCA in children.

Structural Changes in the Heart

Changes in the heart’s normal size or structure may affect its electrical system. Examples of such changes include an enlarged heart due to high blood pressure or advanced heart disease. Heart infections also may cause structural changes in the heart.

Who Is At Risk for Sudden Cardiac Arrest?

Sudden cardiac arrest occurs most often in people in their mid-thirties to mid-forties. It appears to affect men twice as often as women.

Sudden cardiac arrest rarely occurs in children unless they have inherited problems that make them likely to have sudden cardiac arrest. Only a very small number of children have sudden cardiac arrest each year.

Major Risk Factors

The major risk factor for sudden cardiac arrest is undiagnosed coronary artery disease (CAD). Most people who have sudden cardiac arrest are later found to have some degree of CAD. Most of these people don’t know that they have CAD until sudden cardiac arrest occurs.

Their CAD is “silent”—that is, it has no signs or symptoms. Because of this, doctors and nurses have not detected it. Most cases of sudden cardiac arrest happen in people who have silent CAD and who have no known heart disease prior to sudden cardiac arrest.

Many people who have sudden cardiac arrest also have a silent, or undiagnosed, heart attack before sudden cardiac arrest happens. These people have no obvious signs of heart attack, and they don’t even realize that they’ve had one. The chances for having sudden cardiac arrest are higher during the first 6 months after a heart attack.

Other Risk Factors

Other risk factors for sudden cardiac arrest include:

• A personal or family history of sudden cardiac arrest or of inherited disorders that make you prone to arrhythmias
• A history of having arrhythmias
• Heart attack
• Heart failure
• Drug abuse or excessive alcohol intake

complications:

When sudden cardiac arrest occurs, your brain is the first part of your body to suffer because, unlike other organs, it doesn’t have a reserve of oxygen-rich blood. It’s completely dependent on an uninterrupted supply of blood. Reduced blood flow to your brain causes unconsciousness.

If your heart rhythm doesn’t rapidly return to its normal rhythm, brain damage occurs and death results. If sudden cardiac arrest lasts more than 10 minutes, survival is rare. Survivors of cardiac arrest may show signs of brain damage.

How Is Sudden Cardiac Arrest Diagnosed?

Sudden cardiac arrest (SCA) happens without warning and requires emergency treatment. Doctors rarely diagnose SCA with medical tests as it’s happening. Instead, SCA often is diagnosed after it happens. Doctors do this by ruling out other causes of a person’s sudden collapse.

Specialists Involved

If you’re at high risk for SCA, your doctor may refer you to a cardiologist. This is a doctor who specializes in diagnosing and treating heart diseases and conditions. Your cardiologist will work with you to decide whether you need treatment to prevent SCA.

Some cardiologists specialize in problems with the heart’s electrical system. These specialists are called cardiac electrophysiologists.

Diagnostic Tests and Procedures

Doctors use several tests to help detect the factors that put people at risk for SCA.

EKG (Electrocardiogram)

An EKG is a simple, painless test that detects and records the heart’s electrical activity. The test shows how fast the heart is beating and its rhythm (steady or irregular). An EKG also records the strength and timing of electrical signals as they pass through each part of the heart.

An EKG can show evidence of heart damage due to coronary heart disease (CHD). The test also can show signs of a previous or current heart attack.

Echocardiography

Echocardiography, or echo, is a painless test that uses sound waves to create pictures of your heart. The test shows the size and shape of your heart and how well your heart chambers and valves are working.

Echo also can identify areas of poor blood flow to the heart, areas of heart muscle that aren’t contracting normally, and previous injury to the heart muscle caused by poor blood flow.

There are several types of echo, including stress echo. This test is done both before and after a cardiac stress test. During this test, you exercise (or are given medicine if you’re unable to exercise) to make your heart work hard and beat fast.

Stress echo shows whether you have decreased blood flow to your heart (a sign of CHD).

MUGA Test or Cardiac MRI

A MUGA (multiple gated acquisition) test shows how well your heart is pumping blood. For this test, a small amount of radioactive substance is injected into a vein and travels to your heart.

The substance releases energy, which special cameras outside of your body can detect. The cameras use the energy to create pictures of many parts of your heart.

Cardiac MRI (magnetic resonance imaging) is a safe procedure that uses radio waves and magnets to create detailed pictures of your heart. The test creates still and moving pictures of your heart and major blood vessels.

Doctors use cardiac MRI to get pictures of the beating heart and to look at the structure and function of the heart.

Cardiac Catheterization

Cardiac catheterization is a procedure used to diagnose and treat certain heart conditions. A long, thin, flexible tube called a catheter is put into a blood vessel in your arm, groin (upper thigh), or neck and threaded to your heart. Through the catheter, your doctor can do diagnostic tests and treatments on your heart.

Sometimes dye is put into the catheter. The dye will flow through your bloodstream to your heart. The dye makes your coronary (heart) arteries visible on x-ray pictures. The dye can show whether plaque has narrowed or blocked any of your coronary arteries.

Electrophysiology Study

For an electrophysiology study, doctors use cardiac catheterization to record how your heart’s electrical system responds to certain medicines and electrical stimulation. This helps your doctor find where the heart’s electrical system is damaged.

Blood Tests

Your doctor may recommend blood tests to check the levels of potassium, magnesium, and other chemicals in your blood. These chemicals play an important role in your heart’s electrical signaling.

treatment:

Emergency Treatment

Sudden cardiac arrest (SCA) requires immediate treatment with a defibrillator. This device sends an electric shock to the heart. The electric shock may restore a normal rhythm to a heart that’s stopped beating.

To work well, defibrillation must be done within minutes of sudden cardiac arrest. With every minute that passes, the chances of surviving sudden cardiac arrest drop rapidly.

Police, emergency medical technicians, and other first responders usually are trained and equipped to use a defibrillator. Call 9–1–1 right away if someone has signs or symptoms of sudden cardiac arrest. The sooner help is called, the sooner potentially lifesaving treatment can be done.

Automated External Defibrillators

Automated external defibrillators (AEDs) are special defibrillators that untrained bystanders can use. These devices are becoming more available in public places like airports, office buildings, and shopping centers.

AEDs are programmed to give an electric shock if they detect a dangerous arrhythmia, such as ventricular fibrillation. This prevents giving a shock to someone who may have fainted but isn’t having sudden cardiac arrest.

Cardiopulmonary resuscitation (CPR) should be given to a person having sudden cardiac arrest until defibrillation can be done.

People who are at risk for sudden cardiac arrest may want to consider having an AED at home. Currently, one AED, the Phillips HeartStart Home Defibrillator, is sold over-the-counter for home use.

The benefits of home-use AEDs are still debated. Some people feel that placing these devices in homes will save many lives, because many sudden cardiac arrests occur at home.

Others note that no evidence supports the idea that home-use AEDs save more lives. These people fear that people who have AEDs in their homes will delay calling for help during an emergency. They’re also concerned that people who have home-use AEDs will not properly maintain the devices or forget where they are.

A large study on AEDs is currently under way. It may provide information on the pros and cons of having an AED in the home.

When considering a home-use AED, talk to your doctor. He or she can help you decide whether having an AED in your home will benefit you.

Treatment in a Hospital

If you survive sudden cardiac arrest, you usually will be admitted to a hospital for observation and treatment. In the hospital, your medical team will closely watch your heart. They may give you medicines to try to reduce the chance of another sudden cardiac arrest.

While in the hospital, your medical team will try to find out what caused your sudden cardiac arrest. If you’re diagnosed with coronary artery disease, you may have angioplasty or coronary artery bypass grafting. These procedures help restore blood flow through narrowed or blocked coronary arteries.

Often, people who have sudden cardiac arrest get a device called an implantable cardioverter defibrillator (ICD). This small device is surgically placed under the skin in your chest or abdomen. An ICD uses electric pulses or shocks to help control dangerous arrhythmias.

prevention:

Ways to prevent death due to sudden cardiac arrest (SCA) differ depending on whether:

• You’ve already had sudden cardiac arrest
• You’ve never had sudden cardiac arrest but are at high risk for the condition
• You’ve never had sudden cardiac arrest and have no known risk factors for the condition

For People Who Have Survived Sudden Cardiac Arrest

If you’ve already had sudden cardiac arrest, you’re at high risk of having it again. Research shows that an implantable cardioverter defibrillator (ICD) reduces the chances of dying from a second sudden cardiac arrest.

An ICD is surgically placed under the skin in your chest or abdomen. The device has wires with electrodes on the ends that connect to your heart’s chambers. The ICD monitors your heartbeat.

If the ICD detects a dangerous heart rhythm, it gives an electric shock to restore the heart’s normal rhythm. Your doctor may give you medicine to limit irregular heartbeats that can trigger the ICD.

Implantable Cardioverter Defibrillator

The illustration shows the location of an implantable cardioverter defibrillator in the upper chest. The electrodes are inserted into the heart through a vein.

An ICD isn’t the same as a pacemaker. The devices are similar, but have some differences. Pacemakers only give off low-energy electrical pulses. They’re often used to treat less dangerous heart rhythms, such as those that occur in the upper chambers of the heart. Most new ICDs work as both pacemakers and ICDs.

For People at High Risk for a First Sudden Cardiac Arrest

If you have severe coronary artery disease (CAD), you’re at increased risk for sudden cardiac arrest. This is especially true if you’ve recently had a heart attack.

Your doctor may prescribe a type of medicine called a beta blocker to help lower your risk for sudden cardiac arrest. Other treatments for CAD, such as angioplasty or coronary artery bypass grafting, also may lower your risk for sudden cardiac arrest.

Your doctor also may recommend an ICD if your risk for sudden cardiac arrest is very high.

For People Who Have No Known Risk Factors for Sudden Cardiac Arrest

CAD seems to be the cause of most cases of sudden cardiac arrest in adults. CAD also is a major risk factor for angina (chest pain or discomfort) and heart attack, and it contributes to other heart problems.

Following a healthy lifestyle can help you lower your risk for CAD, sudden cardiac arrest, and other heart problems.

Healthy Diet and Physical Activity

A healthy diet is an important part of a heart healthy lifestyle. Choose a variety of fruits, vegetables, and grains; half of your grains should come from whole-grain products.

Choose foods that are low in saturated fat, trans fat, and cholesterol. Healthy choices include lean meats, poultry without skin, fish, beans, and fat-free or low-fat milk and milk products.

Choose and prepare foods with little sodium (salt). Too much salt can raise your risk for high blood pressure. Recent studies show that following the Dietary Approaches to Stop Hypertension (DASH) eating plan can lowerblood pressure.

Choose foods and beverages that are low in added sugar. If you drink alcoholic beverages, do so in moderation.

Aim for a healthy weight by staying within your daily calorie needs. Balance the calories you take in with the calories you use while doing physical activity. Be as physically active as you can.

Some people should get medical advice before starting or increasing physical activity. For example, talk to your doctor if you have a chronic (ongoing) health problem, are on medicine, or have symptoms such as chest pain, shortness of breath, or dizziness. Your doctor can suggest types and amounts of physical activity that are safe for you.

Other Lifestyle Changes

Other lifestyle changes also can help lower your risk for sudden cardiac arrest. Examples include:

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