The heart pumps blood. 

The heart pumps blood through the body. 
When the heart stops, blood cannot move. It cannot reach the brain or other parts. This can make a person pass out.
This often happens because the heart beats in a strange way. It may not have a steady rhythm.
Doctors use special tools to help. They can use chest presses called CPR. 
Helping the heart quickly is very important. This helps the person get better.
Cardiac arrest is when the heart suddenly stops beating. 
When the heart stops, blood cannot move through the body. This means the brain and other organs do not get blood. Without blood, brain cells can die in just a few minutes. A person might lose consciousness or pass out.
This often happens because of an arrhythmia. An arrhythmia is an irregular heart rhythm. The heart may beat too fast or in a strange way. This stops the heart from pumping blood well.
Many things can cause this. Some people have heart disease. This is when blood flow is blocked in the heart's tubes. 
Other causes include high blood pressure. This can make the heart's main pump grow too large. This is called hypertrophy. 
Doctors work fast to help. They use CPR to press on the chest. They may also use a machine to shock the heart. This is called defibrillation. 
In the United States, about 535,000 people have cardiac arrest each year. Most of these happen outside of a hospital.
Cardiac arrest is a serious medical event. It happens when the heart suddenly stops beating. 

Most cardiac arrests happen because of an arrhythmia. An arrhythmia is an irregular heart rhythm. The heart uses electrical signals to pump. If the rhythm is wrong, the heart cannot pump blood properly. This is called hemodynamic collapse. Two common types are ventricular tachycardia and ventricular fibrillation. In these states, the heart muscle does not contract in a coordinated way. 
Many different things can cause the heart to stop. One common cause is coronary artery disease. This happens when cholesterol builds up in the heart's arteries. 

In the United States, about 535,000 cardiac arrests happen every year. This is about 13 incidents for every 10,000 people. Most of these, about 61 percent, happen outside of a hospital. Only 39 percent happen inside a hospital setting. Cardiac arrest is more common as people get older. It also affects males more often than females. In the U.S., black people are twice as likely to die from it as white people.
Doctors and bystanders work quickly to help a person. The goal is to achieve return of spontaneous circulation. This means getting the heart beating on its own again. People use CPR to help pump blood manually. 

Cardiac arrest, often called sudden cardiac arrest (SCA), is a critical medical condition. It occurs when the heart suddenly and unexpectedly stops beating. 

The most common cause of cardiac arrest is an arrhythmia. An arrhythmia is an irregular heart rhythm caused by disrupted electrical activity. 
Many different cardiac issues can lead to these irregular rhythms. One leading cause is coronary artery disease (CAD). 
Structural heart disease is another significant cause of cardiac arrest. This refers to physical changes in the heart's shape or strength. For example, long-standing high blood pressure can cause left ventricular hypertrophy. 
Some people experience cardiac arrest due to inherited arrhythmia syndromes. These are often caused by genetic mutations in ion channels. These channels are specialized proteins that move electrically charged particles across cell membranes. These conditions are sometimes called channelopathies. Examples include long QT syndrome (LQTS), Brugada syndrome, and short QT syndrome. These syndromes can be triggered by environmental factors, such as loud sounds. These genetic causes account for 5 to 10 percent of all sudden cardiac arrests. They often affect younger populations more significantly than structural diseases do.
In the United States, there are approximately 535,000 cardiac arrest incidents every year. This represents about 13 incidents for every 10,000 people. About 61 percent of these events, or 326,000 cases, happen outside of a hospital. The remaining 39 percent, or 209,000 cases, occur within a hospital setting. Cardiac arrest is more common in males and becomes more frequent as people age. Statistics show that black people in the U.S. are twice as likely to die from cardiac arrest as white people. Asian and Hispanic populations are affected less frequently than white populations.
Medical teams work to achieve return of spontaneous circulation (ROSC). This means getting the heart to beat on its own again. 

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