Cardiac arrest is usually sudden and shocking. It can occur without warning, even in young, healthy people.

LeBron James’ 18-year-old son, Bronny, is recovering after he collapsed during training in Los Angeles on Monday and was rushed to hospital.

“Yesterday while practicing, Bronny James went into cardiac arrest. Medical staff were able to treat Bronny and take him to the hospital,» according to a statement from the family. He is now in stable condition and is no longer in the ICU, according to the family.

Here’s what you need to know about cardiac arrest.

What is a cardiac arrest?

Cardiac arrest occurs when the heart stops beating and stops pumping blood to the rest of the body. At such times, the brain and other vital organs do not receive the oxygen-rich blood they need to survive.

Cardiac arrest is different from a heart attack, which occurs when blood flow to the heart muscle is limited or blocked, causing the classic symptom of chest pain.

Sierra Canyon guard Bronny James takes a shot during warm ups on January 7 in Los Angeles.Brian Rothmuller/Icon Sportswire via AP

Prompt recognition and rapid initiation of CPR are vital: permanent brain damage can occur in as little as five minutes if oxygen-rich blood does not reach the brain, and death may occur soon after. Fortunately, if done right away, CPR can double your chances of survival from cardiac arrest that occurs outside of a hospital setting. according to the Centers for Disease Control and Prevention.

What causes cardiac arrest?

The patient’s age can play a role in causing sudden cardiac arrest, said Dr. Eugene Chung, a sports cardiologist at the University of Michigan.

In athletes older than 35, it’s often attributed to coronary heart disease, Chung said, referring to age-related plaque buildup in the heart’s arteries.

But for those under 35, the causes of sudden cardiac arrest aren’t clear. It could be the result of genetic defects, as well as heart malfunctions such as a heart attack or heart valve problems.

Dr. Nahush Mokadam, director of the division of cardiac surgery at The Ohio State University Wexner Medical Center, said it can be difficult for people to understand why an apparently healthy young athlete collapses from cardiac arrest.

«Everyone wants to point the finger in these scenarios,» Mokadam said. «I think it’s important to realize that there are a lot of things that can lead to sudden cardiac arrest in young people that are out of everyone’s control, despite everyone’s best interests, best due diligence and the rest.»

How common is cardiac arrest?

The rate of cardiac arrest in the general population each year is about 1 in 1,000, according to Mayo Clinic Estimates.

While the exact incidence of cardiac arrest among athletes is not known, Dr. Rory Weiner, a sports cardiologist at Massachusetts General Hospital in Boston, said the number of young athletes who die of cardiac arrest is estimated to be between 1 in 50,000 and 1 in 100,000 per year.

He pointed out, however, that it can vary according to the sport practiced and the gender of the athlete. For reasons yet to be determined, college basketball players, he said, they have one of the highest rates of fatal cardiac arrest.

According to the American Heart Association, every year more than 356,000 Out-of-hospital cardiac arrests occur in the US, and about 90% of them are fatal. Almost all cases occurred in private homes, while a minority occurred in public places or nursing homes.

Older adults and men are at the highest risk of cardiac arrest, according to the Centers for Disease Control and Prevention, with about 2,000 apparently healthy people under the age of 25 die of her every year.

What are the symptoms of cardiac arrest?

Nearly half of patients who experience cardiac arrest report that they had no symptoms before collapsing. However, some patients may experience palpitations or dizziness prior to cardiac arrest.

“One of the difficult things about sudden cardiac arrest in athletes is that cardiac arrest can be the first symptom,” Weiner said. People with underlying conditions may experience some symptoms before arrest, such as heart palpitations or shortness of breath, he said.

Signs to look for if you suspect someone might be in cardiac arrest include someone losing consciousness and not responding to shoulder taps and breathing that seems unusual, according to the American Heart Association. If this occurs, the first step is to call 911 and high-quality CPR in the form of chest compressions should be started immediately.

Can cardiac arrest be prevented by screening athletes?

It has been a matter of debate whether or not to test healthy people for heart disease, Chung said.

People who already show symptoms of heart problems, such as chest pain and shortness of breath, should be screened, Chung said.

Weiner agreed, adding that testing everyone who wants to play team sports isn’t the best approach and could lead to false positives, creating even more anxiety for parents and kids.

Beyond taking a detailed medical history and performing a physical exam, additional screening tests, such as EKGs and imaging tests for athletes in the US, aren’t «really feasible,» Weiner said.

For parents and coaches concerned about sudden cardiac arrest, all the cardiologists said the top recommendation is to learn to recognize it and apply immediate treatment, including CPR.

«In this case, there were medical personnel around him, the coaches and staff were all there,» Mokadam said. «But this could happen, you know, on a playground, and if it happens on a playground, if everyone knows CPR, we can save lives.»