What to know about cardiac arrest and how common it is among young athletes like Bronny James

At 18, Bronny James is the picture of a young, healthy athlete at the top of his game.

But the incoming USC freshman and son of NBA great LeBron James suffered a frightening medical emergency Monday during practice on campus at the Galen Center. He collapsed during the workout due to cardiac arrest -- a serious and potentially lethal health threat that can happen without warning, even in young, healthy and athletic individuals.

In the critical moments after James' collapse, trained medical staff at the practice provided immediate medical care, similar to the pivotal moments that followed the on-field cardiac arrest of Buffalo Bill Damar Hamlin last year during an NFL game.

In a statement, the James family Tuesday said his condition was stable.

"Yesterday while practicing Bronny James suffered a cardiac arrest," the family said in the statement. "Medical staff was able to treat Bronny and take him to the hospital. He is now in stable condition and no longer in ICU. We ask for respect and privacy for the James family and we will update media when there is more information.

"LeBron and Savannah wish to publicly send their deepest thanks and appreciation to the USC medical and athletic staff for their incredible work and dedication to the safety of their athletes."

James, a McDonald's All-American after his senior season, is a 6-foot-3, 180-pound guard. He was the No. 20 ranked player in his recruiting class, according to ESPN. He had offers from Kentucky, Ohio State, Michigan, Memphis and Oregon before committing to USC in May.

Here's what to know about cardiac arrest and what it means for young and healthy individuals, like James and Hamlin.

What is cardiac arrest?

The heart suddenly and unexpectedly stops pumping blood to the brain, kidney, liver and other important organs. Someone in cardiac arrest commonly will stop breathing, leading to a loss of consciousness and collapse. Without oxygen rich blood, vital organs can't survive.

Is cardiac arrest the same as a heart attack?

A heart attack is different. Blood flow to the heart is blocked or limited during a heart attack, resulting in tell-tale chest pain.

How is cardiac arrest treated?

The race against time begins right away, often with potentially life-saving CPR. Permanent brain damage can result in as little as five minutes without enough oxygen-rich blood. Death may follow.

But CPR, which bridges the care gap until a patient is hospitalized, can double the chance of survival from a cardiac arrest happening outside a hospital setting, according to the Centers for Disease Control and Prevention.

"Kudos to that team for recognizing his distress and responding immediately," said NBC Los Angeles medical expert Nurse Alice Benjamin. "When this happens, someone's heart has stopped beating, someone has stopped breathing, it's a medical emergency. We're getting you to the ICU."

Patients are often intubated in the emergency room to assist with breathing. Doctors will monitor the heart and examine bloodwork, looking for anything indicating a cause.

"We're giving different types of medications to optimize the output of the heart while minimizing its workload," Nurse Alice said. "We want the heart to pump, but we want to decrease any workload from it."

How common is cardiac arrest among young people?

Cardiac arrest is rare among people under age 35. Dr. Rory Weiner, a sports cardiologist at Massachusetts General Hospital in Boston, told NBC News that 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.

Of note, college basketball players have one of the higher rates of fatal cardiac arrest among young athletes.

More than 356,000 out-of-hospital cardiac arrests happen every year in the United States, according to the American Heart Association. About 90% of them are fatal. Older adults and men are at the highest risk for cardiac arrest, according to the Centers for Disease Control and Prevention.

What causes cardiac arrest?

In athletes older than 35, cardiac arrest is usually attributed to coronary disease. Plaque builds up in the arteries of the heart over time, leading to cardiac arrest.

Causes for people under 35 are not always clear. It may be attributed to genetic defects, heart malfunctions or a structural problem with the heart and its complex components.

"It's usually from a congenital heart disease," said Nurse Alice. "We don't know that for sure in this case. But, according to the CDC, about 2,000 otherwise healthy young people under the age of 25 die from cardiac arrest every year."

As for symptoms, the cardiac arrest itself is unfortunately often the first sign among young athletes. People with underlying conditions might report heart palpitations and shortness of breath prior to cardiac arrest.

What happens during cardiac arrest recovery?

Cardiac arrest is a severe injury to the heart -- an injury that requires time for recovery.

What that recovery will look like depends largely on the cause of the injury. Doctors will run tests to determine whether a structural or functional issue led to cardiac arrest. During that time, the patient will need to take it easy.

"Strenuous activity is no where in the next couple of weeks for him," Nurse Alice said. "He definitely needs to give his heart a rest. This is something that's very significant and major."

A cardiac arrest patient will likely remain in the hospital for a few days while doctors determine the cause.

"If it was a structural issue, it might require surgery," Nurse Alice said. "If it was something about his electrolytes, maybe they can replace them."

The 25-year-old Hamlin was cleared to return to football in mid-April. He practiced for the first time since the terrifying on-field emergency in early June.

Last summer, USC center Vince Iwuchukwu collapsed due to cardiac arrest during a basketball practice and was revived by the team's training staff. He made a full recovery and returned to the team.