The sudden collapse of Buffalo Bills player Damar Hamlin during Monday night's game against the Cincinnati Bengals left millions of Americans in shock and anxiously waiting for news of his condition.
"Damar Hamlin suffered a cardiac arrest following a hit in our game versus the Bengals," the Bills tweeted early Tuesday. "His heartbeat was restored on the field and he was transferred to the UC Medical Center for further testing and treatment. He is currently sedated and listed in critical condition."
The 24-year-old remains in the intensive care unit, according to the Bills. Family spokesperson Jordon Rooney told "Good Morning America" that the family is "in good spirits" and "taking it minute by minute."
Despite confirmation about the medical episode Hamlin suffered, the term "cardiac arrest" is often used interchangeably with the term "heart attack," even though the two are not the same.
"This differentiation between cardiac arrest and heart attack is really important because they are two things that can both occur in the same person or be completely separate," Dr. Deepak Bhatt, an expert in cardiovascular medicine and director of Mount Sinai Heart in New York City, told ABC News.
Heart attack vs. cardiac arrest
Heart attacks occur when a coronary artery leading to the heart is blocked, which prevents blood from reaching the organ.
Meanwhile, "a cardiac arrest essentially is the cessation of heart activity or a stopping of the heart pumping, which is generally due to what's called an arrhythmia or an electrical disturbance of the heart," Dr. Matthew Saybolt, a cardiologist with Jersey Shore University Medical Center, told ABC News.
One good way to differentiate between the two is to think of a heart attack as a "circulation" problem and cardiac arrest as an "electrical" problem, according to the American Heart Association.
While cardiac arrest can occur immediately following a heart attack or during recovery -- and heart attacks increase the risk of cardiac arrest -- one does not have to be preceded by the other.
"Heart attacks can cause a cardiac arrest but not all cardiac arrests are due to a heart attack and not all heart attacks result in a cardiac arrest," Bhatt said.
Heart attacks are primarily caused by coronary heart disease, which is when heart arteries can't deliver enough oxygen-rich blood to the heart.
This happens because of atherosclerosis, which is the narrowing of blood vessels from plaque build-up made of fat, cholesterol, and other substances. Risk factors for atherosclerosis and having a heart attack include older age, male sex, smoking, diabetes, high blood pressure, and high cholesterol, among others.
Cardiac arrest meanwhile can be caused by several conditions, including ventricular fibrillation, a type of arrhythmia where the lower chambers of the heart don't beat normally; coronary artery disease; heart failure; congenital heart disease; and commotio cordis, experts said.
The latter condition occurs when the heart's rhythm is disrupted due to a blow to the chest that lands at a very specific moment in the heartbeat. It's most typically seen with athletes who play sports with projectiles, including baseballs and hockey pucks.
"Classically, where I've seen it before is a baseball player line drive to the chest of the pitcher and then the pitcher collapses," Bhatt said. "And even though that's a young, healthy pitcher, that sudden line drive to the chest has hit their heart at just the wrong time in the heart's electrical cycle such that it triggers an abnormal heart rhythm."
Symptoms between a heart attack and cardiac arrest also vary. The most common symptoms of a heart attack are chest pain or discomfort; pain or discomfort in one or both arms, the back, neck, jaw or stomach; shortness of breath; and lightheadedness or dizziness, according to the AHA.
Patients can have immediate symptoms, symptoms that start mildly and then progress and, in some cases, no symptoms at all.
Comparatively, the symptoms of a cardiac arrest patient are immediate and often without warning. They include loss of consciousness or collapse with faint or loss of pulse, often with labored breathing or no breathing at all.
How to help save patients
In both instances, experts say to check for responsiveness then shout for nearby help and to call 911 or your local emergency number so the patient can immediately receive medical attention.
When it comes to someone experiencing cardiac arrest, call for or find an automated external defibrillator, or an AED, and use it as soon as possible.
AEDs, which are located in most public buildings -- including restaurants, sporting events and workplaces -- are medical devices that analyze the heart's rhythm and will deliver an electrical shock if needed. Experts add that you don't need to worry about hurting the patient when using it.
"If the AED thinks that the patient is in an arrhythmia that needs to be shocked that AED will figure that out and deliver that shock," Dr. Michael Emery, a cardiologist and co-director of the Sports Cardiology Center at Cleveland Clinic, told ABC News. "You as a bystander do not have to figure out whether you need to shock this patient at all. Whether they're having a heart attack or not or they're having a cardiac arrest, the AED is smart enough to figure that out all on its own. All you have to do is call 911, get the AED and apply it."
The other important thing to do is begin cardiopulmonary resuscitation, or CPR as soon as possible. If it's performed on a patient immediately, it can double or triple the odds of survival, according to the AHA.
Hamlin quickly received CPR after he collapsed on the field, which helped resuscitate him long enough to be transported to a hospital.
"Bystander CPR is life-saving," Emery said. "What we know is that for every minute that you delay resuscitation in the setting of an arrest, the outcomes drastically worsen. So, the sooner you can start CPR and apply an AED, the more likely that patient is going to survive just from a pure timing standpoint."
"There are instances where people's heart can stop for a long period of time, but with good CPR, that bystander CPR can keep the patient alive for a long time until next-level medical attention can either shock the heart or treat the condition that caused all this," Saybolt added.
The experts said they hope the situation helps people learn to recognize the symptoms of heart attacks and cardiac arrest and encourages them to learn CPR.
"Even if you're thinking, 'Oh, I'm never going to need to do that,' by getting that sort of training, you're more likely to help someone, you know, a friend or a coworker or a family member," Bhatt said. "So, I think it's really a good idea for everyone to do that, to get that sort of basic training just so that you can potentially save someone's life."
ABC News' Nicole Wetsman contributed to this report.