Cardiac arrest can strike without warning, and the person who recognizes it in the first minute or two often decides the outcome. This guide gives you a recognition-first sequence for how to recognize cardiac arrest symptoms: check responsiveness, check breathing, call, compress, and use an AED. You will also learn how cardiac arrest differs from a heart attack and which mistakes waste the most time. You need no training to start and no equipment beyond your hands, though a hands-on CPR and AED course makes each step faster and more confident.

Step 1: Understand What Cardiac Arrest Is and How It Differs From a Heart Attack

Cardiac arrest is an electrical problem. The heart's rhythm malfunctions, often into a chaotic quivering called ventricular fibrillation, and the heart stops pumping blood effectively. Blood flow to the brain and other organs stops almost immediately. The person collapses, does not respond, and does not breathe normally.

A heart attack is a circulation problem. A blockage cuts off blood flow to part of the heart muscle, which begins to be damaged. The heart usually keeps beating, so the person is typically awake and breathing. They may have chest pressure or pain, discomfort spreading to the arm, jaw, or back, shortness of breath, nausea, or a cold sweat.

The two are connected. A heart attack can scar or irritate the heart and trigger a dangerous rhythm, so a heart attack can lead to cardiac arrest. But many cardiac arrests happen with no heart attack at all.

The terms are not interchangeable, and confusing them is costly. If you treat a collapsed, unresponsive person as someone having a heart attack, you may sit them down, ask how they feel, or wait to see if they improve. Someone in cardiac arrest cannot answer, and every minute without CPR and defibrillation reduces the chance of survival. The rule to carry forward: if a person is awake and talking, call emergency services and keep them calm and resting. If they are unresponsive and not breathing normally, treat it as cardiac arrest and begin the steps below.

Step 2: Check for Unresponsiveness

Before you approach, take two seconds to scan the scene. Look for traffic, exposed electrical sources, spilled liquid near equipment, fire, or unstable structures. If the area is unsafe, call for help and wait for responders rather than becoming a second victim. If you can safely move the person out of immediate danger, do so, but do not delay care for a tidy setting.

Once the scene is safe, kneel beside the person and tap their shoulders firmly. Shout their name if you know it, or ask loudly, "Are you okay?" Use enough force that a sleeping person would wake. You are looking for three things:

No verbal response
No purposeful movement, such as turning toward you or pushing your hand away
No eye opening in reaction to your voice or touch

A person who groans or twitches without responding to you meaningfully should still be treated as unresponsive.

Mistake to avoid: assuming the person is fainting or sleeping. This happens most often when someone is slumped in a chair, lying in bed, or has just fallen. A person who faints usually recovers within a minute or so. If they do not respond to your voice and touch, do not wait to see whether they come around. Treat it as an emergency and move straight to checking breathing.

Step 3: Look for Absent or Abnormal Breathing

With the person on their back on a firm surface, watch the chest and belly for no more than 10 seconds. Normal breathing is regular, with visible rise and fall. If you see no movement, or only occasional gasps, cardiac arrest is likely.

Recognize agonal breathing

Agonal breathing is slow, irregular, often noisy gasping, sometimes described as snorting, gurgling, or like a fish out of water. It can occur in the first minutes of cardiac arrest because the brainstem is still firing reflexively. It is not effective breathing and does not deliver useful oxygen. It can also be mistaken for a sign of life, which makes it one of the most dangerous misreadings in an emergency. Dispatchers are trained to ask about it for this reason.

The common mistake is waiting for the gasping to stop, or taking it as a sign the person is recovering. Do neither. If someone is unresponsive and only gasping, act as though they are not breathing.

Skip the pulse check if you are a lay rescuer

Pulses are hard to find, even for experienced people, and hunting for one wastes time. If you are not a healthcare provider, rely on responsiveness and breathing alone. Healthcare providers performing BLS may check a carotid pulse at the same time as they check breathing, taking no more than 10 seconds. If no pulse is clearly felt, or you are unsure, begin compressions.

You do not need to be certified to act. If the person is unresponsive and not breathing normally, you have enough information to begin the response.

Step 4: Notice Warning Signs That Can Come Before Collapse

Most cardiac arrests are recognized at the moment of collapse, not by earlier symptoms, and many people have no warning at all. Still, some do. Symptoms that can appear hours, days, or weeks before include:

Chest discomfort or pressure
Shortness of breath out of proportion to activity
Palpitations, meaning a racing, pounding, or fluttering heartbeat
Lightheadedness or dizziness
Fainting or near-fainting

The American Heart Association has noted that some people experience symptoms such as chest pain or palpitations before sudden cardiac arrest, but you should not rely on warning signs being present. Their absence does not mean someone is safe, and their presence does not mean arrest is certain.

Treat certain faints as urgent

Fainting during exercise, or fainting accompanied by a racing or irregular heartbeat, deserves prompt medical evaluation. Do not write it off as dehydration or a bad day. If the person has not recovered, is confused, or has chest pain, call emergency services. If they have recovered, they still need to see a clinician soon, because an unexplained faint can be the only signal of a dangerous rhythm disorder.

Know the higher-risk situations

Stay alert around people who have:

Known heart disease, a previous heart attack, or heart failure
A family history of sudden cardiac death, especially at a young age
Intense athletic demands, particularly if they have had unexplained fainting or palpitations
Older age, since risk rises with age

If you coordinate safety at a workplace, gym, or school, this is where to focus your attention and your AED planning. Awareness of risk makes you faster to act, but the response in Steps 2 and 3 applies to anyone who collapses.

Step 5: Call Emergency Services and Send for an AED

As soon as you find someone unresponsive and not breathing normally, call 911, or the local emergency number if you are outside the United States. Put the phone on speaker so both hands are free. Tell the dispatcher your location, that the person is unresponsive and not breathing normally, and answer their questions without hanging up.

If other people are nearby, do not shout a general request such as "Someone call 911." Bystanders often assume somebody else has done it. Point at a specific person and give a specific task:

"You in the blue jacket, call 911 and stay on the line."
"You, get the AED and bring it here."
"You, meet the ambulance at the entrance and guide them in."

If you are alone, call first, using speaker, and start compressions right away. If an AED is visibly within a few steps, grab it, but do not leave the person for a long search.

Dispatchers are trained to coach bystanders through CPR. They can tell you where to place your hands and keep your pace, and for untrained bystanders they typically guide compression-only CPR, meaning chest compressions without rescue breaths. Follow their instructions even if you feel unsure.

Tip: know where AEDs are before you need one. An AED is a portable device that analyzes the heart rhythm and delivers a shock if needed. In your workplace, gym, or building, find them on a normal day. AED cabinets are commonly found near entrances, lobbies, and elevators, but locations vary. Knowing yours saves precious time when seconds matter.

Step 6: Begin Chest Compressions and Use the AED

Do not wait for the ambulance. Start compressions immediately.

Kneel beside the person, who should be flat on their back on a firm surface.
Place the heel of one hand on the center of the chest, on the lower half of the breastbone, and put your other hand on top. Lock your elbows and position your shoulders over your hands.
Push hard and fast. As of 2026, American Heart Association guidance calls for a rate of 100 to 120 compressions per minute and a depth of about 2 inches (5 cm) for adults. Confirm against the latest AHA guidelines if you are teaching or writing procedures.
Let the chest fully recoil between compressions, and minimize any pauses.

Fatigue sets in quickly. If another person is available, swap roles about every two minutes, ideally during AED analysis, so the pace and depth stay effective.

Use the AED as soon as it arrives

Turn it on and follow the voice prompts. Bare the chest, dry it if wet, and attach the pads in the positions shown on the pad illustrations. Make sure no one is touching the person, and let the device analyze the rhythm. If it advises a shock, make sure everyone is clear and press the button. Whether it delivers a shock or says no shock is needed, resume compressions immediately. AEDs are designed for untrained users and will not shock a rhythm that does not need it.

Do not stop until EMS takes over, the person clearly wakes up and begins breathing normally, or the AED prompts you to pause for analysis.

Do not let fear hold you back

Many people hesitate because they worry about hurting the person. Compressions can break ribs, particularly in older adults. That injury is treatable, and it is far less harmful than doing nothing, since a person in cardiac arrest will not survive without circulation. Many regions have Good Samaritan laws that protect people who give emergency help in good faith, but the details vary by state and country, so check the rules where you live.

Step 7: Build Readiness With Training and a Workplace Plan

Reading about CPR helps, but hands-on practice builds the muscle memory and confidence that make you act under pressure. A good course lets you work on manikins, practice with a training AED, and get feedback on your depth and rate.

Choose the course that fits your role:

Healthcare workers: BLS (Basic Life Support) certification, which covers team-based resuscitation, high-quality compressions, and advanced airway basics.
Workplace coordinators and general responders: CPR and AED training, often paired with First Aid so staff can handle bleeding, choking, and other emergencies.

Certifications typically need renewal every two years, but policies vary, so confirm the current requirement with the issuing organization before you plan your schedule.

If you coordinate workplace safety

Training people is only half the plan. Make sure the equipment and the process work too:

Map every AED location and share the map with staff and new hires.
Check pad and battery expiry dates on a set schedule, and note them in a log.
Post clear signage so AEDs can be found quickly, including from a distance.
Run periodic response drills that cover calling, retrieving the AED, starting compressions, and guiding EMS to the scene.
Make sure enough trained people are on every shift, including nights and weekends.

A drill often reveals simple problems, such as a locked cabinet or an unclear address for dispatchers, that you can fix before a real emergency.

Turning Recognition Into a Reliable Skill

Recognizing cardiac arrest comes down to two observations: the person is unresponsive, and their breathing is absent or abnormal. Follow that with an immediate call, chest compressions, and an AED, and you give someone their best chance. After you finish reading this guide, the next step is practice. Enrolling in a certified CPR or BLS course turns this knowledge into a skill you can rely on.

Don't wait until an emergency happens. Equip yourself with life-saving CPR skills that could make all the difference when seconds count. Register for a certification class today and gain the confidence to respond when someone needs help most.