Cardiac arrest is a sudden medical emergency in which the heart can no longer pump blood effectively to the brain and other vital organs. The latest U.S. resuscitation guidance continues to emphasize immediate recognition, emergency response, high-quality CPR and rapid use of an AED as the most important early actions.
The condition can happen without warning. A person may suddenly collapse, become unresponsive and stop breathing normally. In those moments, every minute matters. Fast action from someone nearby can help keep blood moving until emergency medical professionals arrive.
The American Heart Association released its latest comprehensive CPR and emergency cardiovascular care guidance in October 2025. The updated recommendations remain the current major U.S. guidance in 2026 and include updated recommendations for emergency response, defibrillation, advanced care and treatment after circulation returns.
What Is Cardiac Arrest?
Cardiac arrest happens when the heart suddenly loses its ability to pump blood effectively. The problem often involves the heart’s electrical system, which controls the rhythm and timing of each heartbeat.
When effective pumping stops, blood flow to the brain and other organs falls sharply. A person can lose consciousness within seconds.
Normal breathing may also stop. Some people produce occasional abnormal gasps. These gasps are not normal breathing and should not cause a bystander to delay CPR.
This makes cardiac arrest one of the most urgent medical emergencies. The condition requires immediate emergency assistance rather than observation or waiting for symptoms to improve.
There is also an important distinction between an arrest and a heart attack. A heart attack occurs when blood flow to part of the heart becomes blocked. An arrest involves the heart’s failure to maintain effective circulation. A heart attack can sometimes trigger an arrest, but they are not the same condition.
How the Heart Becomes Unable to Pump
The heart relies on electrical signals to coordinate its contractions.
Under normal circumstances, electrical activity moves through the heart in an organized pattern. This allows the chambers to contract and push blood through the lungs and the rest of the body.
During an arrest, that system can become severely disrupted.
Some cases involve ventricular fibrillation, in which the lower chambers of the heart quiver rather than producing an effective pumping action. Pulseless ventricular tachycardia is another dangerous rhythm that can prevent useful circulation.
Other cases involve asystole, which represents a lack of detectable electrical activity, or pulseless electrical activity, in which electrical activity exists but the heart does not produce an effective pulse.
The treatment depends on the rhythm and the cause. Defibrillation can treat certain shockable rhythms, while other forms require CPR, medications and treatment of the underlying problem.
What Causes Cardiac Arrest?
There is no single cause.
Heart-related conditions account for many cases, but an arrest can also develop because of severe problems involving breathing, circulation, metabolism, trauma or other medical emergencies.
Potential causes include:
- Coronary artery disease
- Heart attack
- Cardiomyopathy
- Heart failure
- Dangerous abnormal heart rhythms
- Certain inherited heart conditions
- Severe electrolyte disturbances
- Severe blood loss
- Respiratory failure
- Choking
- Drowning
- Drug toxicity or overdose
- Electrical injury
- Major trauma
- Severe allergic reactions
- Certain infections
- Other serious metabolic or medical emergencies
A person does not always know that a heart condition exists before an arrest occurs. Some people have an undiagnosed structural or electrical heart problem.
In other situations, the event develops from a sudden emergency outside the heart.
Can Cardiac Arrest Happen Without Warning?
Yes.
One of the defining features of cardiac arrest is its sudden nature. A person may be awake and functioning normally shortly before an event.
Some people experience symptoms from an underlying condition beforehand. These can include chest discomfort, shortness of breath, unusual weakness, dizziness, palpitations or fainting.
Those symptoms do not automatically mean an arrest will occur. They can have many possible causes.
However, sudden or severe symptoms should not be ignored. A person with serious chest discomfort, difficulty breathing, fainting or other alarming symptoms needs prompt medical evaluation.
What Are the Signs?
The most important signs are usually sudden and obvious.
A person experiencing cardiac arrest may:
- Collapse suddenly
- Become unconscious
- Fail to respond when spoken to or touched
- Stop breathing normally
- Produce occasional abnormal gasps
- Show no signs of normal circulation
The combination of unresponsiveness and abnormal or absent breathing should be treated as an emergency.
Bystanders should not spend valuable time trying to determine the exact cause. The priority is to activate emergency services and begin CPR.
What Should You Do When Someone Collapses?
The first few actions are simple but extremely important.
Check for Responsiveness
Tap the person and speak loudly.
If there is no normal response, check whether the person is breathing normally.
Do not delay emergency treatment while searching for a pulse if you are an untrained bystander. An unresponsive person who is not breathing normally should be treated as being in cardiac arrest.
Call 911
Call 911 immediately.
If another person is nearby, ask that person to make the call and locate an AED.
When alone with an adult who suddenly collapses, use a phone’s speaker function when possible. This allows you to communicate with the emergency dispatcher while beginning CPR.
Emergency dispatchers can provide instructions to help guide a bystander through the response.
Begin CPR
Start chest compressions as soon as possible.
For an adult, place your hands in the center of the chest and push hard and fast.
The recommended compression rate is 100 to 120 compressions per minute.
High-quality compressions help move blood through the body while rescuers work to restore effective circulation.
For an untrained person responding to a sudden adult collapse, Hands-Only CPR is an important option. It focuses on continuous chest compressions without rescue breaths.
People with appropriate CPR training may provide conventional CPR with compressions and breaths.
The most important point is not to wait.
Find and Use an AED
An automated external defibrillator, or AED, can analyze the heart rhythm and determine whether an electrical shock is appropriate.
These devices are designed for use outside hospitals, including by members of the public.
When an AED arrives, turn it on and follow its spoken or visual instructions.
The device guides the rescuer through pad placement and rhythm analysis. It will only recommend a shock when the detected rhythm meets the criteria for defibrillation.
Nobody should touch the person during rhythm analysis or while a shock is being delivered.
After the AED gives instructions to resume CPR, compressions should begin again.
Why Immediate CPR Matters
CPR does not always restart the heart. Its primary purpose during the initial response is to keep blood circulating until a defibrillator or advanced medical treatment can restore effective heart function.
The American Heart Association states that immediate CPR can double or triple the chance of survival after an arrest.
That is why bystander action matters so much.
Out-of-hospital events frequently happen before professional responders can reach the person. A nearby family member, coworker, friend, customer or stranger may therefore become the first person capable of starting lifesaving care.
The 2025 U.S. guidelines continue to emphasize early recognition and rapid intervention as essential parts of the response.
What Does an AED Actually Do?
An AED is not simply a machine that automatically restarts every stopped heart.
Its purpose is more specific.
The device examines the heart’s electrical rhythm. If it detects a rhythm that can respond to defibrillation, it recommends or delivers an electrical shock according to its design and instructions.
The shock can interrupt certain dangerous rhythms and give the heart an opportunity to resume an organized rhythm.
An AED cannot replace CPR. It works as part of a coordinated emergency response.
CPR should begin immediately when appropriate, while someone else retrieves the AED. Once the device is available, rescuers should follow its instructions.
Cardiac Arrest and Heart Attack Are Different
The terms are often used interchangeably in everyday conversation, but they describe different medical emergencies.
A heart attack occurs when blood flow through a coronary artery becomes blocked. The affected portion of the heart does not receive enough oxygen.
A person having a heart attack may remain conscious. Chest pressure, discomfort, sweating, nausea and shortness of breath can occur.
An arrest occurs when the heart suddenly loses effective pumping ability. The person usually becomes unresponsive and does not breathe normally.
The two conditions can be connected. A heart attack can damage heart tissue or interfere with electrical stability and trigger an arrest.
Still, treating them as the same condition can create confusion during an emergency.
How Common Is Cardiac Arrest in the U.S.?
Cardiac arrest remains a major public health emergency in the United States.
The American Heart Association estimates that more than 350,000 cardiac arrests occur outside hospitals in the U.S. each year.
The majority are fatal.
Recent U.S. data also show why immediate intervention remains a major focus of resuscitation efforts. Survival after EMS-treated adult out-of-hospital cardiac arrest has remained around 10% in recent national and international data summarized in the latest guidelines.
Hospital outcomes can be substantially different when an arrest occurs inside a medical facility, where trained staff, monitoring equipment, defibrillators and advanced treatment are immediately available.
The latest U.S. registry data cited in the 2025 guidelines recorded a hospital-discharge survival rate of 23.6% for adult in-hospital cardiac arrest in 2023.
These statistics describe large populations. They cannot determine what will happen to a particular person.
What Happens When EMS Arrives?
Emergency medical professionals take over the resuscitation process when they reach the scene.
Their care can include continued CPR, defibrillation, airway support, oxygen and ventilation management, medications, heart rhythm monitoring and intravenous or other forms of access.
They also look for reversible causes.
The exact treatment depends on the patient’s condition and the rhythm detected.
If circulation returns, the patient may require transport to a hospital for additional care. Restoring a heartbeat is only one stage of treatment.
What Happens After the Heart Starts Again?
A patient who regains circulation may still be critically ill.
During the arrest, the brain and other organs may have received inadequate blood flow and oxygen.
Doctors therefore monitor the patient’s circulation, breathing, neurological condition and other vital functions.
The cause of the event must also be identified whenever possible.
Hospital care can include electrocardiograms, laboratory testing, imaging, heart monitoring and specialized critical care.
The latest resuscitation recommendations include guidance for care after circulation returns, including management of oxygen, ventilation, blood pressure and temperature, along with evaluation for underlying causes.
Recovery can vary significantly between patients.
Some people recover quickly. Others require prolonged intensive care, rehabilitation or treatment for neurological and physical complications.
Who Is at Greater Risk?
Risk can increase with certain cardiovascular conditions and other serious medical problems.
Conditions associated with cardiovascular risk include coronary artery disease, high blood pressure, high cholesterol, diabetes and heart failure.
Smoking also increases cardiovascular risk.
Certain inherited conditions can increase the likelihood of dangerous heart rhythms. Some people may have a family history of sudden cardiac death or inherited heart disorders.
However, risk factors do not mean an arrest is inevitable.
Likewise, someone without known risk factors can still experience an unexpected emergency.
That uncertainty makes emergency preparedness important for everyone.
Can Cardiac Arrest Be Prevented?
Not every case can be prevented.
Still, many cardiovascular risk factors can be addressed.
Heart-health strategies include maintaining a healthy lifestyle, avoiding tobacco, staying physically active, managing blood pressure and cholesterol, controlling diabetes and following treatment plans for known cardiovascular conditions.
People with diagnosed heart conditions may need additional evaluation and monitoring.
Some patients with a high risk of life-threatening abnormal rhythms may qualify for an implantable cardioverter-defibrillator. This device can detect certain dangerous rhythms and deliver electrical therapy when needed.
The decision depends on an individual’s medical history and risk assessment.
What Makes the First Few Minutes So Important?
The body cannot tolerate prolonged interruption of blood flow to the brain and other organs.
That is why the sequence of emergency actions matters.
A person nearby can potentially:
- Recognize that the person is unresponsive and not breathing normally.
- Call 911.
- Start CPR.
- Locate an AED.
- Follow the AED instructions.
- Continue resuscitation until trained professionals take over.
Each step supports the next.
This coordinated approach is often described as a chain of survival. The 2025 guidelines use a unified chain of survival framework for cardiac arrest across different settings and age groups.
Cardiac Arrest in Children
Children can also experience sudden cardiac arrest, although the causes can differ from those commonly seen in adults.
Respiratory emergencies, choking, drowning and other serious conditions can contribute to pediatric arrests.
The latest U.S. resuscitation guidance includes pediatric-specific recommendations.
New research presented in 2025 also reinforced the importance of starting CPR quickly after a child’s arrest. The findings showed particularly strong associations between early bystander CPR and survival.
Adults caring for children can benefit from formal CPR training that includes infant and child techniques.
Why CPR Training Matters
Knowing what to do before an emergency occurs can make the response faster.
CPR courses teach people how to recognize an arrest, perform effective compressions and use an AED. Training can also cover differences in emergency response for adults, children and infants.
Hands-Only CPR gives untrained bystanders a straightforward way to respond to a sudden adult collapse.
The goal is not to make an ordinary person perform advanced medical care. The goal is to help bridge the critical period between the collapse and arrival of professional help.
The Latest U.S. Guidance in 2026
As of August 17, 2026, the 2025 American Heart Association CPR and emergency cardiovascular care guidelines remain the latest comprehensive U.S. resuscitation guidance.
The update represented the first full revision since 2020 and incorporated newer evidence across basic life support, advanced care, pediatric emergencies and post-arrest treatment.
The guidance continues to place strong emphasis on early recognition, high-quality CPR and timely defibrillation.
It also expands or updates recommendations for several special circumstances, including choking and suspected opioid overdose.
For the public, the central message remains straightforward: recognize the emergency, call 911, start CPR and use an AED as soon as one is available.
Final Takeaway
Understanding this emergency can help people respond rather than freeze when someone suddenly collapses. The condition can develop without warning, but immediate CPR and rapid defibrillation can provide a vital chance for survival before professional medical care arrives.
Have you learned CPR or ever seen an AED used during an emergency? Share your thoughts in the comments and stay informed about the latest verified health updates.