Cardiac Arrest

What is cardiac arrest?

Cardiac arrest is a sudden, life-threatening emergency in which the heart abruptly stops beating effectively. When this happens, the heart can no longer pump blood to the brain, lungs, and other organs. Within seconds, the person loses consciousness, and without immediate help, cardiac arrest is fatal in a matter of minutes. In medical coding systems, this condition is classified under ICD-10 code I46.9, which refers to cardiac arrest of unspecified cause.

To understand what is cardiac arrest, it helps to know how the heart normally works. The heart relies on an internal electrical system that tells it when and how to beat. In most cases of cardiac arrest, this electrical system malfunctions, causing a dangerously abnormal heart rhythm (called an arrhythmia). The most common of these is ventricular fibrillation, a chaotic rhythm in which the heart’s lower chambers quiver instead of pumping. In other cases, the heart’s electrical activity may become too slow or stop entirely.

Cardiac arrest is often confused with a heart attack, but they are different problems. A heart attack (myocardial infarction) happens when blood flow to part of the heart muscle is blocked, usually by a clot in a coronary artery. The heart typically keeps beating during a heart attack. Cardiac arrest, by contrast, is an electrical problem that stops the heartbeat itself. A heart attack can trigger cardiac arrest, and it is one of its most common causes, but the two terms are not interchangeable.

Cardiac arrest can affect anyone, at any age, although it is more common in adults with underlying heart disease. It can also occur in younger people, sometimes due to inherited heart conditions, structural heart abnormalities, or, rarely, a strong blow to the chest. Men are affected somewhat more often than women, and the risk generally increases with age.

Symptoms of cardiac arrest

Cardiac arrest symptoms appear suddenly and are dramatic. Unlike many medical conditions that develop gradually, cardiac arrest usually strikes without much warning, and the person collapses within seconds. The hallmark signs are:

• Sudden collapse — the person falls or slumps over without warning.
• Loss of consciousness — the person does not respond to voice, touch, or shaking.
• No normal breathing — breathing stops, or the person makes only occasional gasping sounds (known as agonal breathing), which is not effective breathing.
• No pulse — the heart is not pumping blood, so no pulse can be felt.

In some people, warning symptoms occur in the minutes, hours, or even days before the arrest. These are not present in every case, but they can include:

• Chest pain, pressure, or discomfort
• Shortness of breath
• Palpitations (a racing, pounding, or fluttering heartbeat)
• Unexplained dizziness or lightheadedness
• Fainting or near-fainting, especially during physical activity
• Unusual fatigue or weakness

How symptoms appear can differ depending on the underlying cause. When cardiac arrest is triggered by a heart attack, chest pain or pressure often comes first. When it results from a primary rhythm disturbance, such as ventricular fibrillation caused by an inherited electrical disorder, the collapse may be truly instantaneous, with no warning at all. In hospital settings, monitored patients may show a deteriorating heart rhythm before the arrest, which is one reason continuous monitoring is used for high-risk patients.

It is important to understand that once cardiac arrest occurs, the person cannot call for help or describe symptoms. Recognition depends entirely on bystanders. A person who has collapsed, is unresponsive, and is not breathing normally should be treated as being in cardiac arrest until proven otherwise.

Causes and risk factors

Cardiac arrest causes fall broadly into two groups: problems with the heart itself and external factors that disrupt the heart’s rhythm or function.

Heart-related causes

• Coronary artery disease — narrowing of the arteries that supply the heart muscle is the most common underlying condition in adults. A heart attack caused by a blocked artery can trigger a fatal arrhythmia.
• Cardiomyopathy — disease of the heart muscle, in which the heart becomes enlarged, thickened, or stiff, making dangerous rhythms more likely.
• Arrhythmias and inherited electrical disorders — conditions such as long QT syndrome or Brugada syndrome affect the heart’s electrical signaling and can cause sudden arrest, sometimes in otherwise healthy young people.
• Heart failure — a weakened heart is more prone to life-threatening rhythm disturbances.
• Heart valve disease and congenital heart defects — structural abnormalities present from birth or acquired later in life can increase risk.
• Myocarditis — inflammation of the heart muscle, often following a viral infection.

Non-cardiac causes

• Severe blood loss or severe lack of oxygen — for example, from major trauma, drowning, or choking.
• Electrolyte imbalances — abnormal blood levels of potassium, magnesium, or other minerals that the heart’s electrical system depends on.
• Drug effects and overdose — certain medications, recreational drugs, and stimulants can provoke fatal arrhythmias.
• Electrocution — electrical injury can disrupt the heart’s rhythm.
• Pulmonary embolism — a large blood clot in the lungs can cause sudden circulatory collapse.
• Commotio cordis — a rare event in which a blunt blow to the chest at a precise moment in the heartbeat triggers arrest, seen mostly in young athletes.

Risk factors

Factors that raise the likelihood of cardiac arrest largely overlap with those for heart disease in general. They include a previous heart attack or a previous episode of cardiac arrest, a family history of sudden cardiac death or inherited heart conditions, smoking, high blood pressure, high cholesterol, diabetes, obesity, physical inactivity, heavy alcohol use, and use of stimulant drugs. Older age and male sex are also associated with higher risk, although cardiac arrest can occur in anyone.

Diagnosis

Cardiac arrest diagnosis happens in two stages: recognizing the arrest itself in the emergency moment, and, if the person survives, identifying what caused it.

Recognizing the arrest

In the emergency setting, cardiac arrest is a clinical diagnosis made rapidly at the scene. Rescuers and medical teams confirm it by finding a person who is unresponsive, has no normal breathing, and has no detectable pulse. When an automated external defibrillator (AED) or hospital monitor is attached, it records the heart’s electrical rhythm. This shows whether the heart is in ventricular fibrillation, ventricular tachycardia (a very fast, dangerous rhythm), asystole (no electrical activity, often called a flatline), or pulseless electrical activity (electrical signals without an effective heartbeat). Identifying the rhythm guides immediate treatment.

Finding the cause after survival

For people who survive cardiac arrest, doctors carry out a thorough evaluation to find the underlying cause and reduce the risk of another event. Tests may include:

• Electrocardiogram (ECG or EKG) — a recording of the heart’s electrical activity, which can reveal a heart attack, rhythm disorders, or signs of inherited electrical conditions.
• Blood tests — to check for heart muscle damage (cardiac enzymes such as troponin), electrolyte levels, thyroid function, and evidence of drug effects.
• Echocardiogram — an ultrasound scan of the heart that shows how well the heart muscle and valves are working and measures the heart’s pumping strength.
• Coronary angiography — an imaging procedure in which dye is injected into the coronary arteries to look for blockages, often performed urgently if a heart attack is suspected.
• Cardiac MRI or CT scanning — detailed imaging that can detect scarring, inflammation, or structural abnormalities of the heart.
• Electrophysiology study — a specialized test in which thin tubes (catheters) are guided into the heart to map its electrical system and identify sources of abnormal rhythms.
• Genetic testing — in selected cases, especially in younger survivors or when an inherited condition is suspected, genetic testing may be offered to the patient and sometimes to family members.

Because some causes of cardiac arrest run in families, doctors may also recommend screening for close relatives of people who have experienced an unexplained arrest or sudden cardiac death.

Treatment options

Cardiac arrest treatment is unlike treatment for most other conditions: there is no role for watchful waiting during the arrest itself, because survival depends on action within minutes. Treatment can be divided into emergency care during the arrest, hospital care afterward, and long-term measures to prevent recurrence.

Emergency treatment

• Cardiopulmonary resuscitation (CPR) — chest compressions, with or without rescue breaths, keep some blood flowing to the brain and heart until advanced help arrives. Immediate bystander CPR is one of the most important factors influencing survival.
• Defibrillation — an electric shock delivered by an AED or hospital defibrillator can stop ventricular fibrillation or ventricular tachycardia and allow the heart’s normal rhythm to resume. Not all arrest rhythms are shockable, which is why the device analyzes the rhythm first.
• Advanced life support — emergency teams may give medications such as epinephrine (adrenaline) and antiarrhythmic drugs, secure the airway to support breathing, and treat reversible causes such as severe electrolyte imbalance.

Hospital care after resuscitation

People who regain a heartbeat after cardiac arrest are usually cared for in an intensive care unit. Care commonly includes support for breathing and blood pressure, careful management of body temperature (in some cases, controlled temperature management to help protect the brain), urgent treatment of the underlying cause — for example, opening a blocked coronary artery with a catheter procedure — and close monitoring for complications affecting the brain, kidneys, and other organs.

Preventing another cardiac arrest

Long-term treatment depends on the cause identified. Options your doctor may discuss include:

• Medications — such as beta blockers or antiarrhythmic drugs to stabilize the heart’s rhythm, and medicines to treat coronary artery disease, heart failure, or high blood pressure.
• Implantable cardioverter-defibrillator (ICD) — a small device placed under the skin, connected to the heart, that continuously monitors the rhythm and delivers a shock automatically if a dangerous arrhythmia occurs. ICDs are often recommended for survivors of cardiac arrest who remain at risk.
• Catheter ablation — a procedure that uses thin tubes guided into the heart to destroy small areas of tissue responsible for abnormal rhythms.
• Coronary procedures and surgery — angioplasty with stenting (opening a narrowed artery with a small balloon and mesh tube) or coronary artery bypass surgery may be needed when blocked arteries are the underlying problem. Surgery may also be considered for certain valve or structural heart conditions.
• Lifestyle and risk-factor management — stopping smoking, managing blood pressure, cholesterol, and diabetes, and following a heart-healthy diet and activity plan as advised by the care team.

Ongoing care after cardiac arrest is typically coordinated by heart specialists. At Acibadem, for example, this condition is evaluated and managed within the Cardiology Department, where cardiologists and electrophysiologists (heart rhythm specialists) plan long-term follow-up.

Living with cardiac arrest and outlook

The outlook after cardiac arrest varies widely and depends heavily on how quickly effective treatment began, the underlying cause, the heart rhythm at the time of arrest, and the person’s overall health. Sadly, many out-of-hospital cardiac arrests are not survived, largely because help does not arrive quickly enough. When bystanders start CPR immediately and a defibrillator is used early, the chances of survival improve considerably, though no outcome can ever be guaranteed.

Survivors of cardiac arrest may face a recovery period that involves more than the heart. Because the brain is very sensitive to a lack of oxygen, some survivors experience problems with memory, concentration, or mood. These effects range from mild and temporary to more lasting, and rehabilitation programs — including cardiac rehabilitation, physical therapy, and neuropsychological support — can help many people regain function over time.

Emotional recovery matters as well. Anxiety, depression, and fear of another event are common among survivors and their families. Talking openly with the care team, and seeking counseling or support groups when needed, is a normal and helpful part of recovery. Family members who witnessed the arrest may also benefit from support.

For people living with an ICD, regular device checks are part of follow-up care, and doctors provide guidance about activities, driving regulations (which vary by country), and what to do if the device delivers a shock. Many survivors are able to return to work, exercise, and daily life, though the pace and extent of recovery differ from person to person. Honest, ongoing communication with the cardiology team helps set realistic expectations.

Frequently asked questions

What is cardiac arrest in simple terms?

Cardiac arrest means the heart suddenly stops beating effectively, so blood stops flowing to the brain and body. The person collapses, loses consciousness, and stops breathing normally within seconds. It is a medical emergency that requires immediate CPR and defibrillation, because without treatment it is fatal within minutes.

Is cardiac arrest the same as a heart attack?

No. A heart attack is a circulation problem — a blocked artery cuts off blood supply to part of the heart muscle, and the heart usually keeps beating. Cardiac arrest is an electrical problem in which the heartbeat itself stops. A heart attack can lead to cardiac arrest, which is one reason chest pain should always be taken seriously, but the two conditions are treated differently.

What are the warning signs of cardiac arrest?

Cardiac arrest often occurs with little or no warning. However, some people experience chest discomfort, shortness of breath, palpitations, dizziness, or fainting in the days or hours beforehand. Once the arrest occurs, the key signs are sudden collapse, unresponsiveness, absence of normal breathing, and no pulse. Occasional gasping sounds are not normal breathing and should not delay CPR.

Can you survive cardiac arrest?

Yes, survival is possible, especially when CPR begins immediately and a defibrillator is used within the first minutes. Survival depends on many factors, including how quickly help was given, the underlying cause, and the person’s overall health. Every minute without treatment reduces the chance of survival, which is why bystander action is so important. No one can guarantee an outcome in any individual case.

Can the heart heal after cardiac arrest?

Recovery depends on the cause and on how much damage occurred to the heart and brain. If the underlying problem — such as a blocked artery or an electrolyte imbalance — is corrected, heart function may recover partly or substantially in many cases. Some survivors have lasting heart weakness or neurological effects, while others regain good function. Doctors assess this over time with tests such as echocardiograms.

How is a future cardiac arrest prevented?

Prevention depends on the cause identified after the first event. Options often include medications to stabilize the heart’s rhythm and treat heart disease, an implantable cardioverter-defibrillator (ICD) that automatically shocks dangerous rhythms, catheter ablation, procedures or surgery to restore blood flow, and careful management of risk factors such as smoking, blood pressure, and cholesterol. Your doctor tailors the plan to your specific situation.

What should I do if I see someone collapse?

If a person collapses, is unresponsive, and is not breathing normally, call your local emergency number immediately, start chest compressions (push hard and fast in the center of the chest), and send someone to find the nearest AED. Use the AED as soon as it arrives and follow its voice instructions. Continue CPR until emergency responders take over. Acting quickly, even imperfectly, is far better than doing nothing.

When to see a doctor

Cardiac arrest itself is always an emergency: if someone is unresponsive and not breathing normally, call your local emergency number immediately and start CPR. Do not wait to see whether the person recovers on their own.

Seek urgent medical attention if you or someone near you experiences any of the following red-flag warning signs:

• Chest pain, pressure, tightness, or squeezing, especially if it spreads to the arm, jaw, neck, or back
• Sudden severe shortness of breath at rest or with minimal effort
• Fainting or collapse, particularly during exercise or without an obvious explanation
• A racing, pounding, or very irregular heartbeat accompanied by dizziness, weakness, or near-fainting
• Sudden unexplained dizziness or lightheadedness that does not quickly resolve
• Any warning symptoms in a person with a previous heart attack, known heart disease, or a family history of sudden cardiac death

Even if symptoms pass, they should not be ignored. Fainting during exertion, unexplained palpitations, or a family history of sudden death at a young age warrant a non-urgent but prompt evaluation by a doctor, who may refer you to a cardiologist for rhythm testing and heart imaging. Early evaluation can identify treatable conditions before they lead to a life-threatening event.