Introduction
Cardiac arrest means the heart suddenly stops pumping effectively—there is no pulse, breathing stops or becomes ineffective, and the person collapses unconscious. It is an extreme emergency; brain injury and death can occur within minutes. Immediate CPR and rapid defibrillation when indicated greatly improve survival.
It is not the same as a heart attack, although a heart attack is a major trigger. In a heart attack a coronary artery is blocked and muscle is damaged; in arrest the electrical or pumping system fails and circulation ceases. Ventricular fibrillation is a common pathway, but not every arrhythmia is cardiac arrest.
Community bystander CPR in homes, workplaces, and public spaces saves lives. Warning may be absent—sudden collapse, unresponsiveness, and no breathing—or there may be preceding chest pain, breathlessness, dizziness, or palpitations.
This page covers definition, risks, symptoms, emergency response, later testing and treatment, prevention, and living after survival. In a real emergency, call local emergency services and start CPR at once. This text is educational, not a substitute for emergency care.
Overview
In sudden cardiac arrest, effective cardiac output falls toward zero. The most common shockable rhythms are ventricular fibrillation and pulseless ventricular tachycardia; a defibrillator may restore an organized rhythm.
Other presentations include asystole (electrical silence) or pulseless electrical activity—shock utility differs, but high-quality CPR remains essential.
After return of circulation, hospitals search for causes and use medicines, angioplasty or bypass, ablation, and implantable defibrillators to prevent recurrence. Prevention means controlling heart-disease risk and acting early on warning symptoms.
- Sudden pump failure → no pulse, unconsciousness, absent or ineffective breathing
- Different from heart attack or everyday arrhythmia—though those can cause arrest
- Emergency priorities: call for help + high-quality CPR + rapid AED/defibrillation
- Every minute of delay lowers survival odds
- Risk factors include prior heart disease, smoking, hypertension, diabetes, and some drugs
- Survivors need cause investigation and secondary prevention
- Community CPR training saves lives
What happens in the body
Coordinated electrical signals and oxygenated blood flow keep the heart pumping. Coronary blockage, severe arrhythmia, hypoxia, electrolyte imbalance, or major trauma can collapse that coordination so the ventricles no longer eject blood.
When brain and organ perfusion stop, consciousness is lost within seconds to minutes. CPR provides temporary circulation; defibrillation can “reset” a chaotic shockable rhythm toward an effective beat.
- Electrical chaos (for example VF) → ineffective pumping
- Acute ischemia or heart attack can trigger arrest
- Oxygen, electrolyte, or acid–base failure can stop the pump
- Zero blood flow → brain injury begins within minutes
- CPR sustains temporary flow; AED delivers shocks for shockable rhythms
- After ROSC, organ protection and cause-directed therapy are required
Signs and symptoms
Arrest itself is sudden and dramatic. Warning symptoms may precede some events:
- Sudden collapse and unresponsiveness
- Absent pulse
- No breathing or only abnormal gasping
- No response to voice or touch; eyes do not open purposefully
- Pale or bluish skin (cyanosis)
- Preceding chest pain or pressure
- Preceding severe shortness of breath
- Preceding palpitations or racing heartbeat
- Preceding dizziness, blackouts, or near-fainting
- Preceding extreme fatigue or weakness
- Vomiting or nausea in some cases
- Agitation or confusion as an uncommon warning
- Seizure-like movements from oxygen deprivation in some collapses
- Direct collapse with no warning—common in many cases
Causes and risk factors
Arrest is a final common pathway; underlying drivers and risks include:
- Coronary artery disease and acute heart attack
- Dangerous arrhythmias (ventricular fibrillation or tachycardia)
- Heart failure or cardiomyopathy
- Personal or family history of heart disease
- Smoking, high blood pressure, high cholesterol, diabetes
- Obesity and long-term physical inactivity
- Heavy alcohol use; cocaine, amphetamines, and other stimulant drugs
- Very low or very high blood potassium or magnesium
- Male sex and increasing age raise risk in population studies
- Severe respiratory failure, major trauma, or drowning
Diagnosis and evaluation
At the scene, diagnosis is clinical—unresponsive with no breathing or pulse. After survival, hospitals look for causes:
- Immediate assessment: responsiveness, breathing, carotid pulse; start CPR
- ECG/monitor: identify VF, VT, asystole, or PEA
- Blood tests: electrolytes, cardiac markers, blood gases, toxins or drug levels as indicated
- Echocardiogram and chest X-ray
- Coronary angiogram when ischemia or blockage is suspected
- Electrophysiology study in selected arrhythmia cases
- Ejection fraction and structural heart assessment
- Brain and organ injury assessment after return of circulation
Treatment and management
First restore life; then treat the cause and prevent recurrence. Do not delay CPR while waiting for equipment:
- Immediate high-quality CPR (chest compressions and rescue breaths as trained)
- Rapid shocks with an AED or defibrillator for shockable rhythms
- Advanced life support: airway, medicines, intravenous or intraosseous access
- Cause-directed care: angioplasty/stenting or bypass when coronary blockage is found
- Antiarrhythmic and other medicines to stabilize rhythm and blood pressure
- Implantable cardioverter–defibrillator (ICD) when recurrence risk remains high
- Radiofrequency ablation for selected arrhythmia substrates
- Corrective heart surgery for structural problems when indicated
- Post-arrest intensive care including temperature management and organ support
- Risk-factor control: stop smoking; treat blood pressure, sugar, and cholesterol
Prevention, self-care, and lifestyle
Not every condition is fully preventable, but the steps below may lower risk or recurrence:
- Measure and control blood pressure, diabetes, and cholesterol regularly
- Stop smoking and illicit stimulants; limit alcohol
- Stay physically active and maintain a healthy weight
- Seek urgent cardiology care for chest pain, unexplained syncope, or abnormal palpitations
- Discuss screening if there is a family history of sudden death
- Encourage family members to learn CPR and AED use
- Take prescribed heart medicines consistently—do not stop them yourself
Possible complications
Delay, missed care, or unsafe self-medication can raise the chance of complications in some cases:
- Permanent hypoxic brain injury
- Death—especially when treatment is delayed
- Multi-organ failure (kidney, liver) after prolonged arrest
- Recurrent arrest or life-threatening arrhythmia
- Rib fractures or chest wall pain from CPR (acceptable relative to saving life)
- Long-term neurologic, cognitive, or psychological effects
- Family trauma and caregiving strain
When to see a doctor or seek emergency care
Seek prompt medical advice or emergency care if any of the following apply—it is safer not to wait and see:
- Anyone unconscious without normal breathing—call emergency services and start CPR now
- Severe chest pain, especially with pain into an arm or jaw
- Sudden severe breathlessness, blackouts, or near-collapse
- Rapid or irregular palpitations with weakness
- New warning symptoms after prior heart attack or arrest
- Repeated ICD shocks or unexplained fainting
- Chest fluttering or near-fainting after stimulant drug use
Living with the condition
After survival, cardiac rehabilitation, graded activity, and psychological support matter. Discuss work and driving rules if an ICD is present.
Share medicine lists, follow-up dates, and an emergency plan with family. Avoid smoking and stimulants; keep a symptom diary.
Fear and anxiety are common—support groups or counseling help. If a home AED is available, train household members to use it.
Frequently asked questions
Are cardiac arrest and heart attack the same?
No. A heart attack blocks blood flow to heart muscle; arrest means the pump itself stops. A heart attack can cause arrest, but they are different events.
How does arrhythmia differ from arrest?
Arrhythmia means an abnormal rhythm—many people remain conscious. Arrest means no effective pump, no pulse, and unconsciousness requiring CPR.
What should I do first?
Call emergency services, start chest-compression CPR, and bring a nearby AED. Even without formal training, continuous hard-and-fast compressions help.
Why is defibrillation urgent?
In VF or pulseless VT, a shock can reset the rhythm so the heart can pump again. Delay sharply reduces success.
Can it happen again after survival?
Risk remains. Treating the cause, medicines, and an ICD when indicated reduce recurrence—regular follow-up is essential.
Can cardiac arrest be prevented?
Not every case, but controlling heart risk factors and acting on early warning symptoms prevents many events.
Important caution
This article is for general health education. It is not a substitute for emergency medical services.
If someone is unresponsive and not breathing normally, call for help immediately and begin CPR.
Risk-factor control, early symptom recognition, and community CPR skills can save lives.