Clinical Subject Page
Cardic Arrest
Also called
Sudden cardiac arrest
ICD-10
I46.9
Specialty
Cardiology
Onset
Acute
Reviewed
July 2026
On This Page
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OverviewOverview
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Etiology & Risk FactorsEtiology & Risk Factors
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PathophysiologyPathophysiology
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Clinical PresentationClinical Presentation
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Recognition of Cardiac Arrest (Initial Assessment)Recognition of Cardiac Arrest (Initial Assessment)
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InvestigationsInvestigations
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DiagnosisDiagnosis
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ManagementManagement
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ComplicationsComplications
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PrognosisPrognosis
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Key Points / Clinical PearlsKey Points / Clinical Pearls
Overview
Cardiac arrest is the sudden cessation of cardiac function and blood circulation, resulting in loss of consciousness, apnea (or abnormal gasping), and absence of a pulse. It is a medical emergency requiring immediate CPR and, if indicated, defibrillation to improve survival.
Teaching point
Cardiac arrest ≠ myocardial infarction (heart attack). A heart attack can cause cardiac arrest, but they are different conditions.
Etiology & Risk Factors
Cardiac Causes
- Coronary artery disease (most common in adults)
- Acute myocardial infarction
- Malignant arrhythmias (VF, pulseless VT)
- Cardiomyopathy
- Severe heart failure
Noncardiac Causes (Reversible Causes)
5 Hs
- Hypovolemia
- Hypoxia
- Hydrogen ion (acidosis)
- Hyperkalemia/Hypokalemia
- Hypothermia
5 Ts
- Tension pneumothorax
- Cardiac tamponade
- Toxins
- Thrombosis (pulmonary embolism)
- Thrombosis (coronary)
Other causes include:
- Hypoglycemia
- Hypocalcemia
- Hypomagnesemia
- Anaphylaxis
- Severe asthma
Pathophysiology
Cardiac arrest occurs when the heart suddenly stops pumping blood effectively, causing cessation of systemic circulation.
Mechanism
- Loss of effective cardiac mechanical activity
- No cardiac output
- No blood flow to vital organs
- Rapid cerebral hypoxia and ischemia
- Irreversible brain injury begins within minutes if circulation is not restored
Simple Flow
Underlying cardiac/noncardiac cause → Heart stops pumping effectively → No cardiac output → No oxygen delivery to organs → Brain ischemia → Organ failure → Death (without prompt CPR/defibrillation)
Clinical Presentation
Symptoms/Signs
- Sudden collapse
- Unresponsiveness
- No normal breathing (or gasping)
- No palpable pulse
Important Note
Cardiac arrest = no pulse + no normal breathing + unconsciousness.
Recognition of Cardiac Arrest (Initial Assessment)
Step 1: Ensure Scene Safety
- Make sure the environment is safe for you and the patient.
Step 2: Check Responsiveness
- Tap the patient’s shoulders.
- Shout: “Are you okay?”
- If there is no response, suspect cardiac arrest.
Step 3: Call for Help
- Activate the emergency response system.
- Ask someone to bring an AED/defibrillator immediately.
Step 4: Check Breathing
- Look for normal breathing.
- Agonal gasps are NOT normal breathing and should be treated as cardiac arrest.
Step 5: Check Pulse (Healthcare Providers)
- Check a central pulse (carotid or femoral).
- Spend no more than 10 seconds checking.
- If no pulse or unsure → start CPR immediately.
Step 6: Start High-Quality CPR
- Begin chest compressions immediately.
- Attach an AED/defibrillator as soon as it is available.
Signs Suggesting Cardiac Arrest
- Sudden collapse
- Unresponsiveness
- No normal breathing or only gasping
- No palpable central pulse
- Pale or cyanotic skin
- Dilated pupils (late sign)
Investigations
Laboratory
- CBC
- Electrolytes
- Renal & liver function
- Troponin
- BNP/NT-proBNP
- Arterial blood gas
- Serum lactate
- Coagulation profile
ECG
- Acute MI changes
- Arrhythmias
Imaging
- Echocardiography (first-line)
- Chest X-ray
- Coronary angiography (if ACS suspected)
Hemodynamic Monitoring
- Arterial line
- Central venous access
- Pulmonary artery catheter (selected patients)
Diagnosis
Diagnosis is based on:
- Clinical evidence of shock
- SBP <90 mmHg (or need for vasopressors)
- Signs of end-organ hypoperfusion
- Elevated lactate
- Echocardiographic evidence of severe cardiac dysfunction
- Identification of the underlying cardiac cause
Management
1. Basic Life Support (BLS)
- Recognize cardiac arrest and activate the emergency response system.
- Start high-quality CPR immediately.
- Apply an AED (Automated External Defibrillator) as soon as available.
- Defibrillate immediately if a shockable rhythm is detected.
2. Advanced Cardiac Life Support (ACLS)
Step 1
- Continue high-quality CPR.
- Attach a cardiac monitor/defibrillator.
- Obtain IV/IO access.
Step 2: Identify the Rhythm
A. Shockable Rhythms
- Ventricular fibrillation (VF)
- Pulseless ventricular tachycardia (pVT)
Management
- Immediate defibrillation
- Resume CPR for 2 minutes
- Epinephrine 1 mg IV/IO after the second unsuccessful shock, then every 3–5 minutes
- Amiodarone 300 mg IV/IO (or lidocaine) after the third unsuccessful shock
B. Nonshockable Rhythms
- Pulseless electrical activity (PEA)
- Asystole
Management
- Do NOT defibrillate
- Continue CPR
- Epinephrine 1 mg IV/IO immediately, then every 3–5 minutes
- Search for and treat reversible causes (5 Hs & 5 Ts)
3. Airway Management
- Minimize interruptions to CPR.
- Consider advanced airway (endotracheal tube or supraglottic airway) if needed.
- Confirm placement with continuous waveform capnography.
- Once an advanced airway is in place:
- Continue continuous chest compressions.
- Give 1 breath every 6 seconds.
4. Post-Resuscitation Care (After ROSC)
- Secure the airway and optimize oxygenation/ventilation.
- Maintain hemodynamic stability.
- Consider PCI if a cardiac cause (e.g., STEMI) is suspected.
- Temperature control.
- Treat seizures if present.
- Monitor for organ dysfunction and neurological recovery.
Complications
- Anoxic-ischemic encephalopathy (brain injury) (most important complication)
- Neurological dysfunction
- Ischemic cardiomyopathy
- Acute kidney injury (AKI)
- Shock liver
- Multiorgan dysfunction syndrome (MODS)
- Seizures
- Coma, persistent vegetative state, or brain death (in severe cases)
Prognosis
- Prognosis depends mainly on:
- Time to CPR
- Time to defibrillation (for shockable rhythms)
- Duration of anoxia
- Presence of return of spontaneous circulation (ROSC)
- Early CPR and early defibrillation significantly improve survival and neurological outcomes.
- Anoxia lasting >3–5 minutes is commonly associated with permanent brain injury.
- Patients who achieve ROSC require comprehensive post-resuscitation care to optimize recovery.