Cardiac Arrest

Overview

Cardiac arrest occurs when the heart's electrical system malfunctions, causing it to stop beating effectively. This differs from a heart attack, which is caused by blocked blood flow to the heart muscle. During cardiac arrest, the heart may quiver ineffectively (ventricular fibrillation) or stop beating altogether (asystole), preventing blood from circulating to the brain and other vital organs. Without immediate treatment, cardiac arrest leads to death within minutes.

Each year, more than 350,000 out-of-hospital cardiac arrests occur in the United States alone, with survival rates varying dramatically based on the speed and quality of emergency response. When CPR is performed immediately and defibrillation is provided within 3-5 minutes, survival rates can exceed 50%. However, for every minute that passes without CPR and defibrillation, the chance of survival decreases by 7-10%. This underscores the critical importance of public awareness, CPR training, and widespread availability of automated external defibrillators (AEDs).

Cardiac arrest can strike anyone at any age, though it's more common in older adults with underlying heart disease. It can occur during physical activity or at rest, and sometimes happens without warning in seemingly healthy individuals. The chain of survival - early recognition, early CPR, early defibrillation, and early advanced care - represents the critical steps needed to maximize survival chances. Understanding cardiac arrest, its warning signs, and how to respond can literally mean the difference between life and death.

Symptoms

Cardiac arrest often occurs suddenly, but some people may experience warning signs hours, days, or weeks before the event. Recognizing these symptoms and the signs of cardiac arrest itself is crucial for survival.

Warning Signs Before Cardiac Arrest

In the time leading up to cardiac arrest, individuals may experience:

• Shortness of breath - Often worsening with exertion or when lying flat
• Sharp chest pain - May radiate to arms, neck, jaw, or back
• Palpitations - Feeling of racing, fluttering, or pounding heart
• Irregular heartbeat - Skipped beats or abnormal rhythm sensations
• Weakness - Unusual fatigue or lack of energy
• Difficulty breathing - Even during rest or mild activities

Additional Warning Symptoms

• Arm swelling - May indicate heart failure leading to arrest
• Decreased heart rate - Bradycardia can precede certain types of arrest
• Dizziness or lightheadedness
• Nausea or vomiting
• Cold sweats
• Anxiety or feeling of impending doom

Signs of Cardiac Arrest

When cardiac arrest occurs, the person will show:

• Sudden collapse - Loss of consciousness
• No pulse - No detectable heartbeat
• Not breathing - Or only gasping (agonal breathing)
• Unresponsiveness - No response to shaking or shouting
• Loss of color - Skin becomes pale or blue-tinged

Agonal Breathing

Important to recognize:

• Gasping, snorting, or gurgling sounds
• Not normal breathing - requires CPR
• Occurs in about 40% of cardiac arrests
• May be mistaken for normal breathing
• Usually stops within minutes

Symptoms in Special Populations

Women

• More likely to have "atypical" symptoms
• Back or jaw pain
• Nausea and vomiting
• Extreme fatigue

Diabetics

• May have less chest pain due to neuropathy
• Shortness of breath may be primary symptom
• Confusion or altered mental state

Athletes

• Exercise-induced symptoms
• Chest pain during activity
• Unexplained decrease in performance
• Fainting during or after exercise

Causes

Cardiac arrest results from electrical problems in the heart that disrupt its pumping action. Understanding these causes helps identify at-risk individuals and guide prevention strategies.

Primary Electrical Problems

Ventricular Fibrillation (VF)

• Most common cause of sudden cardiac arrest
• Rapid, erratic electrical impulses
• Heart quivers instead of pumping
• No blood flow to body
• Requires immediate defibrillation

Ventricular Tachycardia (VT)

• Rapid heart rhythm originating in ventricles
• Can deteriorate into ventricular fibrillation
• May cause inadequate blood flow
• Pulseless VT requires defibrillation

Asystole

• Complete absence of electrical activity
• "Flatline" on monitor
• Often end-stage of other rhythms
• Poor prognosis

Pulseless Electrical Activity (PEA)

• Electrical activity without mechanical pumping
• Requires identifying underlying cause
• Not shockable rhythm

Underlying Heart Conditions

Coronary Artery Disease

• Most common underlying cause
• Plaque buildup in heart arteries
• Can trigger heart attack leading to arrest
• May cause scarring affecting electrical system

Cardiomyopathy

• Dilated cardiomyopathy: Enlarged, weakened heart
• Hypertrophic cardiomyopathy: Thickened heart muscle
• Arrhythmogenic right ventricular dysplasia: Fatty replacement of muscle
• All increase arrhythmia risk

Heart Valve Disease

• Severe aortic stenosis
• Mitral valve prolapse with regurgitation
• Prosthetic valve dysfunction

Congenital Heart Disease

• Structural abnormalities present from birth
• Repaired or unrepaired defects
• Higher risk in certain conditions

Electrical Abnormalities

Primary Electrical Diseases

• Long QT syndrome: Delayed repolarization
• Brugada syndrome: Genetic sodium channel disorder
• Catecholaminergic polymorphic VT: Exercise-induced arrhythmias
• Short QT syndrome: Rapid repolarization
• Wolff-Parkinson-White syndrome: Extra electrical pathway

Triggers and Precipitating Factors

Acute Events

• Heart attack: Acute coronary occlusion
• Pulmonary embolism: Blood clot in lungs
• Aortic dissection: Tear in aorta
• Cardiac tamponade: Fluid around heart

Metabolic Causes

• Electrolyte imbalances: Potassium, magnesium, calcium
• Severe acidosis: pH imbalance
• Hypoxia: Low oxygen levels
• Hypothermia: Core body temperature <90°F

Drugs and Toxins

• Cocaine or amphetamines
• Certain medications (antiarrhythmics, antipsychotics)
• Digitalis toxicity
• Carbon monoxide poisoning

Other Causes

• Commotio cordis: Blow to chest at vulnerable moment
• Drowning: Hypoxia-induced arrest
• Electrocution: Electrical injury to heart
• Severe trauma: Massive blood loss or cardiac injury
• Choking: Airway obstruction leading to hypoxia

Risk Factors

Understanding risk factors for cardiac arrest helps identify individuals who may benefit from preventive measures and closer monitoring.

Major Risk Factors

• Previous cardiac arrest or VF: Highest risk for recurrence
• Previous heart attack: Especially within first year
• Family history of sudden cardiac death: Genetic predisposition
• Ejection fraction <35%: Severe heart dysfunction
• Heart failure: Increases risk 6-9 fold

Cardiovascular Risk Factors

• Coronary artery disease: Present in 80% of sudden cardiac deaths
• Hypertension: Damages heart over time
• High cholesterol: Contributes to artery blockage
• Diabetes: Accelerates atherosclerosis
• Obesity: Strains cardiovascular system
• Metabolic syndrome: Cluster of risk factors

Lifestyle Factors

• Smoking: Doubles risk of sudden cardiac death
• Excessive alcohol: Can trigger arrhythmias
• Drug abuse: Particularly cocaine, amphetamines
• Physical inactivity: Weakens cardiovascular fitness
• Chronic stress: May trigger events
• Poor diet: High in saturated fats, low in nutrients

Age and Gender Factors

• Age: Risk increases with age
• Male gender: Higher risk, especially 45-75 years
• Post-menopausal women: Risk increases after menopause
• Young athletes: Risk with undiagnosed heart conditions

Medical Conditions

• Sleep apnea: Increases arrhythmia risk
• Chronic kidney disease: Electrolyte imbalances
• Thyroid disorders: Both hyper and hypothyroidism
• Inflammatory conditions: Myocarditis, sarcoidosis

Genetic and Congenital Factors

• Inherited arrhythmia syndromes
• Familial cardiomyopathies
• Congenital heart defects
• Genetic cholesterol disorders

Medications and Supplements

• Certain antiarrhythmic drugs (paradoxically)
• Some psychiatric medications
• Diuretics causing electrolyte imbalance
• Stimulant medications
• Some herbal supplements

Diagnosis

Diagnosis of cardiac arrest is clinical and must be made within seconds. Post-resuscitation evaluation focuses on identifying causes and preventing recurrence.

Immediate Recognition

Cardiac arrest diagnosis requires:

• Unresponsiveness: No response to verbal or physical stimuli
• Absent or abnormal breathing: Not breathing or only gasping
• No pulse: Check carotid artery for no more than 10 seconds

During Resuscitation

Cardiac Monitoring

• ECG rhythm identification
• Shockable rhythms (VF/VT) vs non-shockable (asystole/PEA)
• Continuous monitoring during CPR
• Response to interventions

Point-of-Care Testing

• Blood glucose levels
• Electrolyte assessment
• Blood gas analysis
• Point-of-care ultrasound (if available)

Post-Resuscitation Evaluation

Immediate Tests

• 12-lead ECG: Evidence of heart attack or arrhythmia
• Chest X-ray: Heart size, pulmonary edema, pneumothorax
• Blood tests:
  • Cardiac biomarkers (troponin)
  • Complete blood count
  • Comprehensive metabolic panel
  • Arterial blood gas
  • Lactate levels

Cardiac Catheterization

• Emergent if ST-elevation myocardial infarction
• Early catheterization for likely cardiac cause
• Identifies and treats coronary occlusions
• Assesses cardiac function

Echocardiography

• Assess left ventricular function
• Identify structural abnormalities
• Detect complications (tamponade, dissection)
• Guide ongoing management

Neurological Assessment

• CT scan: Rule out intracranial hemorrhage
• EEG: Detect seizures, assess brain function
• MRI: Evaluate hypoxic brain injury
• Neurological exam: Serial assessments

Identifying Underlying Causes

Additional Testing May Include

• CT angiography: Pulmonary embolism or aortic dissection
• Toxicology screen: Drug-induced arrest
• Thyroid function tests: Thyroid storm
• Cardiac MRI: Cardiomyopathy or infiltrative disease

Genetic Testing

Consider for:

• Young victims without obvious cause
• Family history of sudden death
• Suspected inherited arrhythmia syndrome
• Cardiomyopathy findings

Risk Stratification for Survivors

• Electrophysiology study: Assess arrhythmia risk
• Signal-averaged ECG: Late potentials
• T-wave alternans: Repolarization abnormalities
• Heart rate variability: Autonomic function
• Exercise testing: Inducible ischemia or arrhythmias

Treatment Options

Treatment of cardiac arrest requires immediate action following the chain of survival. Post-resuscitation care focuses on preventing recurrence and optimizing neurological recovery.

Immediate Response - Chain of Survival

1. Early Recognition and Call for Help

• Recognize unresponsiveness and abnormal breathing
• Call 911 immediately
• Request AED if available
• Put phone on speaker for dispatcher assistance

2. Early CPR

• Chest compressions:
  • Rate: 100-120 per minute
  • Depth: At least 2 inches (5 cm) for adults
  • Allow complete chest recoil
  • Minimize interruptions
• Rescue breathing:
  • 30:2 compression to breath ratio
  • 2 breaths after every 30 compressions
  • Hands-only CPR if untrained

3. Early Defibrillation

• Use AED as soon as available
• Follow voice prompts
• Continue CPR between shocks
• Critical within first 3-5 minutes

4. Advanced Life Support

• Intubation and mechanical ventilation
• IV/IO access for medications
• Advanced airway management
• Continuous cardiac monitoring

Medications During Cardiac Arrest

For All Rhythms

• Epinephrine: 1 mg IV/IO every 3-5 minutes
• Vasopressin: Alternative to epinephrine (less commonly used)

For Shockable Rhythms (VF/VT)

• Amiodarone: 300 mg IV/IO, then 150 mg
• Lidocaine: Alternative if amiodarone unavailable
• Magnesium: For torsades de pointes

Reversible Causes (H's and T's)

Treat specific causes:

• Hypovolemia: IV fluids, blood products
• Hypoxia: Ensure adequate ventilation
• Hydrogen ion (acidosis): Consider bicarbonate
• Hypo/hyperkalemia: Correct electrolytes
• Hypothermia: Active rewarming
• Tension pneumothorax: Needle decompression
• Tamponade: Pericardiocentesis
• Toxins: Specific antidotes
• Thrombosis: Thrombolytics if PE suspected

Post-Cardiac Arrest Care

Targeted Temperature Management

• Cool to 32-36°C for 24 hours
• Prevents secondary brain injury
• Continuous temperature monitoring
• Controlled rewarming

Hemodynamic Optimization

• Mean arterial pressure >65 mmHg
• Vasopressors as needed
• Fluid resuscitation
• Inotropic support if required

Ventilation Management

• Avoid hyperventilation
• Target normal oxygen and CO2 levels
• Lung protective strategies
• Gradual weaning when appropriate

Neuroprognostication

• Delayed at least 72 hours post-arrest
• Multimodal assessment
• Clinical examination
• EEG, imaging, biomarkers

Secondary Prevention

Implantable Cardioverter Defibrillator (ICD)

• For survivors at risk of recurrence
• Monitors heart rhythm continuously
• Delivers shock if VF/VT detected
• Can provide pacing support

Medications

• Beta-blockers: Reduce arrhythmia risk
• ACE inhibitors/ARBs: For heart failure
• Statins: If coronary disease
• Antiarrhythmic drugs: Selected cases
• Antiplatelet therapy: Post-MI or stent

Catheter Ablation

• For recurrent VT despite ICD
• Eliminates arrhythmia substrate
• May reduce ICD shocks

Rehabilitation

• Cardiac rehabilitation: Supervised exercise program
• Neurological rehabilitation: For brain injury
• Psychological support: PTSD, anxiety, depression
• Lifestyle modification: Risk factor reduction
• Family education: CPR training, emergency response

Prevention

Preventing cardiac arrest involves reducing cardiovascular risk factors, managing underlying conditions, and ensuring rapid response capability when events occur.

Primary Prevention

Lifestyle Modifications

• Heart-healthy diet:
  • Mediterranean or DASH diet
  • Limit saturated fats and cholesterol
  • Reduce sodium intake
  • Increase fruits and vegetables
• Regular exercise:
  • 150 minutes moderate intensity weekly
  • Or 75 minutes vigorous intensity
  • Strength training twice weekly
• Weight management: Maintain healthy BMI
• Smoking cessation: Complete abstinence
• Limit alcohol: Moderate consumption only
• Stress management: Meditation, yoga, counseling

Medical Management

• Blood pressure control: Target <130/80 mmHg
• Cholesterol management: Statins as indicated
• Diabetes control: HbA1c <7%
• Treat sleep apnea: CPAP therapy
• Manage arrhythmias: Appropriate medications

Screening High-Risk Individuals

Cardiac Screening

• Family history evaluation: Sudden death, early heart disease
• ECG screening: For athletes, family history
• Echocardiography: If structural disease suspected
• Exercise stress testing: For symptoms or risk
• Genetic testing: For inherited conditions

ICD Placement

Prophylactic ICD for:

• Ejection fraction ≤35% with symptoms
• Previous MI with EF ≤30%
• Certain genetic conditions
• Sustained VT with hemodynamic compromise

Community Preparedness

Public Access Defibrillation

• AEDs in public places
• Clear signage and accessibility
• Regular maintenance checks
• Registration with EMS

CPR Training

• Widespread public education
• School-based programs
• Workplace training
• Family member training for high-risk individuals
• Refresher courses every 2 years

Special Populations

Athletes

• Pre-participation screening
• ECG for competitive athletes
• Emergency action plans
• AEDs at sporting venues
• Trained medical personnel

Children and Adolescents

• Screen for family history
• Evaluate warning symptoms
• Genetic testing if indicated
• Activity restrictions when appropriate

Warning Sign Recognition

• Educate about prodromal symptoms
• Encourage early medical evaluation
• Emergency response planning
• Medical alert devices for high-risk
• Family notification systems

System-Level Prevention

• EMS optimization: Reduce response times
• Dispatcher-assisted CPR: Phone instructions
• First responder programs: Police, fire with AEDs
• Community awareness: Recognize and respond
• Quality improvement: Track outcomes, improve systems

When to See a Doctor

Recognizing warning signs and seeking timely medical attention can prevent cardiac arrest or improve outcomes.

Call 911 Immediately For

• Someone who is unconscious and not breathing normally
• Chest pain with shortness of breath, sweating, or nausea
• Sudden severe chest pain
• Fainting with chest pain or during exercise
• Rapid heartbeat with dizziness or near-fainting
• New confusion with chest discomfort

Seek Urgent Medical Care For

• Unexplained fainting episodes
• Palpitations lasting more than a few minutes
• Chest pain that comes and goes
• Unusual shortness of breath
• Swelling in legs with breathing difficulty
• Family member with sudden cardiac death

Schedule an Appointment For

• Family history of heart disease or sudden death
• Multiple cardiac risk factors
• Decreased exercise tolerance
• Persistent fatigue or weakness
• Irregular heartbeat sensations
• Concerns about heart health

Post-Cardiac Arrest Follow-Up

• All survivors need cardiology evaluation
• ICD consideration
• Medication optimization
• Cardiac rehabilitation referral
• Psychological support
• Family screening if inherited condition

Related Conditions

Several conditions are associated with increased risk of cardiac arrest or may be confused with it:

Cardiovascular Conditions

• Myocardial infarction (Heart Attack)
• Heart failure
• Atrial fibrillation
• Ventricular tachycardia
• Cardiomyopathy
• Coronary artery disease
• Valvular heart disease

Electrical Disorders

• Long QT syndrome
• Brugada syndrome
• Wolff-Parkinson-White syndrome
• Sick sinus syndrome

Other Emergency Conditions

• Pulmonary embolism
• Aortic dissection
• Stroke
• Seizure disorders
• Syncope (Fainting)

Risk Factor Conditions

• Hypertension
• Diabetes
• Hyperlipidemia
• Sleep apnea
• Chronic kidney disease

References

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