What are the different types of arrest?

Types of Cardiac Arrest

Cardiac arrest is categorized primarily by presenting rhythm, with the main types being shockable rhythms (ventricular fibrillation and pulseless ventricular tachycardia) and non-shockable rhythms (asystole and pulseless electrical activity). 1, 2

Classification by Presenting Rhythm

Shockable Rhythms

1. Ventricular Fibrillation (VF)

   • Characterized by chaotic, rapid electrical activity without coordinated ventricular contraction
   • Requires immediate defibrillation as the primary intervention
   • Better prognosis compared to non-shockable rhythms 3

2. Pulseless Ventricular Tachycardia (pVT)

   • Rapid ventricular rhythm without effective cardiac output
   • Also requires immediate defibrillation
   • Often seen in patients with underlying cardiac disease

Non-Shockable Rhythms

1. Asystole

   • Complete absence of electrical activity in the heart
   • Often referred to as "flatline"
   • Generally has worse prognosis than shockable rhythms
   • Primary treatment is high-quality CPR and epinephrine

2. Pulseless Electrical Activity (PEA)

   • Organized electrical activity visible on ECG without detectable pulse
   • Requires identification and treatment of underlying causes
   • Associated with poorer outcomes compared to shockable rhythms 3

Classification by Location

1. Out-of-Hospital Cardiac Arrest (OHCA)

   • Occurs in community settings
   • Often witnessed by bystanders
   • Survival depends heavily on early CPR and defibrillation
   • Approximately 350,000 cases annually in the US and Canada 1

2. In-Hospital Cardiac Arrest (IHCA)

   • Occurs in hospitalized patients
   • Estimated incidence of 3-6 per 1,000 hospital admissions 1
   • Often preceded by signs of clinical deterioration
   • Generally has better outcomes due to immediate medical response

Classification by Etiology

Cardiac Causes

• Primary arrhythmias
• Acute coronary syndromes
• Cardiomyopathies
• Structural heart disease
• Congenital heart defects (especially in pediatric patients) 4

Non-Cardiac Causes (Reversible Causes)

The American Heart Association organizes these into "H's and T's" 2, 5:

H's:

• Hypovolemia
• Hypoxia
• Hydrogen ion (acidosis)
• Hypo/Hyperkalemia and other electrolyte disorders
• Hypothermia

T's:

• Tension pneumothorax
• Tamponade (cardiac)
• Toxins/poisons/drugs
• Thrombosis (pulmonary embolism or coronary)

Special Circumstances in Cardiac Arrest

1. Post-Cardiac Surgery Arrest

   • Occurs in 1-8% of cardiac surgery cases 1
   • Unique considerations for resuscitation (resternotomy may be needed)
   • Common causes include tamponade, bleeding, and graft occlusion

2. Asthma-Related Arrest

   • Often due to severe bronchospasm and air trapping
   • Requires modified ventilation strategy with lower respiratory rates and increased expiratory time 1

3. Pediatric Arrest

   • More commonly due to respiratory causes rather than primary cardiac causes
   • Different compression techniques and depth requirements 1
   • Often related to channelopathies, cardiomyopathies, or myocarditis in cases of sudden cardiac arrest 4

Management Approach Based on Arrest Type

For Shockable Rhythms (VF/pVT)

1. Immediate defibrillation
2. High-quality CPR for 2 minutes
3. Establish IV/IO access
4. Administer epinephrine every 3-5 minutes
5. Consider amiodarone or lidocaine for refractory VF/pVT 2

For Non-Shockable Rhythms (Asystole/PEA)

1. High-quality CPR
2. Establish IV/IO access
3. Administer epinephrine every 3-5 minutes
4. Identify and treat reversible causes 1, 2

Emerging Approaches

For refractory cardiac arrest, particularly in cases of ventricular fibrillation unresponsive to standard treatment, extracorporeal membrane oxygenation (ECMO)-facilitated resuscitation has shown promising results with significantly improved survival to hospital discharge compared to standard ACLS treatment (43% vs 7%) 6.

Prognostic Considerations

Long-term survival varies significantly by presenting rhythm and etiology:

• 5-year survival: 73% for shockable rhythms vs 43% for non-shockable rhythms
• 5-year survival: 69% for cardiac etiology vs 45% for non-cardiac etiology 3

Understanding the specific type of cardiac arrest is crucial for implementing the appropriate resuscitation strategy and optimizing patient outcomes. The American Heart Association emphasizes that high-quality CPR with minimal interruptions remains the foundation of successful resuscitation regardless of arrest type 2.