Sudden cardiac arrest is the most critical emergency that can occur to anyone, anywhere, without warning. The key to improving survival and neurological outcomes lies in rapid ECG classification (VF / pulseless VT / PEA / Asystole) and immediate action based on the ICLS (Immediate Cardiac Life Support) protocol.
This comprehensive guide provides frontline healthcare professionals with a clear, structured approach to diagnosing and managing cardiac arrest. Special focus is placed on ECG-based rhythm identification, reversible causes, ICLS-aligned resuscitation flow, and post-ROSC care.
- 📊 Real-world statistics and neurologic outcome scores (CPC)
- 🩺 Shockable vs. non-shockable rhythms and treatment flow
- 🧭 Full ICLS/ALS protocol steps for OSCE and clinical use
- 🌡 Targeted temperature management and prognosis assessment
- 🧒 Considerations for pediatric, pregnant, and trauma cases
- 🎓 How training, simulation, and certifications save lives
Let’s dive into the vital knowledge that can help you act decisively in the first moments of cardiac arrest—and make a difference that lasts a lifetime.
🟨 The Current State of Cardiac Arrest and Why Early Response Matters
📊 A Global Public Health Challenge
Each year, over 350,000 out-of-hospital cardiac arrests (OHCA) occur in the United States alone, with similar incidence rates reported across Europe and other developed nations. Globally, sudden cardiac arrest remains a leading cause of death, with survival to hospital discharge as low as 8–10%.
Most arrests happen at home, often witnessed by family members. Despite advances in resuscitation science, outcomes depend heavily on what happens in the first few minutes after collapse.
🚑 Early Action Saves Lives: Evidence-Based Determinants
Multiple studies have demonstrated that the following factors significantly influence survival and neurological outcomes:
| Key Factor | Impact | Supporting Evidence |
|---|---|---|
| Bystander CPR | 2–3× higher survival rates | Iwami et al., NEJM 2007 |
| Initial shockable rhythm (VF/VT) | 30–50% survival to discharge | Kitamura et al., Circulation 2010 |
| No-flow time | 7–10% drop in survival per minute of delay | Larsen et al., Annals of EM 1993 |
| Early AED use | Significant benefit in VF/VT | Nishiyama et al., Circulation 2015 |
🧠 Neurologic Outcome: CPC Score
The Cerebral Performance Category (CPC) scale is used to assess neurological function after ROSC (Return of Spontaneous Circulation):
| CPC | Description |
|---|---|
| 1 | Good cerebral performance; normal life |
| 2 | Moderate disability but independent in daily life |
| 3 | Severe disability; dependent in daily life |
| 4 | Coma or vegetative state |
| 5 | Death |
🔁 The “Call → Push → Shock” Principle
Three simple actions can dramatically increase the chances of survival:
- Call: Activate emergency services (e.g., 911) immediately.
- Push: Start chest compressions without delay — 100–120/min, at least 2 inches (5 cm) deep.
- Shock: Use an AED as soon as it is available, especially for VF/VT rhythms.
Despite widespread AED availability in many regions, actual bystander CPR rates hover around 40–50%, and AED use remains under 10% in public settings. Ongoing public education is vital to improving these statistics.
🟥 ECG-Based Classification of Cardiac Arrest and the 5H/5T Reversible Causes
📊 Four Rhythms That Define Cardiac Arrest
Once cardiac arrest is identified, the ECG rhythm is the first step in guiding treatment decisions. Cardiac arrest is typically classified into one of four rhythms:
| Rhythm | ECG Characteristics | Shockable? | Main Treatment |
|---|---|---|---|
| Ventricular Fibrillation (VF) | Chaotic, irregular waveform | ✅ Yes | Defibrillation + Epinephrine + Amiodarone |
| Pulseless Ventricular Tachycardia (pVT) | Wide QRS, regular, no pulse | ✅ Yes | Same as VF |
| Pulseless Electrical Activity (PEA) | Organized electrical activity, no pulse | ❌ No | Epinephrine + Search for cause |
| Asystole | Flatline or nearly flat | ❌ No | Epinephrine + Ongoing CPR |
💡 The 5H and 5T Reversible Causes
Reversible causes must always be considered, especially in non-shockable rhythms (PEA and Asystole). The “5H + 5T” mnemonic helps guide systematic assessment:
✅ 5 H’s:
- Hypovolemia – Bleeding, dehydration, or fluid loss
- Hypoxia – Airway obstruction, respiratory failure
- Hydrogen ion (Acidosis) – Metabolic or respiratory acidosis
- Hypo-/Hyperkalemia – Potassium disturbances
- Hypothermia – Core temperature < 30°C
✅ 5 T’s:
- Tension pneumothorax – One-sided breath sounds, tracheal shift
- Cardiac tamponade – Muffled heart sounds, distended neck veins
- Toxins – Drug overdose or poisoning
- Thrombosis (Myocardial infarction) – ST elevation, chest pain history
- Thrombosis (Pulmonary embolism) – Sudden dyspnea, hypotension
📘 COLUMN: ECG Rhythm, Shock, and Prognosis
🔷 Shockable Rhythms (VF/pVT):
These rhythms are usually associated with cardiac causes such as acute myocardial infarction, QT prolongation, or Brugada syndrome. Early defibrillation offers a high chance of survival, with hospital discharge rates as high as 30–50%.
🔷 Non-Shockable Rhythms (PEA/Asystole):
Often linked to non-cardiac causes like hypoxia, trauma, or overdose. Prognosis is poorer (survival rates <10%), and management focuses on identifying and correcting reversible causes.
🔷 Synchronized vs. Unsynchronized Shocks:
| Shock Type | Target Rhythm | When Delivered | Use Case |
|---|---|---|---|
| Synchronized Shock | VT with pulse, Afib, SVT | R-wave timed | For tachycardia |
| Unsynchronized Shock | VF, pulseless VT | Immediate | Cardiac arrest |
Note: AEDs deliver unsynchronized shocks automatically. In manual defibrillation, remember to activate the “sync” mode when needed for tachycardia cases.
🟩 ICLS Protocol: Step-by-Step Guide to Immediate Cardiac Arrest Management
🩺 What is ICLS?
ICLS (Immediate Cardiac Life Support) is a Japanese protocol developed for in-hospital cardiac arrest, aimed at providing high-quality resuscitation with limited resources and personnel. It emphasizes team coordination, rapid rhythm identification, and early intervention based on ECG findings.
🧭 General ALS Workflow (Useful for OSCE and Clinical Practice)
- Check responsiveness, breathing, and pulse simultaneously
- Call for the resuscitation team
- Start chest compressions and attach AED/monitor
- Evaluate rhythm and declare protocol (shockable vs non-shockable)
- Follow shock or non-shock protocol accordingly
- Reassess rhythm and pulse every 2 minutes; give medications and search for reversible causes
- If ROSC is achieved, proceed to post-resuscitation care; if not, continue or terminate CPR based on criteria
📢 Declaring the Protocol: Team Synchronization
Immediately after rhythm assessment, the team leader should announce the protocol to unify team action:
- “VF confirmed — initiating shock protocol.”
- “Asystole — starting non-shock protocol.”
⚡ Shockable Rhythm Protocol (VF / Pulseless VT)
- Deliver one unsynchronized shock
- Immediately resume CPR for 2 minutes
- After 2 minutes, reassess rhythm and pulse + give epinephrine 1 mg IV
- If still in VF/pVT: shock again + CPR
- After third shock, administer amiodarone 300 mg IV
- Optional: additional amiodarone 150 mg IV once
- Continue evaluating and shocking every 2 minutes as appropriate
Note: Epinephrine is repeated every 3–5 minutes during ongoing CPR.
❌ Non-Shockable Rhythm Protocol (PEA / Asystole)
- Start CPR immediately for 2 minutes
- Administer epinephrine 1 mg IV
- Reassess rhythm and pulse
- Search and treat reversible causes (5H/5T)
- Repeat assessment and epinephrine every 2 minutes
Note: Defibrillation and amiodarone are not used in non-shockable rhythms.
🔁 Can the Protocol Be Switched?
Yes, if the rhythm changes during CPR, the protocol must be adjusted accordingly:
- VF → Asystole: switch to non-shock protocol
- PEA → VF: switch to shock protocol and defibrillate
- PEA → ROSC: terminate CPR and initiate post-resuscitation care
🧑🤝🧑 Closed-Loop Team Roles
| Role | Main Tasks |
|---|---|
| Team Leader | Protocol declaration, rhythm decisions, directing team |
| Compressor | Chest compressions, rotate every 2 minutes |
| Airway Manager | Provide ventilation via BVM or intubation |
| IV/Medication | Secure IV line, administer drugs |
| Recorder | Document time, drugs, shocks, ROSC |
All verbal orders must be confirmed and repeated to ensure clarity (closed-loop communication).
🩺 Supplemental Tools and Criteria for Termination
- POCUS: Identify tamponade, PE, cardiac motion
- ABG: Detect acidosis, hyperkalemia, hypoxia
- ETCO₂ < 10 mmHg for sustained period → poor prognosis
- If no ROSC after 20–30 minutes of high-quality CPR + evidence of irreversibility → consider stopping resuscitation
🟦 Post-ROSC Management: Optimizing Outcomes After Return of Spontaneous Circulation
Achieving ROSC (Return of Spontaneous Circulation) is just the beginning. The next hours to days are critical for maximizing neurological recovery, stabilizing vital functions, and preventing recurrence. Here’s a step-by-step guide to post-cardiac arrest care.
🫁 Step 1: Stabilize Airway, Breathing, and Circulation
- Airway: Continue intubation if necessary; secure the airway
- Breathing: Maintain SpO₂ between 94–98%; avoid hyperoxia
- Circulation: Target MAP ≥ 65 mmHg; use vasopressors (e.g., norepinephrine) if needed
- 12-lead ECG: Check for ST-elevation MI → immediate transfer to cath lab if indicated
🧠 Step 2: Neurological Assessment and Monitoring
- Level of consciousness: GCS, pupillary/light reflex
- Imaging: Head CT or EEG to detect cerebral edema, seizures, or bleeding
- Neurological prognosis: Assess using CPC score
CPC 1–2: Favorable neurologic outcome
CPC 3–5: Severe disability or death
🌡 Step 3: Targeted Temperature Management (TTM)
TTM helps reduce the risk of hypoxic brain injury. Guidelines recommend maintaining body temperature between 32–36°C for at least 24 hours.
- Methods: Cooling blankets, catheters, or cold IV fluids
- Cautions: Monitor for arrhythmias, coagulopathy, and infection
- Note: Avoiding hyperthermia is now considered more critical than aggressive hypothermia
🔍 Step 4: Identify Underlying Cause and Prevent Recurrence
- Cardiac causes: ECG, echo, cardiac catheterization
- Non-cardiac causes: PE, hemorrhage, toxins, infection
- Prevention: Treat cause + consider antiarrhythmics, ICD, or lifestyle modifications
📌 Clinical Tips: What to Watch For
- Don’t aim for 100% SpO₂ – hyperoxia is harmful
- Maintain MAP ≥ 65 mmHg but avoid overt vasopressor use
- Start sedation and seizure prevention if needed
- Wait at least 72 hours before final prognosis, unless irreversible signs are evident
🟥 Prognosis and Outcome Evaluation after Cardiac Arrest
Even after successful resuscitation, the chance of meaningful recovery depends largely on neurological function. This section summarizes key predictors and clinical tools for assessing long-term outcomes after cardiac arrest.
📈 Major Prognostic Indicators
| Indicator | Prognostic Impact |
|---|---|
| Initial ECG rhythm (VF/VT) | Best survival rates (30–50%) |
| No-flow time (CPR delay) | 7–10% decrease in survival per minute |
| Low ETCO₂ (<10 mmHg) | Strongly associated with poor outcome |
| Absent pupillary reflex (after 72 hours) | Highly predictive of irreversible brain injury |
| Continuous/reactive EEG | Suggests potential for neurological recovery |
🧠 CPC Score: Cerebral Performance Category
The CPC scale is commonly used to categorize post-arrest neurological function:
| CPC | Condition |
|---|---|
| 1 | Normal brain function; full independence |
| 2 | Mild impairment; independent in daily life |
| 3 | Moderate disability; needs assistance |
| 4 | Coma or vegetative state |
| 5 | Death |
CPC 1–2 is considered a favorable neurological outcome and is often the goal in resuscitation and post-arrest care.
🛑 When to Consider Terminating Resuscitation
If ROSC is not achieved and the following criteria are met, termination of resuscitation may be justified:
- > 20–30 minutes of high-quality CPR with no response
- Persistent ETCO₂ < 10 mmHg
- No cardiac motion on echocardiography
- Fixed, dilated pupils and deep coma
- All reversible causes (5H/5T) ruled out
📘 COLUMN: Communicating a Poor Prognosis
When prognosis is grim, especially after failed resuscitation or severe post-ROSC brain injury, communication with family must balance compassion with medical clarity:
“His heart has restarted, but due to prolonged lack of oxygen, brain recovery is unlikely.”
“Continuing resuscitation would cause more harm than benefit, and unfortunately, the chances of meaningful recovery are extremely low.”
It’s essential to prepare and standardize these conversations within the medical team, always considering the patient’s dignity and family’s emotional state.
🟨 Bystander CPR and Regional Disparities: Empowering the First Responder
📉 The Global Reality of Out-of-Hospital Cardiac Arrest (OHCA)
Unlike in-hospital arrests, OHCA often occurs in private settings—at home, in public, or in transit. Anyone can become the first responder, making public awareness and readiness essential to survival.
Worldwide, OHCA survival to hospital discharge remains low (less than 10%), but that figure rises dramatically when key conditions are met:
- Witnessed collapse
- Immediate bystander CPR
- Initial rhythm is VF/pVT
- Early AED shock delivered
🧍 Importance of Bystander CPR
Studies consistently show that bystander chest compressions can double or triple the chance of survival.
- Global bystander CPR rates: ~40–50%
- Hands-only CPR campaigns have reduced barriers for public participation
⚡ AED Access and Regional Disparities
Automated External Defibrillators (AEDs) are increasingly available, but distribution remains unequal between urban and rural areas:
- Urban: AEDs often reachable within 3 minutes
- Rural: Sparse coverage; AED access may take 10+ minutes
📍 Useful AED Finder Apps (Japan-based examples)
- AED Map (aedm.jp): Crowdsourced; covers over 350,000 units, GPS-enabled
- QQ Map + AED Database: Based on official data; multilingual support
- AED N@VI: Real-time, citizen-powered updates
📞 How to Communicate During Emergency Calls
Using specific words can activate dispatcher-guided CPR and AED support:
- “No breathing”
- “Unconscious”
- “Collapsed and not moving”
These keywords prompt the dispatcher to guide the caller through CPR and provide AED location support. The message is clear: “Call & Push” saves lives.
📘 COLUMN: CPR Education and Community Awareness
Widespread training is key to building a responsive community:
- Mandatory CPR training in middle/high schools
- BLS and AED courses by local fire departments or NGOs
- Community CPR events and AED simulation booths
Healthcare professionals should actively participate in and promote these efforts, bridging the gap between clinical practice and public safety.
🟥 Special Scenarios: Pediatric, Pregnant, and Traumatic Cardiac Arrest
While the basic cardiac arrest algorithm applies to most cases, special populations like children, pregnant women, and trauma patients require tailored approaches. Failure to recognize these differences may lead to suboptimal care.
👶 Pediatric Cardiac Arrest: Often Respiratory in Origin
Up to 80–90% of pediatric cardiac arrests are secondary to respiratory failure or hypoxia. Ventilation plays a much greater role than in adult arrests.
- Common causes: Airway obstruction, severe infection, post-seizure apnea
- Emphasis on ventilation: Prioritize airway and BVM (bag-valve-mask) support
🫀 Chest Compression Techniques:
- 1 rescuer: One-hand chest compressions
- 2 rescuers: Two-thumb encircling hands technique
🫁 Compression-to-Ventilation Ratio:
- 1 rescuer: 30:2
- 2 rescuers: 15:2
Tip: Deliver each breath over 1 second—just enough to make the chest rise visibly.
🤰 Cardiac Arrest in Pregnancy: Two Lives at Risk
In women beyond 20 weeks of gestation, the gravid uterus can compress the inferior vena cava, reducing venous return and the effectiveness of CPR.
Key Modifications:
- Positioning: Left lateral tilt (15–30°) or manual uterine displacement
- Causes: Amniotic fluid embolism, eclampsia, hemorrhage, peripartum cardiomyopathy
- Emergency cesarean delivery: Consider within 4 minutes to improve maternal and fetal survival
In-hospital arrests require coordination with OB, anesthesia, and NICU teams for simultaneous resuscitation and delivery.
🩸 Traumatic Cardiac Arrest: Prioritize the Cause
Most cardiac arrests due to trauma stem from hypovolemic shock or tension physiology, not arrhythmia. Standard CPR may be ineffective unless the cause is addressed first.
Possible Interventions:
- Tension pneumothorax: Immediate needle decompression or chest tube
- Cardiac tamponade: Use POCUS; pericardiocentesis if indicated
- Massive hemorrhage: Rapid hemorrhage control, pelvic binding, IV fluids, and transfusion
Note: In some trauma scenarios, surgical intervention may take priority over prolonged CPR.
📘 COLUMN: DNAR and Ethical Judgments in Special Situations
For patients with advanced disease, dementia, or terminal illness, Do Not Attempt Resuscitation (DNAR) decisions may be ambiguous at the scene. Rapid ethical judgment is sometimes required.
- Default: Start CPR unless there is clear documentation or directive
- Medical criteria: Irreversible signs (e.g., fixed pupils, no cardiac activity, low ETCO₂)
- Communication: Balance clinical explanation with compassion
“We attempted resuscitation, but unfortunately, there were no signs of brain or heart recovery. In light of the situation, we made the decision to stop CPR while preserving dignity.”
🗣️ OET Speaking Section – Useful Phrases During CPR
In emergency scenarios like cardiac arrest, clear and direct communication is critical. Below are standard phrases and useful expressions you may use or hear during CPR in an English-speaking clinical setting—especially relevant for OET Speaking preparation.
🧑⚕️ Common Phrases During Resuscitation
- “Start chest compressions.”
- “Call the resus team.” / “Call a code.”
- “We have no pulse.”
- “Start bag-mask ventilation.”
- “Attach the defibrillator.”
- “Shock delivered. Continue CPR.”
- “Give epinephrine, 1 mg IV.”
- “Reassess rhythm and pulse.”
- “Still in VF, charge the defibrillator.”
- “Switch compressors every two minutes.”
💬 Reassuring Family or Patients (if present)
- “We’re doing everything we can.”
- “We’re trying to restart the heart.”
- “Please wait outside—we’ll update you as soon as possible.”
These expressions can help demonstrate confident, calm, and professional communication under pressure—essential for both clinical work and OET exam scenarios.
🧭 Summary and Take-Home Messages: When Every Second Counts
Cardiac arrest is unpredictable and time-critical. Survival hinges on early recognition, protocol-driven action, and coordinated teamwork. Here’s a recap of key points from this guide.
✅ Key Takeaways
- Start with ECG-based classification: VF / pVT / PEA / Asystole
- Identify shockable rhythms and initiate protocol-based action immediately
- Use the 5H/5T framework to find reversible causes—especially in non-shockable rhythms
- Declare the protocol aloud to synchronize the team
- Post-ROSC care is crucial for neurologic outcomes: oxygenation, perfusion, temperature, cause
- Special considerations apply for pediatric, pregnant, and trauma patients
- Training, simulation, and certification are key to real-life readiness
📢 Final Message
“Resuscitation is a team sport.” – Every role matters: chest compressions, airway management, drug administration, rhythm analysis, and documentation all contribute to saving lives.
“The first 3 minutes matter most” – Help build a community where more people can Call → Push → Shock.
In an age of AI and automation, it’s still your hands and judgment that initiate the chain of survival. Let this guide empower you to act when it matters most.
📚 Related Articles
- ▶ How to Approach Shock: Rapid Diagnosis and Initial Management
- ▶ Assessing Dyspnea: From Asthma and COPD to PE and Heart Failure
- ▶ Syncope vs Seizure: Evaluating Transient Loss of Consciousness
🔗 Read in Japanese
📖 References
- Japanese Society of Emergency Medicine, ICLS Course Manual (5th Ed.)
- JRC Guidelines 2020 (Japanese Resuscitation Council)
- American Heart Association. 2020 AHA Guidelines for CPR and ECC
- Resuscitation Council UK. ALS Provider Manual (2021)
- Global Burden of Cardiac Arrest – WHO & ILCOR Data
- Iwami et al., NEJM 2007; Kitamura et al., Circulation 2010
- Larsen et al., Ann Emerg Med 1993; Nishiyama et al., Circulation 2015
- Japan AED Foundation Survey 2023
- UpToDate: Advanced cardiac life support in adults, 2023