Emergency nurses must rapidly recognize life-threatening cardiac rhythms and initiate appropriate interventions. The Certified Emergency Nurse (CEN®) examination frequently tests rhythm recognition and prioritization of treatment.
While dozens of cardiac rhythms exist, there are several high-yield rhythms that every emergency nurse must identify quickly.
This guide reviews the 10 most important ECG rhythms tested on the CEN exam.
1️⃣ Normal Sinus Rhythm
Rhythm Characteristics
- Heart rate: 60–100 bpm
- Regular rhythm
- Normal P waves present
- Each P wave followed by a QRS complex
- PR interval: 0.12–0.20 seconds
Why It Matters for the CEN Exam
Normal sinus rhythm serves as the baseline for identifying abnormal rhythms.
2️⃣ Sinus Bradycardia
Rhythm Characteristics
- Heart rate less than 60 bpm
- Regular rhythm
- Normal P waves
- Narrow QRS complexes
Common Causes
- Vagal stimulation
- Hypoxia
- Inferior myocardial infarction
- Medication effects (beta blockers)
CEN Exam Insight
Symptomatic bradycardia may require atropine or transcutaneous pacing.
3️⃣ Sinus Tachycardia
Rhythm Characteristics
- Heart rate greater than 100 bpm
- Regular rhythm
- Normal P waves
Common Causes
- Pain
- Hypovolemia
- Fever
- Anxiety
- Hypoxia
CEN Exam Insight
Sinus tachycardia usually indicates an underlying physiological problem.
4️⃣ Atrial Fibrillation
Rhythm Characteristics
- Irregularly irregular rhythm
- No identifiable P waves
- Variable ventricular rate
Clinical Significance
Atrial fibrillation increases the risk of stroke due to clot formation.
CEN Exam Insight
If the patient is unstable, treatment is synchronized cardioversion.
Learn Emergency Medicine From Someone Who Has Lived It
For more than 35 years in emergency medicine, Jeffery Bratcher has worked in environments where seconds matter, prioritization saves lives, and clinical judgment must be immediate.
The CEN® exam tests that exact type of thinking. Elite CEN Prep was built to train emergency nurses to recognize patterns, prioritize care, and answer exam questions the same way experienced ER clinicians think.
This is not memorization. This is clinical reasoning training for emergency nurses.
Train Your Brain to Think Like a Certified Emergency Nurse
The CEN® exam costs nearly $380–$450.
Elite CEN Prep gives you a complete certification system including
2,100+ questions with rationales, 6 full-length exam simulations, and deep-dive training videos.
The full price of Elite CEN Prep will soon increase to $97 as new training modules and content are added.
Secure your access now and lock in the $67 founding price before the increase.
🔥 Start Elite CEN Prep Now ($67)
📚 Purchase the Timed CEN Simulation Exam (150 Questions) $15 Dollars
5️⃣ Supraventricular Tachycardia (SVT)
Rhythm Characteristics
- Heart rate often 150–250 bpm
- Regular rhythm
- P waves often hidden
- Narrow QRS complexes
Clinical Presentation
- Palpitations
- Chest discomfort
- Dizziness
- Shortness of breath
CEN Exam Insight
Stable SVT may be treated with vagal maneuvers or adenosine.
6️⃣ Ventricular Tachycardia (VT)
Rhythm Characteristics
- Heart rate 150–250 bpm
- Wide QRS complexes
- P waves usually absent
Clinical Significance
Ventricular tachycardia can quickly deteriorate into ventricular fibrillation.
CEN Exam Insight
- Stable VT → antiarrhythmic medication
- Unstable VT → synchronized cardioversion
- Pulseless VT → defibrillation
7️⃣ Ventricular Fibrillation
Rhythm Characteristics
- Chaotic waveform
- No identifiable P waves
- No identifiable QRS complexes
Clinical Significance
Ventricular fibrillation results in no cardiac output.
CEN Exam Insight
This rhythm requires immediate defibrillation.
8️⃣ Asystole
Rhythm Characteristics
- Flatline ECG
- No electrical activity
- No cardiac output
Clinical Significance
Asystole represents complete cardiac standstill.
CEN Exam Insight
Asystole is a non-shockable rhythm.
9️⃣ Pulseless Electrical Activity (PEA)
Rhythm Characteristics
- Electrical activity visible on monitor
- No palpable pulse
- No effective cardiac output
Clinical Significance
PEA often results from severe underlying physiological disturbances.
CEN Exam Insight
Treatment focuses on identifying reversible causes known as the H’s and T’s.
🔟 Torsades de Pointes
Rhythm Characteristics
- Polymorphic ventricular tachycardia
- Twisting QRS complexes
- Associated with prolonged QT interval
Common Causes
- Electrolyte abnormalities
- Certain medications
- Congenital long QT syndrome
CEN Exam Insight
The treatment of torsades de pointes is magnesium sulfate.
🧠 Key Rhythm Recognition Concepts for the CEN Exam
- ⚡ Ventricular fibrillation requires immediate defibrillation.
- ⚡ Pulseless ventricular tachycardia is treated the same as ventricular fibrillation.
- 🚫 Asystole and PEA are non-shockable rhythms.
- ❤️ Unstable tachycardias require synchronized cardioversion.
- 💊 Torsades de pointes is treated with magnesium.
⭐ Final Takeaway
Rapid ECG interpretation is a critical skill for emergency nurses and a frequent topic on the CEN exam.
By mastering these 10 essential cardiac rhythms, emergency nurses can recognize life-threatening arrhythmias quickly and initiate lifesaving interventions.
Understanding ECG rhythms improves patient survival and is essential for success on the Certified Emergency Nurse examination.