Contents
A Systematic Approach to Any Rhythm
- 1. Rate: fast (>100), slow (<60), or normal?
- 2. Rhythm: regular or irregular (R-R intervals)?
- 3. P waves: present, uniform, one before each QRS?
- 4. PR interval: normal (0.12–0.20 s) / prolonged / variable?
- 5. QRS: narrow (<0.12 s, supraventricular) or wide (ventricular)?
Sinus Rhythms
- Normal sinus: rate 60–100, regular, upright P before each QRS
- Sinus bradycardia: <60 — treat only if symptomatic (atropine)
- Sinus tachycardia: >100 — treat the CAUSE (pain, fever, hypovolemia, hypoxia)
- Sinus tach is a symptom, not a primary problem — do not just slow the rate
Atrial Fibrillation & Flutter
- AFib: irregularly irregular, no discernible P waves, risk of clot/stroke
- Atrial flutter: sawtooth flutter waves, often regular
- Priorities: rate control (beta-blocker, diltiazem), anticoagulation, rhythm control
- Unstable (hypotension, chest pain, ↓LOC) → synchronized cardioversion
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Start Free Practice →Supraventricular Tachycardia (SVT)
- Narrow-complex, regular, very fast (often 150–250); P waves usually hidden
- Stable: vagal maneuvers first, then adenosine 6 mg rapid IV push (then 12 mg)
- Unstable: synchronized cardioversion
- Warn the patient adenosine causes a brief, frightening pause/flushing
Ventricular Tachycardia (VTach)
- Wide-complex, regular, fast; may be monomorphic or polymorphic (torsades)
- Pulse + stable: amiodarone; prepare for cardioversion
- Pulse + unstable: synchronized cardioversion
- Pulseless VTach: treat like VFib — DEFIBRILLATE (unsynchronized) + CPR
- Torsades: give IV magnesium
Ventricular Fibrillation (VFib)
- Chaotic, no organized QRS, no pulse — immediately lethal
- Shockable: high-quality CPR + DEFIBRILLATION (unsynchronized) ASAP
- Epinephrine every 3–5 min; amiodarone after the first 1–2 shocks
- Minimize interruptions in compressions
Heart Blocks
- 1st degree: PR >0.20 s, constant — usually benign
- 2nd degree Type I (Wenckebach): PR progressively lengthens until a QRS drops
- 2nd degree Type II: constant PR with sudden dropped QRS — can progress to complete block
- 3rd degree (complete): P waves and QRS independent (AV dissociation) — may need pacing
- Symptomatic bradycardia/block: atropine, then transcutaneous pacing
Asystole & PEA (non-shockable)
- Asystole: flat line — confirm in 2 leads; NOT shockable
- PEA: organized rhythm on monitor but NO pulse — NOT shockable
- Treatment: high-quality CPR + epinephrine; find and fix the cause
- Reversible causes: the H's & T's (hypoxia, hypovolemia, H⁺, hypo/hyperkalemia, tension pneumo, tamponade, toxins, thrombosis)
Shockable vs Non-Shockable (ACLS core)
- Shockable: VFib and pulseless VTach → defibrillate
- Non-shockable: asystole and PEA → CPR + epinephrine, no shock
- Synchronized cardioversion is for UNSTABLE patients WITH a pulse (AFib/SVT/VTach with pulse)
- Defibrillation (unsynchronized) is for PULSELESS VFib/VTach
Key ACLS Medications
- Epinephrine: every 3–5 min in all cardiac arrest
- Amiodarone: ventricular arrhythmias (VTach/VFib)
- Adenosine: stable narrow-complex SVT
- Atropine: symptomatic bradycardia
- Magnesium: torsades de pointes
Nursing Priorities
- Always assess the PATIENT, not just the monitor (artifact vs true arrhythmia)
- Check a pulse and level of consciousness to decide stable vs unstable
- Have defibrillator, code cart, and reversible-cause workup ready
- Correct electrolytes (K⁺, Mg²⁺) that provoke arrhythmias
Can you answer these 3 CCRN questions?
Here are 3 questions in the style of our premium bank. The full rationale explains exactly why the right answer is right — and why the distractors trap most test-takers.
Premium Practice Question
A patient is in a narrow-complex, regular tachycardia at 190 with no visible P waves and a stable blood pressure. After vagal maneuvers fail, the nurse anticipates:
- Synchronized cardioversion
- Adenosine 6 mg rapid IV push
- Defibrillation
- Amiodarone 300 mg IV push
Rationale: Stable SVT is treated with vagal maneuvers first, then adenosine 6 mg by rapid IV push; cardioversion is reserved for unstable patients....
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Premium Practice Question
The monitor shows a chaotic waveform with no organized QRS and the patient is pulseless. The priority is:
- Synchronized cardioversion
- Immediate defibrillation and CPR
- Adenosine
- Transcutaneous pacing
Rationale: Pulseless ventricular fibrillation is a shockable rhythm requiring immediate unsynchronized defibrillation and high-quality CPR....
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Premium Practice Question
An EKG shows a progressively lengthening PR interval until a QRS complex is dropped. This is:
- First-degree AV block
- Second-degree AV block Type I (Wenckebach)
- Second-degree AV block Type II
- Third-degree (complete) heart block
Rationale: A progressively lengthening PR interval culminating in a dropped QRS is the hallmark of Wenckebach (Mobitz Type I)....
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Related CCRN Guides
Frequently Asked Questions
How do I systematically read an EKG rhythm?
Work through five steps: rate, rhythm (regular or irregular), P waves (present and uniform?), PR interval, and QRS width. A narrow QRS points to a supraventricular origin and a wide QRS to a ventricular origin.
Which rhythms are shockable?
Only ventricular fibrillation and pulseless ventricular tachycardia are shockable (defibrillation). Asystole and pulseless electrical activity (PEA) are non-shockable and treated with CPR and epinephrine.
What is the difference between defibrillation and synchronized cardioversion?
Defibrillation is an unsynchronized shock for pulseless VFib/VTach. Synchronized cardioversion times the shock to the R wave and is used for unstable patients who still have a pulse, such as unstable AFib, SVT, or VTach with a pulse.
What is the first drug for stable SVT?
After vagal maneuvers, adenosine 6 mg given by rapid IV push (followed by 12 mg if needed) is first-line for stable, narrow-complex SVT.
How is atrial fibrillation managed?
Management focuses on rate control (such as diltiazem or a beta-blocker), anticoagulation to prevent stroke, and rhythm control when appropriate. If the patient is unstable, perform synchronized cardioversion.
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