Part of the ICU Emergencies Hub — browse every related guide in one place.
Cardiac arrhythmias are abnormalities in the rate, rhythm, or origin of the electrical impulse that initiates each heartbeat. Understanding the EKG basics that underlie arrhythmia recognition, knowing which rhythms are immediately life-threatening, and knowing the nursing response to each is a foundational competency for any nurse working in acute or monitored care.
Every arrhythmia assessment begins with a systematic approach to the rhythm strip. Using the same 5-step framework every time prevents missed findings and builds pattern recognition:
Step 1 — Rate: Calculate the ventricular rate (the number of QRS complexes per minute). Normal: 60–100 bpm. Bradycardia: less than 60. Tachycardia: greater than 100. Methods: count the R-R intervals over 6 seconds and multiply by 10 (for irregular rhythms), or memorize the 300-150-100-75-60-50 rule for regular rhythms (count large boxes between R waves: 1 box = 300, 2 = 150, 3 = 100, 4 = 75, 5 = 60, 6 = 50).
Step 2 — Rhythm: Is the rhythm regular or irregular? Measure R-R intervals across the strip — if the distance between consecutive R peaks is consistent, the rhythm is regular. Variable R-R intervals indicate irregular rhythm. Irregularly irregular (no pattern at all) vs. regularly irregular (a repeating pattern of irregularity) is clinically significant.
Step 3 — P wave: Is there a P wave before every QRS? Is every P wave identical? Does each P wave look normal (upright and rounded in lead II, duration less than 0.12 seconds)? No P waves = atrial fibrillation or junctional rhythm. Abnormal P waves = atrial ectopy. P waves not associated with QRS complexes = heart block.
Step 4 — PR interval: Normal: 0.12–0.20 seconds (3–5 small boxes). Prolonged PR (>0.20 sec) = first degree heart block. Variable PR = second degree heart block. No consistent PR relationship = third degree heart block.
Step 5 — QRS duration: Normal: 0.06–0.12 seconds (less than 3 small boxes). Wide QRS (>0.12 sec) = ventricular origin rhythm, bundle branch block, or aberrant conduction. Narrow QRS = supraventricular origin (above the ventricles).
| Arrhythmia | EKG Finding | Clinical Significance | Nursing Priority |
|---|---|---|---|
| Ventricular Fibrillation (VF) | Chaotic, irregular baseline with no identifiable P waves, QRS, or T waves | Immediately life-threatening; no cardiac output; cardiac arrest | Call code, initiate CPR immediately, prepare for defibrillation — this is a shockable rhythm |
| Pulseless Ventricular Tachycardia (pVT) | Wide, regular QRS complexes at rate 150–250 bpm; no P waves | Immediately life-threatening; no cardiac output despite organized electrical activity; cardiac arrest | Same as VF — call code, CPR, defibrillation; do NOT confuse with stable VT (pulse present) |
| Stable Ventricular Tachycardia | Wide, regular QRS complexes at rate 150–250 bpm; pulse present | Life-threatening; poor cardiac output; may deteriorate to pVT/VF | Immediately notify provider; prepare for cardioversion or antiarrhythmic (amiodarone); monitor closely; do not delay escalation |
| Complete Heart Block (3rd degree AV block) | P waves and QRS complexes independent of each other; very slow ventricular rate (20–40 bpm) | Immediately life-threatening; extremely low cardiac output | Immediately notify provider; may need emergent transcutaneous pacing; atropine rarely effective; prepare for transvenous pacing |
| Atrial Fibrillation (Afib) | Irregularly irregular rhythm; no P waves (fibrillatory baseline); normal QRS width if no aberrancy | Variable — may be well-tolerated or cause hemodynamic compromise; thromboembolic risk if sustained | Assess hemodynamic stability (BP, mental status); new-onset Afib requires immediate provider notification; rate control or rhythm control decision |
| SVT (Supraventricular Tachycardia) | Narrow-complex tachycardia at 150–250 bpm; P waves buried in T waves or absent | Usually not immediately life-threatening; but rapid rate compromises cardiac output if sustained | Assess stability; vagal maneuvers if stable and appropriate; provider notification; prepare adenosine per order |
| Bradycardia with hemodynamic compromise | Rate <50; any rhythm | Life-threatening if patient symptomatic (hypotension, altered mental status, chest pain, syncope) | Immediately notify provider; if symptomatic: atropine 1 mg IV (may repeat); prepare for transcutaneous pacing |
Before escalating for any arrhythmia alarm, the bedside nurse must first assess whether the rhythm on the monitor is real or an artifact. Artifact — electrical interference that mimics rhythm changes — is among the most common causes of code team activation for non-events. The assessment takes 30 seconds and prevents unnecessary alarm escalation:
Go to the patient immediately. Assess: Is the patient conscious and responsive? Are they speaking normally? What is their skin color and diaphoresis status? Feel for a pulse (radial or carotid). If the patient is awake, talking, and has a palpable pulse, the monitor is showing artifact, lead dislodgement, or a benign rhythm — not VF or pVT. A patient in actual VF cannot talk to you. This assessment happens before calling a code.
Check leads: a detached lead electrode, a lead wire caught in the bed rail, or patient movement produces artifact patterns that can appear as fine fibrillation or wide-complex tachycardia. Confirming lead placement before escalating converts many false alarms into rapid fixes.
| Drug | Primary Use | Key Nursing Considerations |
|---|---|---|
| Amiodarone | VF/pVT (code dose), stable VT, Afib rate/rhythm control | Hypotension common with IV infusion; pulmonary, thyroid, hepatic toxicity with long-term use; must use central line or large peripheral IV for high concentration; monitor for QT prolongation |
| Adenosine | Termination of SVT (reentry tachycardias) | Push fast via peripheral IV closest to heart with 20mL saline flush immediately after; patient will experience chest pressure/near-syncope for seconds; very short half-life; asystole is transient and expected at therapeutic dose |
| Atropine | Symptomatic bradycardia | 1 mg IV; may repeat up to 3mg total; ineffective for high-degree AV block (blocks below AV node); paradoxical bradycardia possible with doses below 0.5mg |
| Metoprolol/Labetalol | Rate control in Afib, tachycardia management | Assess BP and pulse before administration; hold for HR <60 or SBP <90 per order parameters; monitor for bronchospasm in patients with reactive airway disease |
| Diltiazem | Rate control in Afib/Aflutter; SVT conversion | IV push may cause hypotension; monitor BP throughout; avoid in decompensated heart failure; do not use in accessory pathway tachycardias (WPW) |
Related guides: ACLS/BLS certification | Cardiac nursing | ICU types comparison | CCRN certification
Get The ICU Notebook Newsletter
Clinical tools and career insights for ICU nurses. One email per week, no fluff.
Yes, send it freeNo spam. Unsubscribe any time.