Chart — Cardiac
Rhythm Comparison Chart
A side-by-side comparison of eight major cardiac rhythms — from normal sinus rhythm to ventricular fibrillation — with key ECG characteristics and distinguishing features for rapid identification.
Educational use only. Rhythm identification requires clinical correlation and trained interpretation. Always assess the patient before acting on monitor findings. This material supports nursing education and exam review. It is not medical advice and is not a substitute for clinical judgment, institutional policy, or medical direction. Always follow facility protocols and current provider orders.
How to Use This Chart
Major Cardiac Rhythms
| Rhythm | Rate (bpm) | Regularity | P Waves | PR Interval | QRS |
|---|---|---|---|---|---|
| Normal Sinus Rhythm (NSR) | 60–100 | Regular | Present, upright in II, 1 per QRS | 0.12–0.20 sec | < 0.12 sec (narrow) |
| Sinus Bradycardia | < 60 | Regular | Present, upright in II, 1 per QRS | 0.12–0.20 sec | Narrow |
| Sinus Tachycardia | 100–160 | Regular | Present, may be hidden in T wave at fast rates | Normal | Narrow |
| Atrial Fibrillation | Varies; ventricular 60–160+ | Irregularly irregular | Absent — fibrillatory baseline | Absent | Narrow (usually) |
| Atrial Flutter | Atrial 250–350; ventricular variable | Usually regular (may vary) | Sawtooth flutter waves (F waves) | Variable (flutter:QRS ratio) | Narrow |
| SVT (Supraventricular Tachycardia) | 150–250 | Regular | Often hidden in QRS or T wave; may be retrograde (inverted) | Very short or not measurable | Narrow |
| Ventricular Tachycardia (VT) | 100–250 | Regular | Absent or dissociated (AV dissociation) | Not measurable | ≥ 0.12 sec (wide, bizarre) |
| Ventricular Fibrillation (VF) | Chaotic — no rate | No pattern | Absent | Absent | No identifiable QRS |
Key Distinguishing Features
Normal Sinus Rhythm
The standard against which all other rhythms are compared. Requires: rate 60–100, regular rhythm, P wave before every QRS (upright in lead II), PR 0.12–0.20, QRS < 0.12 sec. All five criteria must be met.
Atrial Fibrillation — The Classic “Irregularly Irregular”
No two consecutive R-R intervals are the same; there is no recognizable pattern to the irregularity. No true P waves — only a wavy fibrillatory baseline. The hallmark is the combination of narrow QRS complexes with completely unpredictable R-R intervals.
Atrial Flutter — Sawtooth Pattern
Classic sawtooth (F-wave) pattern at ~300 bpm atrial rate, best seen in leads II, III, aVF, and V1. Ventricular rate depends on the AV conduction ratio — common ratios are 2:1 (150 bpm ventricular), 3:1 (100 bpm), 4:1 (75 bpm).
SVT — Sudden Onset and Termination
Characterized by abrupt onset and termination (“paroxysmal”). Rate is typically 150–250 bpm. Narrow QRS unless aberrant conduction. P waves are often hidden in or immediately after the QRS. SVT includes AVNRT (most common), AVRT, and atrial tachycardia.
Ventricular Tachycardia — Wide and Fast
Three or more consecutive ventricular ectopic beats at rate > 100 bpm. Wide, bizarre QRS morphology (≥ 0.12 sec). AV dissociation (P waves firing independently of QRS) may be visible. Sustained VT (> 30 sec) with a pulse requires urgent treatment; pulseless VT = cardiac arrest.
Ventricular Fibrillation — Cardiac Arrest
Completely chaotic, disorganized electrical activity. No organized QRS complexes. Coarse VF has larger, more defined waveforms; fine VF resembles a flat line — always check two leads before treating as asystole. Immediate defibrillation is required.
Related Resources
Standards & sources
Fact-checked Jun 20, 2026This page is written to align with AHA / ACC ECG Standards. It is an educational summary, not a citation of any single document — always verify specific doses, values, and protocols against current guidelines and your facility policy. How we source content →