RhythmDockNormal Sinus Rhythm
Find an upright P before every narrow QRS, with a constant PR interval.
ECG RHYTHM LAB
Rhythm reference
23 simplified, generated Lead II examples. Use the monitor to change rate and morphology; use Practice for a short identification exercise.
Sinus Bradycardia
The sinus pattern is preserved; the R–R intervals are longer.
Sinus Tachycardia
Look closely for a consistent P wave before each QRS.
Atrial Fibrillation
No repeating R–R pattern and no consistent P waves.
Atrial Flutter
Look for continuous sawtooth activity, especially between QRS complexes.
Supraventricular Tachycardia
Very regular, rapid narrow complexes with no clearly separate preceding P waves.
Sinus Rhythm with PVCs
Find an early, wide complex with a different shape and a following pause.
Ventricular Tachycardia
A fast, regular rhythm with broad, similar ventricular complexes.
Ventricular Fibrillation
Chaotic changes in amplitude and shape, without identifiable QRS complexes.
Asystole
No identifiable ventricular complexes. A flat trace alone is not a clinical diagnosis.
First-Degree AV Block
Measure the PR: it stays long and every P is followed by a QRS.
Second-Degree AV Block · Mobitz I
Follow successive P waves: longer PR, longer PR, then a missing QRS.
Second-Degree AV Block · Mobitz II
Compare conducted PR intervals: they stay the same around a dropped QRS.
Third-Degree AV Block · Wide Escape
P waves march through the slower ventricular rhythm without a fixed PR.
Junctional Rhythm
A regular narrow rhythm at 40–60 bpm with inverted P waves and a short PR.
Sinus Arrhythmia
Normal P–QRS relationships with repeating, gradual changes in spacing.
Torsades de Pointes · Teaching Pattern
Look for wide complexes that wax, wane and change polarity. Distinguish the pattern from confirmation of torsades, which requires the preceding QT context.
Sinus Rhythm with PACs
Find the early, different P wave before a narrow QRS. The pause is not fully compensatory.
Multifocal Atrial Tachycardia
Identify three P-wave shapes and varying PR intervals, with an isoelectric baseline between P waves.
Wandering Atrial Pacemaker
Changing P-wave shapes and PR intervals distinguish this from sinus arrhythmia.
Atrial Flutter · Variable Conduction
The atrial sawtooth pattern stays organized while R–R intervals change by multiples of the atrial cycle.
Second-Degree AV Block · 2:1
Count two P waves for each QRS; avoid inferring a Mobitz subtype from a 2:1 strip alone.
Third-Degree AV Block · Narrow Escape
P waves march through at their own rate; narrow QRS complexes do not imply normal conduction.