Normal Sinus Rhythm on ECG Library – LITFL Basics

Normal Sinus Rhythm

Tue, 08 Oct 2024 00:00:00 +0000

Overview of normal sinus rhythm (NSR)

The default heart rhythm
Pacemaking impulses arise from the sino-atrial node and are transmitted to the ventricles via the AV-node and His-Purkinje system
This results in a regular, narrow-complex heart rhythm at 60-100 bpm

ECG features of normal sinus rhythm

Regular rhythm at a rate of 60-100 bpm (or age-appropriate rate in children)
Each QRS complex is preceded by a normal P wave
Normal P wave axis: P waves upright in leads I and II, inverted in aVR
The PR interval remains constant
QRS complexes < 100 ms wide (unless co-existent interventricular conduction delay present)

Normal heart rates in children

Newborn: 110 – 150 bpm
2 years: 85 – 125 bpm
4 years: 75 – 115 bpm
6 years+: 60 – 100 bpm

Variations on sinus rhythm

Sinus tachycardia = sinus rhythm with resting heart rate > 100 bpm in adults, or above the normal range for age in children
Sinus bradycardia = sinus rhythm with resting heart rate < 60 bpm in adults, or below the normal range for age in children
Sinus arrhythmia = sinus rhythm with a beat-to-beat variation in the P-P interval (the time between successive P waves), producing an irregular ventricular rate

Example ECG