Normal Sinus Rhythm

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 ...