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 Normal sinus rhythm strip

ECG features of normal sinus rhythm

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
ECG Normal sinus rhythm

Normal sinus rhythm in a healthy 18-year old male:

  • Regular rhythm at 84 bpm.
  • Normal P wave morphology and axis (upright in I and II, inverted in aVR)
  • Narrow QRS complexes (< 100 ms wide)
  • Each P wave is followed by a QRS complex
  • The PR interval is constant


Advanced Reading

Online

Textbooks


LITFL Further Reading

ECG LIBRARY 700

ECG LIBRARY

Electrocardiogram

Emergency Physician in Prehospital and Retrieval Medicine in Sydney, Australia. He has a passion for ECG interpretation and medical education | ECG Library |

MBBS (UWA) CCPU (RCE, Biliary, DVT, E-FAST, AAA) Emergency Medicine Advanced Trainee in Melbourne, Australia. Special interests in diagnostic and procedural ultrasound, medical education, and ECG interpretation. Editor-in-chief of the LITFL ECG Library. Twitter: @rob_buttner

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