Understanding Sinus Rhythm on ECG

Introduction

Sinus rhythm is the normal electrical activity of the heart, originating from the sinoatrial (SA) node. Recognizing sinus rhythm on an electrocardiogram (ECG) is crucial as it indicates normal heart function.

Characteristics of Sinus Rhythm on ECG

To determine if an ECG shows a sinus rhythm, it must meet the following criteria:

  • P wave presence: Each QRS complex is preceded by a P wave.
  • Regular rhythm: The RR intervals (time between QRS complexes) are consistent.
  • Heart rate: The normal resting sinus rhythm ranges from 60 to 100 beats per minute (bpm).
  • P wave morphology: The P wave should be upright in leads I, II, and aVF, and inverted in aVR.
  • Constant PR interval: The duration of the PR interval (usually 120–200 ms) remains stable between beats.

Clinical Significance

  • Normal sinus rhythm is a sign of a healthy conduction system.
  • If deviations from sinus rhythm occur, they may indicate arrhythmias such as atrial fibrillation, sinus bradycardia, or tachycardia.
  • Certain medical conditions (e.g., electrolyte imbalances, ischemic heart disease) can disrupt sinus rhythm.

When to See a Doctor

If you experience symptoms such as palpitations, dizziness, fainting, or chest pain, consult a doctor to evaluate your heart rhythm further.

Conclusion

Recognizing sinus rhythm on an ECG helps in assessing heart health. Regular check-ups and ECG monitoring can detect abnormalities early, ensuring timely medical intervention.

Source recommendations

1. American Heart Association ECG Interpretation Guidelines

  1. https://www.heart.org/en/health-topics/heart-attack/diagnosing-a-heart-attack/electrocardiogram-ecg-or-ekg
  2. https://www.ahajournals.org/doi/10.1161/circulationaha.108.191095
  3. https://www.heart.org/-/media/files/affiliates/mwa/kansas-city/kc-cardiac-and-stroke-symposium/2020-event-documents/cardiac-presentations/2-ecg-hockstad.pdf?la=en
  4. https://www.ahajournals.org/doi/10.1161/circulationaha.108.191098
  5. https://pubmed.ncbi.nlm.nih.gov/19281931/

2. European Society of Cardiology Guidelines on Arrhythmias

  1. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Ventricular-Arrhythmias-and-the-Prevention-of-Sudden-Cardiac-Death
  2. https://academic.oup.com/eurheartj/article/43/40/3997/6675633
  3. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Supraventricular-Tachycardia
  4. https://pubmed.ncbi.nlm.nih.gov/36017572/
  5. https://www.ahajournals.org/doi/10.1161/01.cir.0000091380.04100.84

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