Understanding ECG Rhythms

Introduction

Electrocardiography (ECG) is a critical tool for assessing the electrical activity of the heart. It helps in diagnosing various heart conditions by analyzing different types of heart rhythms. Understanding ECG rhythms is essential for identifying normal and abnormal heart function.

Types of ECG Rhythms

1. Normal Sinus Rhythm (NSR)

  • Originates from the sinoatrial (SA) node.
  • Regular rhythm with a rate of 60–100 beats per minute (bpm).
  • Consistent P waves before each QRS complex.

2. Sinus Bradycardia

  • Same characteristics as NSR but with a heart rate below 60 bpm.
  • Can be normal in athletes or during sleep but may indicate sinus node dysfunction.

3. Sinus Tachycardia

  • Same characteristics as NSR but with a heart rate above 100 bpm.
  • Can result from stress, fever, anemia, or heart conditions.

4. Atrial Fibrillation (AFib)

  • Irregularly irregular rhythm with absent P waves.
  • Can cause blood clots, increasing the risk of stroke.
  • Often associated with hypertension, heart failure, or valve disease.

5. Atrial Flutter

  • Rapid, regular atrial activity with “sawtooth” P waves.
  • Atrial rate between 250–350 bpm.
  • Can lead to AFib if untreated.

6. Supraventricular Tachycardia (SVT)

  • Narrow QRS complex with rapid heart rate (above 150 bpm).
  • Arises from above the ventricles.
  • Can often be stopped with vagal maneuvers or medications.

7. Ventricular Tachycardia (VT)

  • Regular, fast rhythm originating from the ventricles.
  • Can be life-threatening if sustained.
  • Often linked to ischemic heart disease or electrolyte imbalances.

8. Ventricular Fibrillation (VFib)

  • Chaotic, irregular electrical activity in the ventricles.
  • No effective cardiac output—requires immediate defibrillation.
  • A leading cause of sudden cardiac arrest.

9. Asystole (Flatline)

  • Absence of electrical activity.
  • Requires immediate CPR and advanced cardiac life support interventions.

Conclusion

Recognizing ECG rhythms is crucial for diagnosing cardiac conditions and guiding treatment. While some rhythms are benign, others require urgent intervention to prevent complications, including sudden cardiac death.

Source recommendations

1. American Heart Association (AHA) Guidelines on ECG Interpretation

  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/19281932/

2. European Society of Cardiology (ESC) 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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