Understanding ECG (Electrocardiogram)

Introduction

An electrocardiogram (ECG or EKG) is a test that records the electrical activity of the heart over a period of time. It helps diagnose various heart conditions and assess overall cardiac health.

Basic Principles of ECG

The heart generates electrical impulses that regulate its contraction and relaxation. These impulses are detected by electrodes placed on the skin and recorded as waves on an ECG.

Components of an ECG

  1. P wave: Represents atrial depolarization (contraction of the atria).
  2. QRS complex: Represents ventricular depolarization (contraction of the ventricles). It consists of:
    • Q wave (small downward movement)
    • R wave (sharp upward movement)
    • S wave (downward movement after R)
  3. T wave: Represents ventricular repolarization (relaxation of the ventricles).
  4. PR interval: The time between the start of atrial contraction and the start of ventricular contraction.
  5. QT interval: The time it takes for the ventricles to depolarize and repolarize.

Normal vs Abnormal ECG

  • Normal ECG: Regular rhythm, consistent waveform patterns, and normal intervals.
  • Abnormal ECG: Irregular rhythms (arrhythmias), abnormal waveforms (ischemia, infarction), or prolonged intervals (QT prolongation).

Common Conditions Diagnosed with ECG

  • Arrhythmias (Atrial fibrillation, ventricular tachycardia)
  • Myocardial infarction (Heart attack)
  • Ischemia (Reduced blood flow to the heart)
  • Hypertrophy (Enlargement of the heart chambers)

Conclusion

ECG is a fundamental tool in cardiology used for diagnosing and monitoring heart diseases. Understanding its basic components helps in recognizing normal and abnormal heart activity.

Source recommendations

1. American Heart Association 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/19281931/

2. European Society of Cardiology Guidelines on ECG Interpretation

  1. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines
  2. https://pubmed.ncbi.nlm.nih.gov/12269267/
  3. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Neonatal-Electrocardiogram-Guidelines-for-the-interpretation-of-the
  4. https://academic.oup.com/eurheartj/article-abstract/39/16/1466/2965923
  5. https://www.jacc.org/doi/10.1016/j.jacc.2017.01.015

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