Basics of ECG (Electrocardiography)

Introduction

Electrocardiography (ECG or EKG) is a simple, non-invasive test used to assess the electrical activity of the heart. It plays a crucial role in diagnosing various heart conditions, ranging from arrhythmias to heart attacks.

How the ECG Works

The heart generates electrical impulses that coordinate its contractions. Electrodes placed on the skin detect these impulses, and the ECG machine converts them into waveforms displayed on paper or a screen.

Components of an ECG Waveform

  • P wave: Represents atrial depolarization (the electrical activation of the atria).
  • PR interval: Measures the time taken for electrical signals to travel from the atria to the ventricles.
  • QRS complex: Represents ventricular depolarization (the activation of the ventricles that leads to contraction).
  • ST segment: Important for detecting ischemia or infarction.
  • T wave: Represents ventricular repolarization (recovery phase of the ventricles).

Common Clinical Applications of ECG

  • Detecting arrhythmias (abnormal heart rhythms)
  • Identifying myocardial infarction (heart attack)
  • Diagnosing heart chamber enlargement
  • Evaluating signs of electrolyte imbalances
  • Monitoring the effectiveness of cardiac medications

ECG Leads and Placement

A standard ECG consists of 12 leads: - Limb leads (I, II, III, aVR, aVL, aVF): Provide views of the heart in the frontal plane. - Precordial (chest) leads (V1–V6): Offer a horizontal plane view of the heart.

Conclusion

Understanding the basics of ECG is essential for recognizing heart disorders at an early stage. If you experience symptoms like palpitations, chest pain, or dizziness, an ECG helps in timely diagnosis and treatment.

Source recommendations

1. American Heart Association (AHA) Guidelines on Electrocardiography

  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://pubmed.ncbi.nlm.nih.gov/19281932/
  4. https://www.ahajournals.org/doi/10.1161/circulationaha.106.180200
  5. https://cpr.heart.org/en/courses/acls-prep-ecg-pharmacology

2. European Society of Cardiology (ESC) Guidelines on ECG Interpretation

  1. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines
  2. https://academic.oup.com/eurheartj/article-abstract/39/16/1466/2965923
  3. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Neonatal-Electrocardiogram-Guidelines-for-the-interpretation-of-the
  4. https://academic.oup.com/eurheartj/article/39/2/119/4095042
  5. https://www.escardio.org/Guidelines

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