ECG Deflections and Waveforms

Raja Selvaraj MD DNB FCE (Toronto)
Cardiac Electrophysiologist
Professor of Cardiology
JIPMER

Introduction

The heart is a two chambered organ

heart.jpg

Anatomy of a wave

ECG deflection and wavefront

depolarisation_wave.png

Limb leads

limb_leads.png

Wavefronts in atrium

atrium_activation.jpg

Wavefronts in ventricle

ventricle_activation.jpg

P wave

Atrial vectors

atrial_vectors.png

P wave - two atria

p_wave_parts.png

P wave lead II

leadII.png

P wave lead V1

leadv1.png

Other P waves

abnormal_p_wave.jpg

Ta wave

ta_wave.png

QRS and T waves

QRS - Terminology

qrs_terminology.png

Ventricular activation

ventricular_activation.png

Septal q

septal_q.png

Ventricular activation

qrs_vector.png

Bundle branch blocks

bbb.jpg

T wave

t_wave.png

Summary

What have we learnt ?

  • Electrical activation occurs as waves of depoalrisation and repolarisation
  • Wavefronts moving towards or away from recording electrode produce a deflection in the ECG
  • Deflections produced by the atrium and ventricle can be used to infer the activation patterns
  • Forms the basis for all further discussion on the ECG