EXPORT CITATION

Chapter 3.6 Principles of Electrocardiography

BOOK TITLE: Understanding Medical Physiology: A Textbook for Medical Students

Author
1. Bijlani R.L.
ISBN
9788180612213
DOI
10.5005/jp/books/10999_21
Edition
3/e
Publishing Year
2004
Pages
15
Author Affiliations
1. All India Institute of Medical Sciences, New Delhi
Chapter keywords
haemodynamics, cardiovascular function, physiological variations, exploring electrode, electrical changes, recording system, waveform, resultant vector, cardiac impulse, ventricular depolarization, electrical axis, depolarized area, oscilloscope screen, intrathoracic pressure, atrial extrasystoles, ventricular fibrillation, myocardial ischaemia, ventricular hypertrophy

Abstract

This chapter discusses principles of electrocardiography, which is an important diagnostic and prognostic tool for assessment of cardiovascular function. Electrocardiogram (ECG) measures the potential difference between two points on the body. Flat metallic electrodes are fastened by straps to the appropriate limb. An electrolyte jelly is applied between the electrodes and skin to decrease the skin resistance. The exact waveform of the ECG is the result of an interaction between the electrical changes and the arrangement of electrodes in the recording leads. The observed configuration of the ECG is due to the rapidly changing resultant vector of current flow in the heart during the cardiac cycle. In order to judge whether an ECG is normal, its features in all the thirteen leads should be examined systematically. Ventricular fibrillation may be stopped by applying a defibrillator to the heart. Prolonged hard work by any muscle, including cardiac muscle, leads to adaptive hypertrophy.

© 2019 Jaypee Brothers Medical Publishers (P) LTD.   |   All Rights Reserved