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The Normal ECG

In this course, we teach you the basic principles underlying the generation of the 12 lead ECG readout. We explain how the normal depolarization and repolarization events of the cardiac cycle result in a predictable readout recorded by the ECG.

2.0 x AMA PRA Category 1 Credits™
Available on the Pro Plan



In this course, we teach you the basic principles underlying the generation of the 12 lead ECG readout. We teach you the basic vector principles relevant to understanding electrocardiography. We explain how the normal depolarization and repolarization events of the cardiac cycle result in a predictable ECG readout and we detail the terminology used to describe the deflections recorded on the readout. We illustrate the crucial geometrical relationship between the frontal leads of the ECG. We teach you how to measure a range of key variables, the PR interval, the qrs duration, the QT interval and how to calculate the heart rate on the ECG. We explain and describe normal ECG T wave polarity.


Planner and Author: Dr John Seery MB PhD

  • Consultant Physician at St. Vincent's University Hospital, Dublin, Ireland
  • Lecturer at the School of Medicine and Medical Science, University College Dublin, Ireland
  • Studied medicine at the University of Cambridge, United Kingdom
  • A Natural Sciences graduate of Trinity College Dublin, Ireland
  • PhD in Cell Biology from University College London, United Kingdom


Planner: Dr Karen Strahan PhD (University of Cambridge), Head of Editorial
Planner: Tommy O'Sullivan, CME Manager

Estimated Time to Complete

2.0 hours

Target Audience

  • Physicians
  • Nurses
  • Nurse Practitioners
  • Physician Assistants
  • Paramedics

Learning Objectives

Upon successful completion of this activity, you will be able to:

  • Explain the basic principles which allow us to predict  the normal ECG readout
  • Determine the heart rate, the qrs duration, the PR interval and the QT interval from analysis of the ECG
  • Explain the values reported by the computer interpretation on the ECG
  • Identify a normal pattern of T wave polarity on the ECG
  • Identify a normal pattern of qrs morphology on the ECG

Course Content

  • Introduction
  • Cardiac Electrical Activity
  • ECG Generation
  • ECG Nomenclature
  • ECG Lead Perspectives
  • A Short Detour
  • Vectors - General Principles
  • Vectors - Vector Interactions
  • Predicted Normal ECG - Chest Leads
  • Predicted Normal ECG - Frontal Leads
  • Time & the ECG - Part 1
  • Time & the ECG - Part 2
  • Predicted Normal ECG - Refinements
  • Quiz

Release date


Expiration date


Instructions for Participation

Participants must complete the online activity during the valid period as noted above.
Follow these steps:

  1. View videos in sequence
  2. Complete quiz
  3. Complete the activity evaluation form to provide feedback for continuing education purposes and for the development of future activities
  4. Download the Certificate of Completion

Relevant Financial Disclosures

Acadoodle adheres to the ACCME's Standards for Integrity and Independence in Accredited Continuing Education. Any individuals in a position to control the content of a CE activity, including faculty, planners, reviewers or others are required to disclose all relevant financial relationships with ineligible entities (commercial interests). All relevant conflicts of interest have been mitigated prior to the commencement of the activity.

Planners and faculty for this activity have no relevant financial relationships with commercial interests to disclose.


Hampton JR. (1973) The E.C.G. made easy. Churchill Livingston

Garcia T. (2000) 12 Lead ECG: The art of interpretation. Garcia T and Holtz NE Eds. Jones and Bartlett Publishers

Ganong WF. (1983) Review of Medical Physiology. 11th edition. Ed Ganong WF. Lange Medical Publications

Romanes GJ. (1977) Cunningham’s manual of practical anatomy. 14th edition. Oxford University Press

Williams PL. (1980) Gray’s Anatomy. Williams PL, Warwick R. Eds 36th Edition, London, Churchill Livingstone. 

Yanowitz FG. ECG Learning Centre.

Vectors an introduction. Zona Land Education.

Finding the components of a vector. Zona Land Education.

Roche J. Introducing vectors.

Euclidean Vector. Wikepedia

Ashley EA and Niebaur J. Chapter 3 Conquering the ECG (Web based material).

Suzuki J et al. Studies on the positive T wave on ECG in the rat-Based on the analysis for direct cardiac electrocardiograms in the ventricle. Adv Anim Cardiol. 1993;26(1) 24-32.

Hurst JW. Naming the Waves in the ECG, With a Brief Account of Their Genesis. Circulation. 1998;98(18):1937-42.

Susan Boyce Gilmore, Susan L Woods. (1995) Electrocardiography and vectorcardiography. In Cardiac Nursing, 3rd edition. SL Woods, E Sivarajan Froelicher, CJ Halpenny, S Underhill Motzer. JB Lippincott Company.

S.L. Woods, E.S. Sivarajan Froelicher, S. Underhill Motzer, E.J. Bridges. (2005) Cardiac nursing. 5th edition. Lippincott Williams and Wilkins

Goldenberg I et al. QT interval: How to Measure It and What Is Normal. J Cardiovasc Electrophysiol. 2006;17(3):333-6.

Additional Reading

Waller AD. A demonstration on man of electromotive changes accompanying the heart’s beat. J Physiol. 1887;8(5):229-234.

Einthoven W. Die galvanometrische Registrirung des menschlichen Elektrokardiogramms, zugleich eine Beurtheilung der Anwendung des Capillar-Elektrometers in der Physiologie. Pflügers Arch ges Physiol. 1903; 99: 472-480.

Wilson FN et al. Electrocardiograms that represent the potential variations of a single electrode. Am Heart J. 1934;9:447-58.

Barold SS. Willem Einthoven and the Birth of Clinical Electrocardiography a Hundred Years Ago. Card Electrophysiol Rev. 2003;7:99-104.

Fisch C. Centennial of the String Galvanometer and the Electrocardiogram. J Am Coll Cardiol. 2000;36(6):1737-45.

ACCME Accreditation Statement

Acadoodle, Ltd is accredited by the Accreditation Council for Continuing Medical Education (ACCME) to provide continuing medical education for physicians.

Credit Designation Statement

AMA Physician’s Recognition Award

Acadoodle, Ltd designates this enduring material activity for a maximum of 2.0 AMA PRA Category 1 Credits™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.

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