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The Cardiac Axis

The ability to determine the cardiac axis on the ECG is an important clinical skill. In this course, we will explain the meaning of the term cardiac axis. We explain how pathology results in axis deviation on the ECG.

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



The ability to determine the cardiac axis on the ECG is an important clinical skill. In this course, we will explain the meaning of the term cardiac axis. We will teach you a simple method (the hexaxial method) for determining the cardiac axis on the ECG. We will explain how pathology affecting the heart results in axis deviation on the ECG. We define the terms left axis deviation and right axis deviation. We teach you the differential diagnosis of axis deviation detected on the ECG.


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 underlying the determination of the cardiac axis on the ECG
  • Explain the nature of events in the heart resulting in axis deviation on the ECG
  • Determine the cardiac axis on the ECG
  • Identify right or left axis deviation on the ECG
  • Utilize the axes reported by the computer interpretation on the ECG to detect abnormalities relevant to cardiac disease
  • Formulate a differential diagnosis to explain the presence of right axis deviation or left axis deviation on the ECG

Course Content

  • Introduction
  • The Ventricular Conducting System
  • The Cardiac Axis
  • The Cardiac Axis - Deviation
  • Left Axis Deviation - Recognition
  • Right Axis Deviation - Recognition
  • Axis Deviation - Causes
  • The Hexaxial Method
  • P Wave Axis
  • Axes and the Computer Interpretation
  • Quiz
  • Quiz Explanation

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 the quiz
  3. View post quiz video to support learning outcomes and objectives
  4. Complete the activity evaluation form to provide feedback for continuing education purposes and for the development of future activities
  5. 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.


Ferrer MI. The Significance of Axis Deviation. Chest. 1972;61:2-3.

Baltazar RF. (2009) Basic and Bedside Electrocardiography. Lippincott Williams & Wilkins

Finding the components of a vector. Zona Land Education.

Grant RP. Left Axis Deviation. Circulation. 1956;14:233-49.

Surawicz B et al. AHA/ACCF/HRS Recommendations for the Standardization and Interpretation of the Electrocardiogram. Part III. Intraventricular Conduction Disturbances: A Scientific Statement from the American Heart Association Electrocardiography and Arrhythmias Committee, Council on Clinical Cardiology; the American College of Cardiology Foundation; and the Heart Rhythm Society: Endorsed by the International Society for Computerized Electrocardiology. Circulation. 2009;119(10):e235-e240.

Additional Reading

Butterworth JS and Thorpe JJ. On Evaluating the Einthoven Triangle Theory. Circulation. 1951:3:923-5.

Gargiula GD et al. The Einthoven Triangle: A Critical Analysis of the Single Rotating Dipole Hypothesis. Sensors (Basel). 2018;18(7):2353-67.

Benjamin EJ. A Simple device to illustrate an Einthoven triangle. Adv Physiol Educ. 2012;36(4):319-24.

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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