HYBRID EVENT: You can participate in person at Paris, France or Virtually from your home or work.

3rd Edition of International Heart Congress

June 05-07,2025 | Hybrid Event

June 05 -07, 2025 | Rome, Italy
Heart Congress 2024

Unlocking the cardiac vector theory and einthoven equilateral triangle model: A paradigm shift or a major transition in ECG interpretation?

T Rajini Samuel, Speaker at Cardiovascular Diseases Events
Shri Sathya Sai Medical College and Research Institute, India
Title : Unlocking the cardiac vector theory and einthoven equilateral triangle model: A paradigm shift or a major transition in ECG interpretation?


Introduction: Electrocardiogram (ECG) has offered immense clinical value for more than a century yet its interpretation remains an arduous task and ECG phobia  develops in some of the junior doctors and staff nurses often seeking the help of medical experts in that field. Einthoven used the cardiac vector concept to describe the electrical activity of the heart even before a century but never published a detailed description of it. Many researchers attempted to solve this problem but was not completed. The complete Heart-Lead vector relationship using Cardiac Vector Theory and Einthoven’s equilateral triangle Model was explained in detail by the current author in previous research articles. Cardiac Vector Theory proposed by the current author states that voltage (scalar quantity measured in volt) recorded in a particular lead is the result of dot product between cardiac vector (electrical field vector of dimension volt/metre) and lead vector (measured in metre).

  1. To formulate and apply the cardiac vector Theory in ECG interpretation.
  2. To explain the Einthoven Equilateral Triangle Model for the application of Novel ECG Interpretation

Methods: In the hex-axial reference system of ECG, plot the net voltages of bipolar limb leads and connect them. Similarly, plot the net voltages of unipolar limb leads and connect them. Each forms equilateral triangles. The equilateral triangle can be converted into a circle. Each circles have same origin, same orientation, but different radii because bipolar and unipolar limb leads have different resistance. Multiply each unipolar limb lead voltages by correction factor 1.154 and then plot. Then the  two equilateral triangles are on the same circle.
Results: The voltage recorded by the electrodes (Lead I, II, III, aVR, aVL and aVF) are the vertices of an electrical equilateral triangle. Heart is at the center of the electric field it generates. The right arm, left arm and left leg are the extensions of its electrical field which was compared by Einthoven to a homogeneous volume spherical conductor with heart at the centre of the sphere. Each cardiac wave (P, QRS, T) can be represented in the form of circles. The diameter of the circle denotes the resultant cardiac vector. The perimeter (circumference) of the circle denotes the electrical field of the heart which it generates with heart at the center of the circle. All circles (see the diameter) should be formed in the left lower quadrant except QRS which can go up to -30 degree. When the angle between ‘QRS’ and ‘T’ circles deviate it usually indicates strain, abnormal electrical conduction and  ischemia. The size of a circle will be greater for higher voltage and vice versa. During ST-segment no circle will be formed since it is an iso-electric period. The amount of myocardial injury will be related to the magnitude of circle during the ST-segment.The orientation of the electrode position is represented by the lead vector. The velocity of Cardiac Vector is related with time in the horizontal axis of ECG. The relationship between the magnitude and orientation of heart vector with lead vector produces different voltage deflections in the various leads in the vertical axis. The understanding of the cardiac vector concept helps to clearly analyse and correlate the ECG wave changes in different leads for various cardiac diseases.
Conclusion: The Cardiac Vector Theory and Einthoven’s Equilateral Triangle Model forms the basic foundation in the teaching and understanding of ECG interpretation that helps to overcome the arduous task of pattern memorization method. Coronary artery disease continues to remain as the number one killer disease of the world. So, the combination of the 12-lead ECG with this resultant cardiac vector represented by circle provide the optimum and easier approach to ECG interpretation resulting in saving countless lives of patients. 
Keywords: Cardiac Vector, Lead Vector, Paradigm shift, ECG interpretation

Audience Take Away:

  • Basic Physics involved in ECG
  • Application of  mathematical concepts of scalar and vector.
  • Understanding of Lead Vector Concept and Einthoven’s Equilateral Triangle Model
  • Formulation of Cardiac Vector Theory and its application in ECG Interpretation
  • Novel Approach to Interpret  ECG findings

Cardiac Vector Theory will help in better understanding of ECG that helps in prompt Interpretation of ECG report to  reduce the mortality of the number one killer disease of the


Dr.T.Rajini Samuel is presently working as a Professor of Biochemistry  in Shri Sathya Sai Medical College and Research Institute, Chennai. He did MBBS (2004 -2010) in Chengalpattu Government Medical College, Tamil Nadu, India. He worked in Venkateshwara Hospitals, Chennai to complete the ECG project, proposed cardiac vector theory  and developed a Novel approach using vector concepts to interpret  ECG findings . He completed M.D Biochemistry in Sree Balaji Medical College and Hospitals, Chennai in 2015. He then focused his research on Arterial Blood Gas (ABG) analysis. He  had developed a novel pH based ABG interpretation method, constructed a novel four quadrant graphical tool for ABG interpretation and proposed a novel approach to identify and understand hidden and mixed acid base disorders. He had   derived novel equations of motion in Ventilator Graphics Interpretation for mechanical ventilation. He had published 41 research articles, 3 books and one chapter. He had received High Flyers Global Achievers Award 2022 - The Best Medical Science Researcher,  Atmanirbhar Bharath Award 2022 and Indian Achievers Award 2021 for Excellence in Innovation awarded by the Indian Achievers Forum.