Determination Of Cardiac Vector Magnitude And Angle In The 4 Quadrant Graph Using Cardiac Vector Theory

INTRODUCTION: The angle determination in ECG is done using the hex-axial reference system with the changes observed in two leads namely Lead I and aVF or using three leads namely Lead I, Lead II and aVF. The angle determination is very difficult in certain conditions. Cardiac vector theory helps in the understanding and determination of cardiac vector magnitude and angle in ECG interpretation. AIM: To derive and calculate the  cardiac vector magnitude and cardiac vector angle and to  correlate with the lead vector in all the 4 quadrants of the hex-axial reference system. MATERIALS AND METHODS: The cardiac vector theory derived using the projection of heart vector onto the lead vector  is applied in detail in different quadrants of the 4 quadrant graph to  derive the  cardiac vector angle and magnitude. RESULTS:The determination of magnitude and angle(axis) of Cardiac vector was  cited with 11 examples. Cardiac vector magnitude and angle determination in each of the 4 quadrant was clearly depicted using graphical figures. CONCLUSION: The cardiac axis calculation  remains an arduous and challenging task. Therefore, this detailed approach using vector principles will serve as an important guide to the medical students to understand and analyze the cardiac axis in various clinical conditions.