1. Electrophysiology Axis Deviation EXSC 531 Clinical Exercise Physiology J. Larry Durstine, PhD Professor and Chair Exercise Science Department School of Public Health University of South Carolina

2. Learning Objective At the end of this lecture, students will be able to understand the concept of axis deviation and determine axis deviation with special considerations.

3. Lecture Outline Determine axis deviation Understand normal physiologic reasons for deviation. Understand pathologic reasons for deviation. Steps for determination Special consideration

4. Axis Deviation Determination If we add up all the small vectors of ventricular depolarization (considering both direction and magnitude), we have one large “Mean QRS Vector” which represents the general direction of ventricular depolarization.

5. Axis Deviation Determination In myocardial infarction there is a necrotic (dead) area of the heart that has lost its blood and does not depolarize. The unopposed vectors from the other side Draw the Mean QRS vector away from the infarct.

6. Axis Deviation Determination Axis is the Mean QRS vector when give in degrees, and the normal axis range is 0 to +90 o in the frontal plane.

7. Axis Deviation Determination In the frontal plane, there are 4 possible axis quadrants where the Mean QRS Vector may point. Visualize this large circle on the patient’s chest in the frontal plane.

8. Now, by looking at the QRS complex in I and AVF, you can locate the Mean QRS Vector in an Axis quadrant (in the frontal plane as it relates to the patient) Determination of Axis Deviation

9. Degrees of Deviation

10. Axis Deviation Determination For this method we will use only the limb and augmented leads Step 1 Determine quadrant – Check leads I and AVF Step 2 Determine the isoelectric lead – Where the QRS has “nearly” equal positive and negative deflections Step 3 Move into the determined quadrant (from step 1) at a 90 degree angle Special consideration –If the isoelectric lead is I, what is the quadrant? –If the isoelectric lead is AVF, what is the quadrant?

11. Determine Quadrant Check leads I and AVF

12. Determine the Isoelectric Lead

13. Move at a Right Angle Move into the determined quadrant (from step 1) at a 90 degree angle

14. Determination of Axis I II III F L R IIIIIIRLF 1.Determine Quadrant. 2.Determine Isoelectric lead. 3.Move at right angle toward quadrant.

15. I II III F L R IIIIIIRLF Determination of Axis 1.Determine Quadrant 2.Determine Isoelectric lead 3.Move at right angle toward quadrant

16. 1. Determine Quadrant 3. Move at right angle toward quadrant I II III F L R IIIIIIRLF Determination of Axis 2. Determine Isoelectric lead

17. I II III F L R IIIIIIRLF Determination of Axis 1.Determine Quadrant 2.Determine Isoelectric lead 3.Move at right angle toward quadrant

18. I II III F L R IIIIIIRLF Determination of Axis 1.Determine Quadrant 2.Determine Isoelectric lead 3.Move at right angle toward quadrant

19. Lecture Outline Determine axis deviation Understand normal physiologic reasons for deviation. Understand pathologic reasons for deviation. Steps for determination Special consideration

20. Lead ILead IIavRavLavFLead III L I II F III R F 2. Determine Isoelectric lead 3. Move at right angle toward quadrant Lead I Lead AVF 1. Determine Quadrant

21. L I II F III R 2. Determine Isoelectric lead 3. Move at right angle toward quadrant Lead ILead IIavRavLavFLead III AVF Lead I G

22. Lecture Outline Determine axis deviation Understand normal physiologic reasons for deviation. Understand pathologic reasons for deviation. Steps for determination Special consideration

24. Determination of Axis Deviation 1.Mean vector 2.Physiologic reasons for deviation 3.Pathogenic reasons for deviation 4.Steps for determination Determine quadrant –Check leads I and AVF Determine the isoelectric lead Move into the determined quadrant at a 90 degree angle 5.Special consideration If the isoelectric lead is I, what is the quadrant? If the isoelectric lead is AVF, what is the quadrant? Counting heart rates 1. R to R Count off Small box counting (1 and 5 contraction methods) 2. Three and six second 3. Know reasons for using each