Made available to EKG Club for educational purposes. Slides developed by Hopenfeld.

1. Activation and Repolarization Overview October 2008

2. Heart is an “Electrically” Controlled Pump All normal ECG waveforms result from coordinating the pump coordinating contraction of the pump (QRS complex) coordinating relaxation of the pump (ST segment/T wave/U wave) hold relax contract

3. Contraction Sequence Inside of the heart contracts inwards known as circumferential shortening Diastole End Systole

4. Contraction Sequence And longitudinally Diastole End Systole

5. Contraction Sequence Then, outside of the heart twists/wrings

6. Contraction Sequence In addition to the inside  outside sequence, there is an anterior  posterior sequence apical (bottom)  basal (top) sequence

7. Relaxation Sequence (Mostly) opposite to contraction Outside of the heart untwists associated with rapid suction of blood back into heart Then inside of the heart relaxes Basal (top) to apical (bottom) relaxation However, the anterior  posterior contraction sequence is the same (not opposite) as the relaxation sequence

8. Electrical Sequences Follow (cause!) mechanical sequences Electrical activation (depolarization) of the heart is from the inside out Repolarization of the heart is from the outside in (T wave)

9. Activation In vivo canine heart TOP MID BOT

10. Wigger’s Diagram

11. Heart Cells and Dominoes Dominoes all standing = no current - + V=0

12. Heart Cells and Dominoes They start falling – current flows - + V=5

13. Heart Cells and Dominoes All down – no current flows - + V=0

14. Heart Cells and Dominoes Some start standing – current flows - + V=5

15. Heart Cells and Dominoes Notice that voltage depends on where we measure + - V=-5

16. What about activation potentials? Before wave reaches epi.

17. What about activation potentials? After wave reaches epi. - simulations

18. Activation & Repolarization Comments?