Lecture 7 - ECG 1 Flashcards Preview

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Flashcards in Lecture 7 - ECG 1 Deck (17):
1

P wave?

electircal activation of atria

2

QRS wave?

electrical activation of ventricles - muscle activation

3

T wave?

repolarisation of ventricles

4

PR segment?

little to no electrical activity occurring

5

QT segment?

isoelectric period, ventricles polarised

6

Propogating wavefront charges?

resting: inside negative outside positive; active: vice versa - extracellular current flows opposite direction of wavefront movement (positive to negative)

7

Isopotential lines are?

lines of equal potential

8

Vector representation?

direction = direction of dipole (negative to positive), length proportional to strength of dipole

9

Dipole projections?

electrode recording shows the projection on the lead axis, rather than the full dipole

10

Measured dipole depends on?

magnitude of charges (dipole), orientation of dipole and electrodes, distance between dipoles and electrodes

11

Origin of QRS - Q?

top left of IV septum innervated to th right, electrodes record small negative deflection

12

Origin of QRS - R?

progressive innervation to bottom of ventricles, electrodes record big positive charge

13

Origin of QRS - S?

innervation spreads to base of heart, electrodes record slightly bigger negative charge than q

14

Why is T wave positive?

repolarisation changes direction, occuring from epithelium to endothelium due to difference in action potential duration (long on inside), resulting in reversed wavefront movement causing a positive measured dipole

15

Einthoven's triangle?

1 = LA-RA; II=LL-RA, III= LL-LA

16

Unipolar leads?

exploring electrode connected to wilson's central terminal (V=0)

17

Cardiac vector relating to einthoven's triangle?

from centre of triangle to central point of tangents of QRS peaks is the vector - mean QRS axis