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Electrocardiogram: III

CARDIOVASCULAR PHYSIOLOGY

Norm.il Sequence of Cardiac Depolarization and Repoiarization and Derivation of ECC (continued)

E. Repoiarization

When heart is fully depolarized, there is no electrical acthrity tor brief period (ST segment). Then repoiarization begins from endocardium to epicardium, producing electrical vector directed downward and to leń, causing upward <|»ositive> deflection in both leads I and aVF (T waves). A period of no electrical activity follows, with tracing at baseline until next impulse originates at SA node

	Lead aVF
	K.
	p A T
i
	s

Atrial

depolarization vector

F. Summary of cardiac electrical activity

AV node(pause in conduction)

Late ventricular depolarization vector

Repoiarization

vector

Left and right bundle branches

Septal depolarization vector -

and early left ventricular depolarization vector

Figurę 4.8 Cardiac Depoi arization and Repolarization Part 3-

ECC* continued. Once fully depolarized. electrical activity ceases    generating the T wave of the ECC tracing (panel E). Panel F summa

brietly (the ST segment of the tracing), and then repolarization    rizes the sequence of events in myocardial depolarization and repo-

begins, moving from the inner endocardium to the outer epicardium, larization.

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