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Flashcards in cardiac conduction 2 Deck (30):
1

P wave =

atrial depolarization

2

QRS =

ventricular repolarization

3

T wave =

T wave =ventricular repolarization

4

PR interval =

index of conduction time across the AV node

5

QT interval =

total duration of depolarization and repolarization

6

The Q is an

initial negative deflection,

7

the R is the

upward deflection

8

the S is a

terminal negative deflection.

9

The sinus node depolarization initiates the

beat but is too small to see
on the ECG.

10

how many separate leads in a ECG?

12

11

the shape of the QRS depends on?

where the positive electrode is placed

12

On EKG, The first signal seen is the

P wave generated by depolarization of first the right and then the left atrium.

13

why is QRS voltage greater than P?

The QRS voltage is much greater than the P voltage because ventricular mass exceeds atrial mass.

14

Why is the T wave wider than QRS?

The T wave is wider than the QRS because ventricular repolarization takes considerably longer than depolarization.

15

why is atrial depolarization not seen?

because normally it s buried in the QRS which is a much larger signal.

16

If the activation wave is _____,
a positive (upward) deflection will be recorded

toward a sensing electrode

17

the ____ the muscle mass, the ___ the voltage recorded

greater
greater

18

the pattern of deflection varies with the____

position of the recording electrodes

19

The SA node is high in the ____ and the depolarization wave sweeps _____.

right atrium

downward and leftward.

20

a lead with a positive electrode near the right arm normally has a predominantly ____ QRS

negative

21

a lead with a positive electrode near the left leg has a ____ QRS.

positive

22

normal sequence of activation of the ventricles

1. The upper portion of the septum is depolarized from left to right.
2. There is then depolarization downward in the septum to the apex.
3. Depolarization is from endocardium to epicardium
4. Depolarization moves upward from apex in the free walls of both ventricles.
5. depolarization of the base of the ventricles.

23

SA (sinoatrial node) abnormalities:

cause “sick sinus syndrome” resulting in slow sinus rates or takeover by other pacemakers which may be either fast or slow.

24

3 types of AV block

1st, 2nd, 3rd degree

25

First degree AV block:

conduction delayed but all P waves conduct to the ventricles.

26

2nd degree block:

some P waves conduct but others do not

27

3rd degree block:

none of the P waves conduct & a ventricular pacemaker takes over

28

When the right bundle is blocked,

QRS widening with delayed conduction to the right ventricle

29

When the left bundle is blocked

QRS widening with delayed conduction to the left ventricle

30

When left bundle fascicles are blocked

there are shifts in direction of depolarization but no QRS widening.