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CVPR Exam I > 6. Cardiac Conduction System & ECG > Flashcards

6. Cardiac Conduction System & ECG Flashcards

1
Q

Cells in the sinoatrial node and AV node are capable of _____.

A

spontaneous depolarization

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2
Q

How are SA and AV node cells able to spontaneously depolarize?

A

their phase 4 periods have slow depolarization due to the funny current and are thereby unstable

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3
Q

What kind of channels are absent in the SA and AV node cells?

A

sodium

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4
Q

Why is the SA node the usual cardiac pacemaker?

A

its cells have the fastest spontaneous depolarization rate, and the AV node cells’ delay allows the atrium to contract first

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5
Q

Why do Purkinje cells have such fast APs?

A

they have a large # of Na channels

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6
Q

What makes up a gap junction?

A

connexins

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7
Q

What is automaticity?

A

the ability to spontaneously depolarize

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8
Q

What is the P wave?

A

depolarization of the R and then L atrium

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9
Q

Where is the AV node located?

A

between the fibrous tricuspid and mitral valve rings that separate the atria from the ventricles

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10
Q

What is found between the fibrous tricuspid and mitral valve rings that separate the atria from the ventricles?

A

the AV node

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11
Q

Where does the depolarization wave go after the AV node?

A

through the bundle of His into the left and right bundle branches

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12
Q

What do the bundle branches divide into?

A

Purkinje fibers

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13
Q

What does the right Purkinje bundle divide into?

A

it doesn’t- it’s a single entity supplying the R ventricle

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14
Q

What does the left Purkinje bundle divide into?

A

anterior and posterior branches or fascicles

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15
Q

What does the QRS complex represent?

A

depolarization of the ventricles

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16
Q

What is the T wave?

A

repolarization of the ventricles

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17
Q

What is phase zero of the ventricular AP?

A

the fast sodium current causes rapid depolarization

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18
Q

What does phase two of the ventricular AP look like?

A

a long plateau and little change in voltage

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19
Q

What does the T wave on the EKG correspond to in the ventricular AP?

A

phase 3- a rapid decrease in voltage as potassium efflux continues

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20
Q

If the _____ is positive the T wave should be positive.

A

QRS

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21
Q

If the QRS is positive the _____ should be positive.

A

T wave

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22
Q

If the QRS is negative the _____ should be negative as well.

A

T wave

23
Q

if the _____ is negative the T wave should be negative as well

A

QRS

24
Q

Discordance between the ___ and ____ in any lead is pathological, reflecting abnormalities such as ischemia or ventricular hypertrophy.

A

QRS and T waves

25
Q

Discordance between the QRS and T waves in any lead is pathological, reflecting abnormalities such as _____ or _____.

A

ischemia; ventricular hypertrophy

26
Q

What is the PR interval?

A

index of conduction time across the AV node

27
Q

What is the index of conduction time across the AV node?

A

the PR interval

28
Q

What is the QT interval?

A

total duration of depolarization and repolarization

29
Q

What is total duration of depolarization and repolarization called?

A

the QT interval

30
Q

How long is a normal P wave?

A

0.08-0.10 s

31
Q

How long is a normal QRS interval?

A

0.08-0.10 s

32
Q

How long is a normal PR interval?

A

0.12-0.2 s

33
Q

How long is a normal Q-Tc interval?

A

less than 0.44 s

34
Q

Where is atrial depolarization in the EKG?

A

it’s buried in the QRS (the larger signal)

35
Q

Where can conduction be delayed or blocked with clinical consequences?

A
  1. SA node block 2. AV node block (3 types) 3. bundle branch blocks (R, L, L bundle fascicles)
36
Q

What does SA node block commonly cause?

A

sick sinus syndrome- slow sinus rates or takeover by other pacemakers

37
Q

What are the 3 types of AV block?

A
  1. first degree- conduction delayed but all P waves conduct 2. 2nd degree- some P waves conduct but others not 3. 3rd degree- none of the P waves conduct and a ventricular pacemaker takes over
38
Q

What is a first degree AV block?

A

conduction delayed but all P waves conduct to the ventricles

39
Q

What is a second degree AV block?

A

some P waves conduct but others do not

40
Q

What is a third degree AV block?

A

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

41
Q

What are the different types of bundle branch blocks?

A
  1. right bundle branch block 2. left bundle branch block 3. left bundle fascicles block
42
Q

What is a right bundle branch block?

A

QRS widening with delayed conduction to the right ventricle

43
Q

What is a left bundle branch block?

A

QRS widening with delayed conduction to the left ventricle

44
Q

What is a left bundle fascicles block?

A

shifts in direction of depolarization but no QRS widening.

45
Q

What are 3 common mechanisms leading to arrhythmia?

A
  1. abnormal re-entry 2. ectopic foci 3. triggered activity
46
Q

Where can abnormal re-entry occur?

A

in the atria, ventricles, or junctional tissue

47
Q

Reentry occurs when there is a _____ and slowed conduction through the reentry pathway.

A

unidirectional block

48
Q

What is the most common cause of serious tachycardias?

A

abnormal re-entry pathways

49
Q

____ occur when a focus of myocardium outside the conduction system acquires automaticity.

A

Ectopic foci

50
Q

Ectopic foci occur when a focus of myocardium outside the conduction system acquires _____.

A

automaticity

51
Q

When does an abnormal rhythm occur?

A

when the rate of depolarization exceeds that of the SA node

52
Q

What is triggered activity?

A

abnormal “afterpolarizations” are triggered by the preceding action potential

53
Q

What are abnormal “afterpolarizations” triggered by the preceding action potential called?

A

triggered activity

54
Q

How does a triggered activity look on an EKG?

A

a long QT interval

CVPR Exam I (29 decks)

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