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CVPR > CV - electrocardiogram > Flashcards

CV - electrocardiogram Flashcards

1
Q

the ___________ node is the typical cardiac pacemaker.

A

SA

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2
Q

the SA node is the typical cardiac pacemaker because it has the ___________ spontaneous rate.

A

fastest

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3
Q

the AV node has a slower spontaneous rate and delays conduction at the junction between the ___________ and ___________.

A

atria

ventricles

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4
Q

purkinje cells conduct faster than ___________ cells.

A

contractile myocytes

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5
Q

parking cells allow extremely rapid conduction from the AV node to the ventricles through the ___________ and their extensions into the myocardium.

A

left and right bundles

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6
Q

what does the P wave of an ECG represent?

A

depolarization of the atria

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7
Q

what does the QRS of an ECG represent?

A

depolarization in the ventricles

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8
Q

what does the T wave of an ECG represent?

A

repolarization of the ventricles

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9
Q

is repolarization of the atria appreciated on an ECG?

A

no, repolarization of the atria is not seen because it normally occurs at the same time as ventricular depolarization and is buried in the much larger QRS signal from the ventricles

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10
Q

if the QRS is positive, the T wave should be ___________.

A

positive

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11
Q

if the QRS is negative, the T wave should be ___________.

A

negative

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12
Q

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

A

ischemia

ventricular hypertrophy

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13
Q

the endocardium depolarizes ___________ the epicardium.

A

before

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14
Q

epicardial cells repolarize ___________ endocardial cells.

A

before

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15
Q

epicardial cells repolarize before endocardial cells because they have shorter ___________.

A

action potential duration

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16
Q

the first signal on the ECG is the ___________.

A

P wave

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17
Q

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

A

depolarization

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18
Q

describe the Q of the QRS wave on an ECG.

A

an initial negative deflection during ventricular depolarization

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19
Q

describe the R of the QRS wave on an ECG.

A

the upward deflection

20
Q

describe the S of the QRS wave on an ECG.

A

a terminal negative deflection

21
Q

if the activation wave is toward the sensing electrode, a ___________ deflection will be recorded.

A

positive (upward)

22
Q

the greater the muscle mass the ___________ the voltage recorded.

A

greater

23
Q

the pattern of the deflection varies with the ___________ of the recording electrodes.

A

position

24
Q

the SA node is located high in the ___________ and the depolarization wave sweeps ___________ and ___________.

A

right atrium
downward
leftward

25
Q

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

A

negative

26
Q

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

A

positive

27
Q

the upper portion of the septum is depolarized from ___________ to ___________.

A

left to right

28
Q

what are the sites at which conduction can be delayed or blocked with clinical consequences? (6)

A 
sinoatrial (SA) node
atrioventricular (AV) node
right bundle branch
left bundle branch
posterior fascicular branch
anterior fascicular branch
29
Q

SA node abnormalities commonly cause ___________, resulting in ___________ or ___________.

A

“sick sinus syndrome”
slow sinus rates
takeover by other pacemakers which may be either faster or slower

30
Q

3 types of AV block

A

first degree: conduction is delayed but all P waves conduct to the ventricles
second degree: some P waves conduct but others do not
third degree: none of the P waves conduct and a ventricular pacemaker takes over

31
Q

how does a right bundle branch block appear on ECG?

A

QRS widening with delayed conduction to the right ventricle

32
Q

how does a left bundle branch block appear on ECG?

A

QRS widening with delayed conduction to the left ventricle

33
Q

how does a fascicle block appear on ECG?

A

shifts in direction of depolarization but no QRS widening

34
Q

what is the normal sequence of activation of the ventricles?

A

1 upper portion of the septum is depolarized from left to right
2 there is then depolarization downward int he septum to the apex
3 depolarization is from endocardium to epicardium
4 depolarization moves upward from the apex in the free walls of both ventricles
5 finally there is depolarization of the base of the ventricles

35
Q

what are the common mechanisms leading to arrhythmia?

A

reentry
ectopic foci
triggered activity

36
Q

describe abnormal reentry

A

abnormal reentry pathways can be present in the atria, ventricles or the junctional tissues, and occurs when there is a unidirectional block and slowed conduction through the reentry pathway

reentry is the most common mechanism of serious tachycardias

37
Q

describe ectopic foci

A

ectopic foci occur when a focus of myocardium outside the conduction system acquires automaticity; if the rate of depolarization exceeds that of the SA node, an abnormal rhythm occurs

ectopic foci result in isolated “ectopic beats” or sustained tachyarrhythmias

38
Q

describe triggered activity

A

abnormal “afterpolarizations” may be triggered by the preceding action potential; delayed afterpolarizations appearing after an action potential is complete can trigger arrhythmias, and afterpolarizations when action potentials have only partially depolarized triggers a tachyarrhythmia

arrhythmias due to this mechanism are usually associated with a delay in repolarization seen in the ECG as a “long QT interval”

39
Q

what induces the depolarization in phase 0 of the slow cardiac action potential?

A

calcium current

40
Q

why do contractile myocytes display a more rapid depolarization during phase 0 of the fast cardiac action potential?

A

sodium current

41
Q

why do purkinje cells conduct faster than contractile myocytes?

A

they have more fast Na+ channels

42
Q

what phase of the action potential does the initial R spike on an ECG correspond to?

A

phase 0

43
Q

what phase of the action potential does the ST segment on an ECG correspond to?

A

phase 2

44
Q

what phase of the action potential does the T wave on an ECG correspond to?

A

phase 3

45
Q

what phase of the action potential does the plateau following the T wave on an ECG correspond to?

A

phase 4

CVPR (14 decks)

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