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Cardiology > ECG Electrophysiology Conduction Pathway > Flashcards

ECG Electrophysiology Conduction Pathway Flashcards

1
Q

Sinoatrial (SA) Node

A

Dominant pacemaker

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2
Q

Sinoatrial (SA) Node location

A

Right atrium, near the inlet of the superior vena cava

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3
Q

Sinoatrial (SA) Node function

A

Receives blood from the right coronary artery

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4
Q

Sinoatrial (SA) Node intrinsic rate

A

Fasted pacemaker in the heart; 60-100 bpm

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5
Q

What is the beating of the heart regulated by?

A

An electrical impulse that causes the characteristic reading of an ECG

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6
Q

Secondary pacemakers

A

If the SA becomes damaged or is suppressed, the farther away from the SA node, the slower its intrinsic rate of firing

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7
Q

Pacemaker rates

A

SA node: 60-100 beats/minute
AV junction: 40-60 beats/minute
Purkinje fibres: 20-40

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8
Q

Atrioventricular (AV) node location

A

Posterior septal wall, right atrium

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9
Q

Atrioventricular (AV) node function

A

Delays impulse conduction, allows time for atria to empty blood into ventricles

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10
Q

Atrioventricular (AV) node intrinsic rate

A

40-60 beats/minute

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11
Q

Bundle branches - ventricles location

A

Interventricular septum

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12
Q

Bundle branches - ventricles function

A

Relays impulse to Purkinje fibres

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13
Q

Bundle branches - ventricles intrinsic rate

A

20-40 beats/minute

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14
Q

Purkinje fibres - ventricles location

A

Ventricular myocardium

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15
Q

Purkinje fibres - ventricles function

A

Relays impulse to myocardium

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16
Q

Purkinje fibres - ventricles intrinsic rate

A

20-40 beats/minute

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17
Q

Dysrhythmias result from?

A

Disorders of impulse formation
Disorders of impulse conduction

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18
Q

Impulse formation

A

Non-pacemaker sites firing

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19
Q

Impulse conduction

A

Blocks, reentry

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20
Q

Enhanced automaticity is an abnormal condition in which one of the following occurs

A

-Cardiac cells that are not normally associated with a pacemaker function begin to depolarize spontaneously
-a pacemaker site other than the SA node increases its firing rate beyond that which is considered normal

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21
Q

What are some causes of enhanced automaticity

A

Ischemia, hypoxia, electrolyte abnormalities, exposure to other chemicals/toxic substances

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22
Q

Abnormal electrical impulses

A

Occur during repolarization (after depolarization) when cells are normally quiet
-requires a stimulus to initiate depolarization

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23
Q

Types of Conduction blocks

A

Partial, complete

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24
Q

Partial conduction block

A

Slowed; all impulses are conducted, takes longer than normal to do so
Intermittent; some impulses are conducted

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25
Q

Complete conduction blocks

A

No impulses are conducted through the affected area

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26
Q

Reentry

A

An impulse returns to stimulate tissue that was previously depolarized

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27
Q

4 lead ECG placement

A

Placed on the limbs / limb leads

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28
Q

12 lead ECG placement

A

Chest and limbs / precordial leads

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29
Q

What is the wave of depolarization moving across the myocardium?

A

Positive

30
Q

Positive deflection

A

Towards positive electrode at left leg results in a positive deflection on the ECG

31
Q

Negative deflection

A

Away from negative electrode at ;eft leg results in a positive deflection on the ECG

32
Q

What does an ECG measure?

A

Electrical events in the heart

33
Q

What is artifact caused by?

A

Muscle tremors, patient movement, loose electrodes / poor contact, pacemaker activity, ambulance moving, 60-cycle interference

34
Q

Lead II

A

Views the inferior surface of the left ventricle

35
Q

One large box (5 squares)

A

5mm or 0.2 seconds

36
Q

One small square

A

1mm or 0.04 seconds

37
Q

Standard recording speed

A

25 mm/sec

38
Q

Vertical axis measures?

A

Voltage/amplitude of the impulse

39
Q

Standard calibration of vertical axis

A

1mm = 0.1 millivolt (mV)
1mV = 10mm or 2 large boxes

40
Q

Horizontal axis = time

A

5 large boxes = 1 second
15 large boxes = 3 seconds
30 large boxes = 6 seconds

41
Q

Baseline

A

Isoelectric line; a straight line recorded when electrical activity is not detected

42
Q

Waveform

A

Movement away from the baseline in either a positive or negative direction

43
Q

Segment

A

A line between waveforms; named by the waveform the precedes or follows it

44
Q

Complex

A

Several waveforms

45
Q

In an isoelectric line, what does ST elevation/depression indicate?

A

A cardiac event; measures deviations above and below isoelectric line

46
Q

P wave

A

First waveform preceding QRS complex, normally upright and rounded in lead II

47
Q

What does a P wave indicate

A

Atrial depolarization

48
Q

Abnormal P waves

A

Notched, peaked, inverted

49
Q

PR interval length

A

0.12 - 0.20 seconds (3-5 small boxes)

> 0.20 means slowed conduction through AV junction

50
Q

What is the PR interval measured from?

A

Start of the P wave to the first deflection or Q wave

51
Q

PR segment

A

Part of PR interval, horizontal line between the end of the P wave and the beginning of the QRS complex

52
Q

Abnormal PR interval - long

A

Greater than 0.20 second; indicates the impulse was delayed as it passed through the atria, AV node or AV bundle

53
Q

Abnormal PR interval - short

A

Less than 0.12 second; may be seen when the impulse originates in the atria close to the AV node or the AV bundle

54
Q

QRS complex

A

Q wave, R wave, S wave, J point

55
Q

Q wave

A

First downward deflection after P wave; often not present

56
Q

R wave

A

First upward deflection after Q or P wave; always positive

57
Q

S wave

A

First downward deflection after R wave; always negative

58
Q

J point

A

Small notch at the start of the ST segment

59
Q

QRS complex length

A

Normally narrow <0.12 sec (3 boxes), measured from beginning of Q or R wave to end of S wave

60
Q

What does QRS complex indicate

A

Ventricular depolarization, atrial repolarization

61
Q

Normal Q wave length

A

Less than 0.3 second

62
Q

Abnormal Q wave length

A

More than 0.3 second in duration or more than 30% of the following R wave height in that lead

63
Q

Normal T waves

A

Slightly asymmetric, usually 0.5 mm or more in height in leads I and II

64
Q

What happens to the T wave following an abnormal QRS complex?

A

Moves in a direction opposite that of the QRS

65
Q

U wave

A

Represent late polarization of Purkinje fibres
Normally small, round, and symmetric
Most easily seen when the heart rate is slow

66
Q

What is ST segment measured from?

A

The end of the QRS complex to the beginning of the T wave

67
Q

What is ST elevation or depression indicative of?

A

Myocardial ischemia or injury

68
Q

What does an ST segment indicate?

A

Early part of repolarization of right and left ventricles

69
Q

Where is the T wave located?

A

First waveform following QRS complex , normally upright and slightly rounded in lead II

70
Q

What does the T wave indicate?

A

Ventricular repolarization

71
Q

QT interval

A

Portion of the ECG tracing from the beginning of the QRS complex to the end of the T wave; represents total ventricular activity

72
Q

R-R interval

A

Used to determine ventricular rate and regularity

Cardiology (12 decks)

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