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Cardiology -ECG > ECG Basics > Flashcards

ECG Basics Flashcards

1
Q

What length of time is 1 small square?

A

0.04 seconds or 40 ms

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2
Q

What length of time is 1 big square?

A

0.2 seconds or 200 ms

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3
Q

What is the standard paper speed?

A

25 mm/sec

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4
Q

What are the possible origins of a narrow complex QRS?

A

Sinus, atrial or junctional origin

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5
Q

What are the possible origins of a wide complex QRS?

A

Ventricular origin or supraventricular with aberrant conduction

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6
Q

Lead I

A

0 degrees (to the left, straight across)

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7
Q

Lead aVF

A

+90 degrees (straight down)

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8
Q

Lead II

A

+60 degrees

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9
Q

Lead III

A

+120 degrees

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10
Q

Lead aVL

A

-30 degrees (towards the left arm)

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11
Q

Lead aVR

A

-150 degrees (to the right arm)

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12
Q

Normal QRS axis?

A

+90 degrees to -30 degrees

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13
Q

Left axis deviation?

A

-30 degrees to -90 degrees

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14
Q

Right axis deviation?

A

+90 degrees to 180 degrees

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15
Q

Extreme/Indeterminate axis deviation?

A

180 degrees to -90 degrees

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16
Q

What is the normal P wave axis range?

A

0 degrees to +75 degrees

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17
Q

Which lead are p waves normally biphasic in?

A

V1

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18
Q

Which lead are P waves usually inverted in?

A

aVR

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19
Q

Which leads are the best to look for atrial abnormalities in?

A

Inferior leads (II, III and aVF) and V1 (P waves are most prominent in these leads)

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20
Q

The first 1/3 of the p wave corresponds to ____ activation, the final 1/3 corresponds to ____ activation; the middle 1/3 is ____

A

Right atrial
Left atrial
A combination of the two

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21
Q

What is the criteria for right atrial enlargement?

A

P wave height > 2.5 mm

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22
Q

What is the criteria for left atrial enlargement?

A

P wave longer than 120 ms (3 small boxes)

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23
Q

What is the criteria for right atrial enlargement in lead V1?

A

Initial positive deflection of p wave > 1.5 mm

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24
Q

What is the criteria for left atrial enlargement in lead V1?

A

Widening (>40 ms) and deepening (>1 mm deep) of terminal negative portion of the P wave

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25
Q

The presence of broad, notched (bifid) P waves in lead II can signify what?

A

Left atrial enlargement (classically due to mitral stenosis)

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26
Q

The presence of tall, peaked P waves in lead II can signify the presence of what?

A

Right atrial enlargement (usually due to pulmonary HTN)

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27
Q

What is a classic sign that there is a non-sinus origin of p waves on an ECG?

A

P-wave inversion in the inferior leads (II, III, aVF)

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28
Q

What is the origin of p waves that are inverted in the inferior leads (II, III, aVF) and PR interval <120?

A

AV junction

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29
Q

What is the origin of p waves that are inverted in the inferior leads (II, III, aVF) and the PR interval is greater than or equal to 120 ms?

A

Origin is within the atria (ectopic atrial rhythm)

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30
Q

What does the presence of multiple p wave morphologies indicate?

A

There are multiple ectopic pacemakers within the atria and/or AV junction

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31
Q

When is multi focal atrial rhythm diagnosed?

A

If 3 or greater P wave morphologies are seen

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32
Q

When is multi focal atrial tachycardia (MAT) diagnosed?

A

If 3 or greater different p wave morphologies are seen and the rate is equal to or greater than 100

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33
Q

What is a Q wave?

A

Any negative deflection that precedes an R wave

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34
Q

Where are small Q waves normally seen?

A

In the left sided-leads: I, aVL, V5 and V6

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35
Q

Which leads are Q waves not normally seen in?

A

Right sided leads (V1-V3)

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36
Q

What are signs of pathological Q waves? (List 4)

A

1) > 40 ms wide (1 small box)
2) > 2 mm deep
3) > 25% of depth of QRS complex
4) Seen in leads V1-V3

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37
Q

Absence of Q waves in leads V5 and V6 are most commonly due to what?

A

Presence of LBBB

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38
Q

List 3 key R wave abnormalities

A

1) Dominant R wave in V1
2) Dominant R wave in aVR
3) Poor R wave progression

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39
Q

What are some possible causes of a dominant R wave in aVR? (List 4)

A

1) Poisoning with sodium-channel blocking agents (e.g. TCAs)
2) Ventricular Tachycardia
3) Dextrocardia
4) Incorrect lead placement (left and right arm leads reversed)

40
Q

T waves are usually upright except in which leads?

A

Leads aVR and V1

41
Q

What are hyperacute T waves? What can they be a sign of?

A

Hyperacute T waves are usually broad or asymmetrically peaked
They can be seen in the early stages of a STEMI (often preceding the appearance of ST elevation and Q waves)

42
Q

What T wave morphology is expected in a bundle branch block? What is this phenomenon called?

A

T wave inversion is usually seen following a QRS pattern suggestive of a bundle branch block or in cases of right/left ventricular hypertrophy
This phenomenon is called “appropriate discordance”, referring to the fact that abnormal depolarization (such as in a bundle branch block) should be followed by abnormal repolarization

43
Q

What are the two main causes of biphasic T waves? How do they differ?

A

1) Myocardia ischemia 2) Hypokalemia
In myocardia ischemia, the T waves go up and then down. In hypokalemia, the T waves go down and then up

44
Q

What is Wellens syndrome? What is it specific for?

A

Wellens syndrome is a pattern of inverted or biphasic T waves in V2-3 in patients presenting with/following ischemic sounding chest pain.
It is highly specific for critical stenosis of the LAD

45
Q

Differentiate Type A and Type B Wellens syndrome

A

Type A: Biphasic T waves (in V2-V3) with the initial deflection positive and the terminal deflection negative
Type B: Deep, inverted T waves (in V2-V3) that are largely symmetric

46
Q

What are two instances that can cause T waves to have a “double peak”?

A

1) Prominent U waves fused to the end of the T wave (as seen in severe hypokalemia)
2) Hidden p waves embedded in the T wave (as seen in sinus tachycardia and various types of heart block)

47
Q

Flattened T waves are non-specific but their presence may represent what? (List 2)

A

1) Ischemia (if dynamic or in contiguous leads)
2) Electrolyte abnormality (e.g. hypokalemia if generalized)

48
Q

Which leads are U waves generally best seen in?

A

Leads V2 and V3

49
Q

When are U waves classified as “prominent”?

A

> 1-2 mm or 25% of the height of the T wave

50
Q

What are 4 drugs or drug classes that can be associated with prominent U waves?

A

1) Digoxin
2) Phenothiazines
3) Class 1a antiarrhythmics (quinidine, procainamide)
4) Class III antiarrhythmics (sotalol, amiodarone)

51
Q

When is U wave inversion abnormal? What is this specific for?

A

U wave inversion is abnormal in leads with upright T waves
Inverted U waves are very specific for myocardia ischemia in patients presenting with chest pain (may be the earliest marker of unstable angina and evolving myocardial infarction)

52
Q

What is a J wave?
List some possible causes (list 3)

A

Small notched wave at the J point
Hypothermia, hypercalcemia, Takotsubo

53
Q

What is an epsilon wave?
Where is it best seen?

A

An epsilon wave is a small deflection buried towards the end of the QRS complex.
It is best seen in the ST segment of V1 and V2; can be present in V1-V4

54
Q

What causes an epsilon wave?

A

Post-excitation of myocytes in the right ventricle

55
Q

What is an epsilon wave a characteristic finding of?

A

An epsilon wave is a characteristic finding in patients with arrhythmogenic right ventricular dysplasia (ARVD)

56
Q

What is the normal PR interval?

A

Between 120-200 ms

57
Q

If the PR interval is > 200 ms, ____ is said to be present

A

First degree heart block

58
Q

PR interval < 120 ms suggests ____ or ____

A

the presence of an accessory pathway between the atria and ventricles
AV nodal (junctional) rhythm

59
Q

Define a junctional rhythm. What are characteristic p wave findings in a junctional rhythm?

A

A junctional, or AV nodal, rhythm is a narrow complex, regular rhythm that arises from the AV node.
P waves are either absent or abnormal (e.g. inverted) with a short PR interval (<120 ms)

60
Q

PR segment elevation or depression can be indicative of what 2 conditions?

A

Pericarditis
Atrial ischemia

61
Q

The QT interval is ______ to heart rate

A

inversely proportional

62
Q

The QT interval ____ at faster heart rates

A

shortens

63
Q

The QT interval ____ at slower heart rates

A

lengthens

64
Q

What is the QTc an estimation of?

A

The corrected QT interval (QTc) is an estimate of the QT interval at a standard heart rate of 60 bpm

65
Q

QTc is prolonged if > ____ in men or > ___ in women

A

> 440 in men
460 in women

66
Q

What are some causes of a prolonged QTc? (List 5)

A

Hypokalemia
Hypomagnesemia
Hypocalcemia
Hypothermia
Medications/Drugs
Myocardial ischemia
Congenital long QT syndrome

67
Q

What are some causes of a short QTc (<350 ms)? List 2

A

Hypercalcemia
Digoxin
Congenital short QT syndrome

68
Q

What are some causes of ST segment elevation? (List 5)

A

Acute myocardial infarction
Coronary vasospasm
Pericarditis
Benign early repolarization
LBBB
LVH
Ventricular aneurysm
Raised intracranial pressure

69
Q

List the septal leads

A

V1-V2

70
Q

List the anteroseptal leads

A

V3-V4

71
Q

List the lateral leads

A

Lead I, aVL, V5-V6

72
Q

List the inferior leads

A

Lead II, III and aVF

73
Q

Name the mnemonic for reciprocal ST changes

A

PAILS

74
Q

Where are the reciprocal changes for a posterior ST elevation?

A

Anterior leads (PAILS)

75
Q

Where are the reciprocal changes for an anterior ST elevation?

A

Inferior leads (PAILS)

76
Q

Where are the reciprocal changes for an inferior ST elevation?

A

Lateral leads (PAILS)

77
Q

Where are the reciprocal changes for a lateral ST elevation?

A

Inferior or Septal lead changes (PAILS) (Only bidirectional letter in mnemonic)

78
Q

Where are the reciprocal changes for a septal ST elevation?

A

Posterior lead changes (PAILS)

79
Q

Acute pericarditis causes widespread concave ST segment elevation with _______ in multiple leads

A

PR segment depression

80
Q

In LBBB, LVH, RBBB and RVH, the ST segments and T waves show _____ because they are directed _____ to the main vector of the QRS complex

A

Appropriate discordance
Perpendicular

81
Q

In LBBB and LVH, RBBB and RVH if a QRS complex has a deep S wave, what are the likely effects on the ST segment and T wave morphology?

A

ST elevation and upright T waves

82
Q

In LBBB, LVH, RBBB and RVH, if a QRS complex has a dominant R wave, what are the likely effects on the ST segment and T wave morphology?

A

ST depression and T wave inversion

83
Q

What is the Brugada sign?

A

ST elevation and partial RBBB in V1-2 with a “coved” morphology

84
Q

Ventricular pacing causes ST segment abnormalities identical to that seen in _____ (______)

A

LBBB
Appropriate discordance

85
Q

Raised intracranial pressure may cause ST segment depression or elevation with _____ T wave ____

A

Deep
Inversion

86
Q

What are some causes of ST depression? (List 5)

A

Myocardial ischemia
Reciprocal change in STEMI
Digoxin effect
Hypokalemia
RBBB
RVH
LBBB
LVH
Ventricularly paced rhythm

87
Q

Horizontal or downsloping ST depression >= ___ mm at the J-point in >= ____ contiguous leads indicates myocardial ischemia

A

0.5 mm
2 contiguous leads

88
Q

Posterior MI manifests as horizontal ST ____ in V1-V3 and is associated with ____ T waves and ____ R waves

A

depression
upright
tall

89
Q

Upsloping ST depression in the precordial leads with prominent De Winter T waves (tall, prominent, symmetrical T waves in the precordial leads) is highly specific for ______

A

Occlusion of the LAD

90
Q

Widespread ST depression with ST elevation in aVR is seen in _____ and _____

A

left main coronary artery occlusion
severe triple vessel disease

91
Q

Supraventricular tachycardia typically causes widespread horizontal ST ____, most prominent in the _____ (___)

A

depression
left precordial leads (V4-V6)

92
Q

In sinus rhythm with frequent ventricular ectopic beats, the narrow beats are ___ in origin and the broad complexes are ____ in origin

A

sinus
ventricular

93
Q

What is the Sokolov-Lyon criteria?
What is it used for?

A

S wave depth in V1 + tallest R wave height in V5-V6 is > 35 mm. This is used to help diagnose LVH

94
Q

The QRS is said to be low voltage when the amplitude of all the QRS complexes in the limb leads are < ___ mm OR the amplitudes of all the QRS complexes in the precordial leads are < ____ mm

A

limb leads -> 5 mm
precordial leads -> 10 mm

95
Q

What is the most important cause for Electrical Alternans?

A

The most important cause is a massive pericardial effusion in which the alternating QRS voltage is due to the heart swinging back and forth within a large fluid-filled pericardium

Cardiology -ECG (1 decks)

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