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EKG Final > Myocardial Ischemia and Infarction > Flashcards

Myocardial Ischemia and Infarction Flashcards

1
Q

_______ deliver blood to myocardial cells

_______ return deoxygenated blood to RA via _______

A

Coronary arteries

Coronary veins

Coronary sinus

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2
Q

Coronary blood flow is increased through ________ to meet increased myocardial oxygen demands

A

Vasodilation

Myocardial O2 extraction relatively high at rest (>2/3 max) compared to skeletal muscle (<1/3 max)

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3
Q

What does a normal q wave look like?

A

First negative deflection following PR segment

Amplitude of q wave is <25% of the R wave

Duration <0.04 s (40ms)

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4
Q

Flat line that follows QRS complex

A

ST segment

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5
Q

Where the QRS complex meets the ST segment

A

J point

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6
Q

What does a normal T wave look like?

A

Slightly asymmetrical

Oriented in same direction as preceding QRS complex

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7
Q

What is the maximum height for a normal T wave?

A

5mm in limb leads

10mm in precordial leads

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8
Q

Myocardial ischemia results from…

A

Decreased oxygen and nutrient delivery to the myocardium

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9
Q

Myocardial ischemia can be reversed if…

A

Supply of oxygen and nutrients is restored

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10
Q

Myocardial ischemia can be recognized by…

A

ST segment and T wave changes

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11
Q

Myocardial ischemia generally appears first in the ______ region

A

Sub-endocardial

Deeper myocardial layers are farthest from the blood supply and exposed to greater wall tension

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12
Q

Causes of myocardial ischemia

A

Atherosclerosis

Vasospasm

Thrombosis and embolism

Decreased ventricular filling time (tachycardia)

Decreased filling pressure in coronary arteries (severe HTN or aortic valve disease)

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13
Q

What are the different ischemic sequelae?

A

Non-MI new onset angina (subendocardial ischemia with transient ST depression)

Non-MI variant angina (transmural ischemia with transient ST elevation)

Non-Q MI (NSTEMI) - ST depression or T-wave changes or normal ECG

Q-wave MI (STEMI) - Typical evolution of ST-T changes

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14
Q

In which ischemic sequelae will you see increased troponins?

A

NSTEMI and STEMI

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15
Q

Myocardial injury results if…

A

Ischemia progresses unresolved or untreated

Injury is a greater degree of cell damage than ischemia but w/o actual cell death

ST-T changes

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16
Q

Define myocardial infarction

A

Death of myocardial cells with release of enzymatic break-down products of cell death
• Troponin
• CK-MB
• Myoglobin

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17
Q

What happens if a patient survives their myocardial infarction?

A

The infarcted tissue is replaced with scar tissue

ECG may show Q waves

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18
Q

What are the different degrees of myocardial oxygen deprivation?

A

Ischemia (reversible, no permanent damage)

Injury (prolonged ischemia, onset of cellular damage, but no necrosis)

Infarction (death of injured cells, release of enzymes into circulation)

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19
Q

Depolarization normally proceeds in an ______ to ______ direction

A

Endocardium to epicardial

Conduction system is within in the sub-endocardial tissue

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20
Q

Repolarization usually proceeds from an _____ to _____ direction

A

Epicardial to endocardial

Coronary circulation is on the epicardial surface

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21
Q

General ECG indicators for ischemia

A

Inverted T wave

Tall, peaked symmetrical T wave

Depressed ST segment

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22
Q

General ECG indicators of myocardial injury

A

ST segment changes (ie elevated ST segment)

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23
Q

General ECG indicators of myocardial infarction

A

Q wave changes

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24
Q

What is transmural ischemia?

A

Ischemia involving the entire myocardial wall

More significant, with repolarization taking longer in sub epicardial layers

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25
Q

With transmural ischemia, T waves are ….

A

Symmetrical

Repolarization takes longer but also reverses direction (becomes endocardial-to-epicardial); results in T-wave inversion in leads overlying the ischemic regions

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26
Q

T-wave inversion occurs with ischemia because…

A

Ischemic tissue does not repolarize normally

Ischemic T wave is more symmetrical than a normal T wave

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27
Q

RAD and asymmetrical T waves are seen in…

A

RVH with Strain Pattern (another cause of T wave inversion)

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28
Q

When might you see peaked (or hyperacute) T waves?

A

In early stages of acute myocardial infarction
(>5mm in limb leads or >10mm in precordial leads)

Within a short time during evolution of an acute MI (~2 hours), T waves invert

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29
Q

ST segment depression may or may not include…

A

T wave inversion

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30
Q

How do you determine if ST segment is elevated or depressed?

A

Compare the ST segment to the PR segment

Significant if ST segment is:
• >1mm below baseline measured 0.04s to right of J point
• In 2 or more contiguous leads

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31
Q

Subendocardial ischemia, injury, and infarct involves…

A

The inner layer of the heart, but does not extend through the entire ventricular wall

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32
Q

Progressive subendocardial ischemia and injury may progress to…

A

A subendocardial myocardial infarction

Also called a non-Q wave infarction

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33
Q

Flat ST segment depression can result from…

A

Subendocardial injury or infarction

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34
Q

ST segment elevation indicates ….

A

Myocardial injury, and may indicate that infarction is in progress

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35
Q

What is considered significant ST segment elevation?

A

> 1 mm above baseline measured 0.04s to the right of J-point in 2 or more contiguous leads

36
Q

In addition to MIs, ST segment elevation is seen in…

A 
Ventricular hypertrophy
Conduction abnormalities
Pulmonary embolism
Spontaneous pneumothorax
Intracranial hemorrhage
Hyperkalemia
Pericarditis
37
Q

Diffuse ST segment elevation = ________

A

Pericarditis, especially if flat or concave, angled back down to the next QRS complex

38
Q

Pathologic Q waves indicate presence of …

A

Irreversible myocardial damage or MI

39
Q

Q waves are considered pathologic if…

A

> 0.04s duration
OR
At least 1/3 of the height of R wave in the same QRS complex

AND
Present in 2 or more contiguous leads

40
Q

Why do you see pathologic Q waves with infarctions?

A

Infarcted areas of heart fail to depolarize (become electrically silent) as they are functionally dead

May take hours or days to develop

May persist for life

41
Q

Summary of ECG changes in ischemia

A
  • T wave inversion (due to delayed repolarization)
  • Symmetrical, peaked T waves
  • ST segment depression
42
Q

Summary of ECG changes in myocardial injury

A

ST elevation in leads facing injury (due to incomplete depolarization)

43
Q

Summary of ECG changes in infarction

A

Enlarging or new Q waves due to electrically silent infarcted tissue

44
Q

Necrosis of myocardial cells due to blockage of coronary artery or branch

A

Myocardial infarction

45
Q

Q wave infarcts are characterized by….

A

More extensive damage

Transmural

46
Q

Non-Q wave infarcts are characterized by….

A

Less extensive damage

Subendocardial

47
Q

Non-Q wave MI’s can be recognized by…

A

Evolving ST segment and T wave changes without Q waves

Evolving ST-T changes may include a variety of patterns

48
Q

Non-Q Wave MI’s are seen in patients with ________ symptoms and elevation in _________

A

Typical/angina chest pain

Myocardial-specific enzymes

49
Q

The right coronary artery perfuses the ….

A

Right atrium

Right ventricle

Inferior and posterior walls of the left ventricle

50
Q

The left main coronary artery divides into _______ and ______

A

Left anterior descending (LAD) branch

Left circumflex (LCX) branch

51
Q

The LAD perfuses the….

A

Anterior and lateral left ventricle

Anterior 2/3 of ventricular septum

R&L bundle branches

52
Q

The left circumflex artery perfuses the…

A

Left atrium

Anterolateral, posterolateral, and posterior LV

53
Q

Which coronary artery perfuses the:

Right atrium

A

Right coronary artery

54
Q

Which coronary artery perfuses the:

Right ventricle

A

Right coronary artery

55
Q

Which coronary artery perfuses the:

Inferior and posterior walls of LV

A

Right coronary artery

56
Q

Which coronary artery perfuses the:

Anterior and lateral left ventricle

57
Q

Which coronary artery perfuses the:

Anterior 2/3 of ventricular septum

58
Q

Which coronary artery perfuses the:

R&L bundle branches

59
Q

Which coronary artery perfuses the:

Left atrium

A

Left circumflex artery

60
Q

Which coronary artery perfuses the:

Anterolateral, posterolateral and posterior LV

A

Left circumflex artery

61
Q

What type of MI is the patient having:

Changes in precordial leads (V1-4) with reciprocal changes in inferior leads

A

Anterior MI

62
Q

Anterior MI’s are subdivided into…

A

Septal (V1-V2)

Anteroseptal (V1-V3)

Anterolateral (V1 or V2 to V5 or V6)

63
Q

What type of MI is the patient having:

Changes in Lead I, aVL, V5-6 with reciprocal changes in inferior leads

A

Lateral MI (aka lateral wall MI)

64
Q

What type of MI is the patient having:

Changes in leads II, III, and aVF with reciprocal changes in anterolateral leads

A

Inferior MI

65
Q

What type of MI is the patient having:

Reciprocal changes in V1-2, tall R waves with ST depression in these leads

A

Posterior MI

66
Q

What is the usual ECG evolution of a Q-wave MI?

A
  1. Normal ECG
  2. Hyperacute T wave changes w/ ST elevation
  3. Marked ST elevation w/ hyperacute T wave changes
  4. Pathologic Q waves, less ST elevation, terminal T wave inversion
  5. Pathologic Q waves, T wave inversion
  6. Pathologic Q waves, upright T waves
67
Q

MI damage is reversible until…

A

Pathologic Q waves appear

68
Q

Anterior MI’s are characterized by…

A

Damage to anterior surface of LV

ST segment elevation, T wave inversion, and development of pathologic Q waves in leads V1-4

69
Q

An anterior MI is called ______ if V1-3 are involved

A

Anteroseptal

70
Q

An anterior MI is called _______ if V1 is not involved

71
Q

An anterior MI is called _______ if V4-6 is involved

A

Anterolateral

72
Q

Which leads are over the ventricular septum?

A

V1, V2, and V3

Ischemic changes in these leads and possibly in the adjacent precordial leads, are often considered to be septal infarctions

73
Q

Ischemic changes in V1 and V2 are considered …

74
Q

Ischemic changes in V1-3 are considered…

A

Anteroseptal MI

75
Q

Lateral MIs are characterized by…

A

ST segment elevation, T wave inversion, and the development of pathologic Q waves in leads I, aVL, V5 and V6

76
Q

Inferior MI’s are characterized by…

A

ST segment elevation, T wave inversion, and development of pathologic Q waves in leads II, III, and aVf

77
Q

How do you differentiate a new vs an old MI?

A

Following recovery from an MI, the ST segment is the earliest to normalize, then the T wave, but the Q wave usually persists

78
Q

Classic changes of necrosis (_________), injury (________) and ischemia (__________) may all be seen during the evolution of acute infarctions

A

Q waves

ST elevation

T wave inversion

79
Q

Q waves in the absence of ST segment and T wave abnormality generally indicates….

A

Prior “healed” or “old” infarction

80
Q

How do you recognize posterior MIs?

A

Lack of ECG leads there, so you look for reciprocal changes in leads V1 and V2

Look for abnormal R waves in V1 and V2 with ST depression

81
Q

What are the criteria for abnormal R waves (reciprocal changes) seen in Posterior MIs?

A

R waves in V1/V2 that are:
• ≥ 0.04s in duration
• R≥S
• Patient >30 yo

No signs of RVH

Sometimes see Q waves in V6 too

82
Q

You should have a high degree of suspicion for a posterior wall MI if….

A

ST depression in V1-3

83
Q

Where will you see reciprocal ST depression:

For Anterior MI (V1-4)

A

Inferior leads (II, III, aVF)

84
Q

Where will you see reciprocal ST depression:

Anteroseptal MI (V1-2)

A

Inferior leads (II, III, aVF) or lateral leads (I, aVL, V5, V6)

85
Q

Where will you see reciprocal ST depression:

Lateral MI (I, aVL, V5-6)

A

Inferior leads (II, III, aVF) and in some cases leads V1-2

86
Q

Where will you see reciprocal ST depression:

Inferior MI (II, III, aVF)

A

Lead I and aVL (in some cases leads V1-3)

EKG Final (4 decks)

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