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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
With transmural ischemia, T waves are ....
Symmetrical Repolarization takes longer but also reverses direction (becomes endocardial-to-epicardial); results in T-wave inversion in leads overlying the ischemic regions
26
T-wave inversion occurs with ischemia because...
Ischemic tissue does not repolarize normally Ischemic T wave is more symmetrical than a normal T wave
27
RAD and asymmetrical T waves are seen in...
RVH with Strain Pattern (another cause of T wave inversion)
28
When might you see peaked (or hyperacute) T waves?
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
29
ST segment depression may or may not include...
T wave inversion
30
How do you determine if ST segment is elevated or depressed?
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
31
Subendocardial ischemia, injury, and infarct involves...
The inner layer of the heart, but does not extend through the entire ventricular wall
32
Progressive subendocardial ischemia and injury may progress to...
A subendocardial myocardial infarction Also called a non-Q wave infarction
33
Flat ST segment depression can result from...
Subendocardial injury or infarction
34
ST segment elevation indicates ....
Myocardial injury, and may indicate that infarction is in progress
35
What is considered significant ST segment elevation?
>1 mm above baseline measured 0.04s to the right of J-point in 2 or more contiguous leads
36
In addition to MIs, ST segment elevation is seen in...
``` Ventricular hypertrophy Conduction abnormalities Pulmonary embolism Spontaneous pneumothorax Intracranial hemorrhage Hyperkalemia Pericarditis ```
37
Diffuse ST segment elevation = ________
Pericarditis, especially if flat or concave, angled back down to the next QRS complex
38
Pathologic Q waves indicate presence of ...
Irreversible myocardial damage or MI
39
Q waves are considered pathologic if...
>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
Why do you see pathologic Q waves with infarctions?
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
Summary of ECG changes in ischemia
* T wave inversion (due to delayed repolarization) * Symmetrical, peaked T waves * ST segment depression
42
Summary of ECG changes in myocardial injury
ST elevation in leads facing injury (due to incomplete depolarization)
43
Summary of ECG changes in infarction
Enlarging or new Q waves due to electrically silent infarcted tissue
44
Necrosis of myocardial cells due to blockage of coronary artery or branch
Myocardial infarction
45
Q wave infarcts are characterized by....
More extensive damage Transmural
46
Non-Q wave infarcts are characterized by....
Less extensive damage Subendocardial
47
Non-Q wave MI’s can be recognized by...
Evolving ST segment and T wave changes without Q waves Evolving ST-T changes may include a variety of patterns
48
Non-Q Wave MI’s are seen in patients with ________ symptoms and elevation in _________
Typical/angina chest pain Myocardial-specific enzymes
49
The right coronary artery perfuses the ....
Right atrium Right ventricle Inferior and posterior walls of the left ventricle
50
The left main coronary artery divides into _______ and ______
Left anterior descending (LAD) branch Left circumflex (LCX) branch
51
The LAD perfuses the....
Anterior and lateral left ventricle Anterior 2/3 of ventricular septum R&L bundle branches
52
The left circumflex artery perfuses the...
Left atrium Anterolateral, posterolateral, and posterior LV
53
Which coronary artery perfuses the: Right atrium
Right coronary artery
54
Which coronary artery perfuses the: Right ventricle
Right coronary artery
55
Which coronary artery perfuses the: Inferior and posterior walls of LV
Right coronary artery
56
Which coronary artery perfuses the: Anterior and lateral left ventricle
LAD
57
Which coronary artery perfuses the: Anterior 2/3 of ventricular septum
LAD
58
Which coronary artery perfuses the: R&L bundle branches
LAD
59
Which coronary artery perfuses the: Left atrium
Left circumflex artery
60
Which coronary artery perfuses the: Anterolateral, posterolateral and posterior LV
Left circumflex artery
61
What type of MI is the patient having: Changes in precordial leads (V1-4) with reciprocal changes in inferior leads
Anterior MI
62
Anterior MI’s are subdivided into...
Septal (V1-V2) Anteroseptal (V1-V3) Anterolateral (V1 or V2 to V5 or V6)
63
What type of MI is the patient having: Changes in Lead I, aVL, V5-6 with reciprocal changes in inferior leads
Lateral MI (aka lateral wall MI)
64
What type of MI is the patient having: Changes in leads II, III, and aVF with reciprocal changes in anterolateral leads
Inferior MI
65
What type of MI is the patient having: Reciprocal changes in V1-2, tall R waves with ST depression in these leads
Posterior MI
66
What is the usual ECG evolution of a Q-wave MI?
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
MI damage is reversible until...
Pathologic Q waves appear
68
Anterior MI’s are characterized by...
Damage to anterior surface of LV ST segment elevation, T wave inversion, and development of pathologic Q waves in leads V1-4
69
An anterior MI is called ______ if V1-3 are involved
Anteroseptal
70
An anterior MI is called _______ if V1 is not involved
Anterior
71
An anterior MI is called _______ if V4-6 is involved
Anterolateral
72
Which leads are over the ventricular septum?
V1, V2, and V3 Ischemic changes in these leads and possibly in the adjacent precordial leads, are often considered to be septal infarctions
73
Ischemic changes in V1 and V2 are considered ...
Septal MI
74
Ischemic changes in V1-3 are considered...
Anteroseptal MI
75
Lateral MIs are characterized by...
ST segment elevation, T wave inversion, and the development of pathologic Q waves in leads I, aVL, V5 and V6
76
Inferior MI’s are characterized by...
ST segment elevation, T wave inversion, and development of pathologic Q waves in leads II, III, and aVf
77
How do you differentiate a new vs an old MI?
Following recovery from an MI, the ST segment is the earliest to normalize, then the T wave, but the Q wave usually persists
78
Classic changes of necrosis (_________), injury (________) and ischemia (__________) may all be seen during the evolution of acute infarctions
Q waves ST elevation T wave inversion
79
Q waves in the absence of ST segment and T wave abnormality generally indicates....
Prior “healed” or “old” infarction
80
How do you recognize posterior MIs?
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
What are the criteria for abnormal R waves (reciprocal changes) seen in Posterior MIs?
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
You should have a high degree of suspicion for a posterior wall MI if....
ST depression in V1-3
83
Where will you see reciprocal ST depression: For Anterior MI (V1-4)
Inferior leads (II, III, aVF)
84
Where will you see reciprocal ST depression: Anteroseptal MI (V1-2)
Inferior leads (II, III, aVF) or lateral leads (I, aVL, V5, V6)
85
Where will you see reciprocal ST depression: Lateral MI (I, aVL, V5-6)
Inferior leads (II, III, aVF) and in some cases leads V1-2
86
Where will you see reciprocal ST depression: Inferior MI (II, III, aVF)
Lead I and aVL (in some cases leads V1-3)

EKG Final (4 decks)

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