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EKG > Lecture 7 > Flashcards

Lecture 7 Flashcards

1
Q

______ deliver blood to myocardial cells

A

Coronary Arteries

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2
Q

______ return deoxygenated blood to RA via coronary sinus

A

Coronary Veins

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3
Q

Q wave

A
  • First part of QRS
  • First downward deflection from baseline
  • Amp of Q wave is less than 25% of the R wave
  • Duration
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4
Q

ST segment

A
  • Flat line that follows the QRS complex and connects it to T wave
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5
Q

T wave

A
  • Slightly asym and oriented in same direction as preceding QRS complex
  • Max ht 5mm in limb leads; 10mm in precordial leads
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6
Q

Myocardial ischemia

A
  • Can be reversed if supply of oxygen and nutrients is restored
  • T wave and ST segment changes
  • NO permanent damage
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7
Q

Where are the coronary arteries?

A

Epicardial surface of the heart

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8
Q

Where does myocardial ischemia generally appear first?

A

Sub-endocardial region

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9
Q

Causes of Myocardial Ischemia

A
  • Atherosclerosis
  • Vasospasm
  • Thrombosis/embolism
  • Decreased ventricular filling time (tachycardia)
  • Decreased filling pressure in coronary arteries (severe hypotension or aortic valve dz)
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10
Q

Examples findings that are Not MIs (6)

A
  • Subendocardial ischemia
  • Transient ST depression
  • New onset angina
  • Transmural ischemia
  • Transient ST elevation
  • Variant angina
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11
Q

No Q MI (2)

A
  • Non-ST elevation MI

- ST depression or T wave changes or normal ECG

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12
Q

Q wave MI (2)

A
  • ST elevation MI

- Typical evolution of ST-T changes

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13
Q

Myocardial injury

A
  • Occurs if ischemia progresses unresolved or untreated
  • INJURY is a great degree of cell damage than ischemia, but without actual cell death
  • ST changes
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14
Q

Mycardial infarction

A
  • Death of myocardial cells
  • Release of enzymatic breakdown products (Troponin, CK-MB, Myoglobin)
  • If the pt survives, the infarcted tissue is replaced with scar tissue (EKG may show Q waves)
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15
Q

Direction of Depolarization

A
  • Normally proceeds in an endocardial to epicardial direction
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16
Q

Where is the conduction system?

A

Subendocardial tissue

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17
Q

Direction of Repolarization

A
  • Repolarization usually proceeds from an epicardial to endocardial direction
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18
Q

Where is the coronary circulation system?

A

Epicardial surface

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19
Q

Characteristics of Myocardial Ischemia

A
  • Inverted T waves
  • Tall, peaked T wave
  • Depressed ST segement
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20
Q

Transmural Ischemia

A
  • More significant ischemia involving the full myocardial wall, from endo to epicardium
  • Repolarization reverses direction (endo to epicardial)
  • T wave inversion in leads in ischemic regions
  • T WAVES ARE SYMMETRICAL
21
Q

T wave inversion

A
  • Occurs because ischemic tissue DOES NOT REPOLARIZE NORMALLY
  • Ischemic T wave is more SYMMETRICAL than a normal T wave (rt and lt sides are mirror images)
22
Q

Peaked T waves (when is it seen, where is it seen)

A
  • May be seen in early stages of acute MI
  • > 6mm in limb leads
  • > 12 mm in precord
23
Q

ST Segment depression

A
  • Significant ST segment > 1 mm below baseline measured 0.04 s to right of J pt, in 2 or more leads
24
Q

Subendocardial Ischemia

A
  • Inner layer of the heart and does not extend through entire ventricular wall
25
Q

What is the last place to receive oxygen and nutrients

A

Endocardium

26
Q

Progressive subendocardial ischemia and injury may progress to a subendocardial myoinfarct called what?

A

Non-Q wave infarction

27
Q

Flat ST segment depression results from _____

A

Subendocardial infarct or injury

28
Q

What does ST elevation indicate?

A

Myocardial injury or infarct in progress

29
Q

ST segment elevation also seen in:

A
  • Ventricular hypertrophy
  • Conductiion abn
  • PE
  • Spont pneump
  • Intracranial hemorrhage
  • HyperK
  • Pericarditis (seen in many leads)
30
Q

What indicates the presence of irreversible myocardial damage or myocardial infarction?

A

Pathological Q waves

31
Q

What are pathologic Q waves

A

> 0.04s

  • At least 1/3 the ht of R wave in same QRS
  • Present in 2 + leads
32
Q

Why do pathologic Q waves dev?

A
  • Infarcted areas of heart become electrically SILENT
  • Take hrs or days to dev
  • May persist for life
33
Q

MI will less damage vs more damage

A

Q wave –> more extensive damage

34
Q

Will you always have Q waves with MI?

A

No, you can only have ST-T changes, but no q waves

35
Q

Rt coronary artery perfuses what?

A
  • Rt atrium
  • Rt ventricle
  • Inferior and posterior walls of Lt ventricle
36
Q

Left main coronary artery divides into what

A

Lt anterior descending and Lt circumflex

37
Q

LAD perfuses

A
  • anterior and lateral left ventricle
  • anterior 2/3 of ventricular septum
  • R and L bundle branches
38
Q

LCX perfuses

A
  • L atrium, anterolateral, posterolateral and posterior LV
39
Q

Anterior MI

A
  • changes is percordial (V1-4) with reciprocal changes in inferior leads
40
Q

Lateral MI

A
  • changes in lead I, aVL, V5 & 6, reciprocal changes in inferior leads
41
Q

Inferior MI

A

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

42
Q

Posterior MI

A
  • Reciprocal changes in V1 and 2

- Tall R waves with ST depression in theses leads

43
Q

EKG Evolution in Q wave MI

A
  1. Normal
  2. Hyperacute T wave changes with ST elevation
  3. Marked ST elevation with 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
44
Q

Septal MI

A

V1-2

45
Q

Anteroseptal MI

A

V1-3

46
Q

Anterolateral MI

A

V1 or 2 to V5 or 6

47
Q

How do you tell a new vs old MI?

A

Q wave in the absence of ST segment and T wave abn indicates healed or old infarct

48
Q

What is the criteria for an abn R wave in posterior MI?

A
  • Duration >/= 0.04s
  • R >/= S
  • Pt > 30 yo
  • No signs of RVH

EKG (5 decks)

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