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Flashcards in Lecture 7 Deck (48)
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1

______ deliver blood to myocardial cells

Coronary Arteries

2

______ return deoxygenated blood to RA via coronary sinus

Coronary Veins

3

Q wave

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

4

ST segment

- Flat line that follows the QRS complex and connects it to T wave

5

T wave

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

6

Myocardial ischemia

- Can be reversed if supply of oxygen and nutrients is restored
- T wave and ST segment changes
- NO permanent damage

7

Where are the coronary arteries?

Epicardial surface of the heart

8

Where does myocardial ischemia generally appear first?

Sub-endocardial region

9

Causes of Myocardial Ischemia

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

10

Examples findings that are Not MIs (6)

- Subendocardial ischemia
- Transient ST depression
- New onset angina
- Transmural ischemia
- Transient ST elevation
- Variant angina

11

No Q MI (2)

- Non-ST elevation MI
- ST depression or T wave changes or normal ECG

12

Q wave MI (2)

- ST elevation MI
- Typical evolution of ST-T changes

13

Myocardial injury

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

14

Mycardial infarction

- 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)

15

Direction of Depolarization

- Normally proceeds in an endocardial to epicardial direction

16

Where is the conduction system?

Subendocardial tissue

17

Direction of Repolarization

- Repolarization usually proceeds from an epicardial to endocardial direction

18

Where is the coronary circulation system?

Epicardial surface

19

Characteristics of Myocardial Ischemia

- Inverted T waves
- Tall, peaked T wave
- Depressed ST segement

20

Transmural Ischemia

- 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

T wave inversion

- 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

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

- May be seen in early stages of acute MI
- > 6mm in limb leads
- > 12 mm in precord

23

ST Segment depression

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

24

Subendocardial Ischemia

- Inner layer of the heart and does not extend through entire ventricular wall

25

What is the last place to receive oxygen and nutrients

Endocardium

26

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

Non-Q wave infarction

27

Flat ST segment depression results from _____

Subendocardial infarct or injury

28

What does ST elevation indicate?

Myocardial injury or infarct in progress

29

ST segment elevation also seen in:

- Ventricular hypertrophy
- Conductiion abn
- PE
- Spont pneump
- Intracranial hemorrhage
- HyperK
- Pericarditis (seen in many leads)

30

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

Pathological Q waves