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3.23 > Lecture 12: Acute Myocardial Infarction > Flashcards

Lecture 12: Acute Myocardial Infarction Flashcards

1
Q

What is myocardial infarction?

A

The interuption of blood supply to part of the heart, causing some heart cells to die

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2
Q

Where do thrombus form?

A

At the site of an atherosclerotic lesion, obstructing blood flow to the myocardial tissues

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3
Q

What can provide resistance to rupture?

A

Presence of smooth muscle cells in fibrous cap

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4
Q

What plaques are rupture prone?

A

Plaques rich in soft extracellular lipids

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5
Q

What is the triggering mechanism for the development of thrombus in patients with myocardial infarction?

A

Plaque rupture

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6
Q

What is infarct expansion?

A

A disproportionate thinning and dilation of the infarct zone

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7
Q

What is ventrical remodelling?

A

A disproportionate thinning and dilation of the ventricle resulting in an enlarged heart

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8
Q

What are the cellular changes associated with the initial myocardial infarction?

A
  • The development of infarct extension
  • Infarct expansion
  • Ventricular remodelling
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9
Q

What is a NSTEMI?

A

A complete occlusion of a minor coronary artery or a partial occlusion of a major coronary artery previously by atheroclosis.

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10
Q

What does a NSTEMI cause?

A

Causes a partial thickness damage of heart muscle

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11
Q

What is STEMI?

A

Occurs by developing a complete occlusion of a major coronary artery previeoisly affected by atherosclerosis

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12
Q

What does a STEMI cause?

A

Full thickness damage of heart muscle

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13
Q

What are the symptoms of myocardial infarction? (5)

A
  • Chest pain
  • Nausea
  • Vomiting
  • Sweating
  • Pain can radiate to neck, jaw, left arm, back
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14
Q

How do patients describe myocardial infarction?

A
  • Squeezing
  • Smothering
  • Choking sensations
  • Someone sitting on their chest
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15
Q

Is pain of myocardial infarction relieved by rest and sublingual GTN?

A

No

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16
Q

What causes GI complaints from myocardial infarction?

A

Due to sensitivity of pain and resulting vagal stimulation

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17
Q

How is acute MI diagnosed?

A
  • Biochemical markers
  • Laboratory tests
  • ECG
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18
Q

What are the biochemical markers used to diagnose MI

A
  • Rise and fall in troponin
  • Rapid rise and fall in creatine kinase
19
Q

What laboratory tests are used to diagnose MI?

A
  • Troponin I levels
20
Q

What is troponin?

A

Troponin T and I are components of the myofilament troponin complex. Released from damage

21
Q

Describe troponin I levels during a myocardial infarction

A
  • Rise in 3 hours
  • Peak at 14 to 18 hours
  • Remain elevated for 5-7 days
22
Q

Describe troponin T levels during MI

A

Rise in 3-5 hours and stay elevated for 10-14 days

23
Q

What are the iso forms of creatine kinase?

A
  • CK MB1
  • CK MB2
24
Q

Where is CK MB1 found?

25
Where is CK MB2 found?
Tissues
26
When does CK-MB appear in the serum?
6-12 hours
27
When does CK-MB peak?
Between 12 and 28 hours
28
When do CK-MB levels return to normal?
72 to 96 hours
29
What is myoglobin?
Oxygen binding protein
30
Where is myoglobin found?
Skeletal and cardiac muscle
31
When do myoglobin levels elevate?
Within 1-2 hours of MI
32
When do myoglobin levels peak?
3-15 hours
33
What is lactate dehydrogenase LDH?
A tetrametric protein, made up of two types of proteins
34
What happens to LDH during MI?
Levels elevate
35
Describe ECG during the early stage of MI?
- T waves become tall and narrow - This stage is referred to as hyper-acute or peaked T waves
36
What happens to the ST segment of an ECG during MI?
ST levels elevate
37
What do Q waves represent?
Flow of electrical forces towards the septum
38
What can a persistent elevation of ST segment indicate?
Presence of a ventricular aneurysm
39
What will always indicate previous myocardial infarction
Q waves - they never disappear
40
How does myocardial ischaemia affect ECG?
- ST segment depression - With or without T wave inversion as result of altered reploarizarion
41
How does myocardial injury affect ECG?
Causes ST segment elevation with or without loss of R wave
42
How does myocardial infarction affect ECG?
Causes deep Q waves of absence of depolarization current from dead tissue and receding currents from opposite side of heart
43
How long do Q waves take to develop?
Hours to days
44
What do Q waves show?
Presence of dead tissue and provide ECG evidence of a previous MI

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