Myocardial Infarction

Question 1

What is the first step in diagnosing acute MI?

Answer 1

ECG

Question 2

What is the crucial part of the ECG to diagnosing MI?

Answer 2

ST segment

Question 3

What should the normal ST segment look like?

Answer 3

Should be the same height as the PR interval and the isoelectric line

Question 4

What happens to the ST segment in an MI?

Answer 4

ST elevation

Question 5

What else is used to diagnose MI and why?

Answer 5

The presence of troponin I or T (cardiac specific) as when heart cells burst/die these proteins are released

Question 6

What is the coronary flow reserve?

Answer 6

Maximum amount of blood in the coronary blood flow

Question 7

By how much can the coronary flow reserve increase?

Answer 7

5 fold

Question 8

Why does angina happen on exertion?

Answer 8

Bc stenosis affects coronary flow reserve

Question 9

When does coronary flow reserve increase normally?

Answer 9

During exercise

Question 10

How does stenosis affect coronary blood flow?

Answer 10

After about 50% stenosis, the coronary flow reserve decreases so coronary blood flow can no longer increase as much - CFR decreases with increasing % stenosis

Question 11

What causes the stenosis to increase from 50% to 100% in AMI?

Answer 11

Unstable clot/plaque - RBCs caught in fibrin net

Question 12

What is chest pain due to in AMI?

Answer 12

Sensation of myocardial ischaemia

Question 13

Where else is pain felt during an AMI?

Answer 13

Anterior chest, left arm, neck

Question 14

Is the pain diffuse or localised and why?

Answer 14

Diffuse → nerve supply is somatic, no dermatomes, visceral nerve supply

Question 15

What is the character of pain in AMI?

Answer 15

Tight, pressure, weight, constriction, dull

Question 16

What triggers angina?

Answer 16

Exercise, cold, meals, psychological stress

Question 17

What is relief for angina?

Answer 17

Rest, GTN

Question 18

What causes shortness of breath in an MI?

Answer 18

Pulmonary oedema

Question 19

What happens as the heart becomes increasing failing?

Answer 19

As LV EDP increases, CO increases less

Question 20

Why does oedema occur?

Answer 20

Pressure on the venule end of capillaries → mean pressure increases → hydrostatic pressure increases

Question 21

What happens when atherosclerotic plaque ruptures?

Answer 21

1) Endothelial layer feels back under sheer stress of exercise
2) Platelets starts accumulating on exposed atherosclerotic plaque which initiates the clotting casade

Question 22

What is the difference between stable and unstable atherosclerotic plaque?

Answer 22

Stable plaque is separated from the lumen by a fibrous cap however in unstable plaque the fibrous cap is eroded

Question 23

What state is the plaque in at body temp?

Answer 23

Liquid

Question 24

What happens to unstable plaque?

Answer 24

1) Fibrous cap is eroded and communicated with the lumen
2) Cholesterol liquid is replaced by a blood clot
3) Intraplaque haemorrhage occurs which extends into the lumen of the coronary artery

Question 25

What are 3 treatments for atherosclerotic plaque?

Answer 25

1) Statins (cholesterol lowering) 2) Anti-platelet drugs 3) Clot busters

Question 26

How does cholesterol cause plaque?

Answer 26

1) Oxidised LDL is attacked by macrophages which think it is a foreign body 2) Activated macrophages induce intimal smooth muscle cell death and degrade matrix in the fibrous cap 3) Intimal smooth muscle cells become senescent

Question 27

What drugs are used to lower LDL cholesterol by preventing the above process?

Answer 27

Statins

Question 28

Why do you need anti-platelet drugs to treat plaque?

Answer 28

Because platelets aggregate at the site of rupture/erosin

Question 29

What are anti-platelet drugs?

Answer 29

Aspirin and other drugs which work together with aspirin

Question 30

When is aspirin given to treat AMI?

Answer 30

Immediately after ST elevation is seen on ECG (done in ambulance)

Question 31

How much aspirin is given and how?

Answer 31

300mg orally (bc it is absorbed in buccal mucosa)

Question 32

What happens after platelets aggregate at the site of rupture?

Answer 32

Thrombus forms and extends into the lumen and plaque

Question 33

What is an example of a clot buster drug (thrombolytic) used for PE and stroke?

Answer 33

tPA (tissue plasminogen activator)

Question 34

What is the problem with used a thrombolytic e.g. tPA?

Answer 34

You are marinating the body in a v potent drug which goes around the whole body and stops clotting aka the healing process around the body → risk of GI and intracranial haemorrhage

Question 35

What happens when MI patient arrives at hospital?

Answer 35

Go to heart attack centre and direct to catheter labs for mechanical reperfusion (bypass A&E) bc time is muscle

Question 36

Why is mechanical reperfusion better than pharmacological?

Answer 36

1) Faster reperfusion 2) Higher % reperfusion 3) Less stroke and bleeds 4) Lower mortality

Question 37

What is mechanical reperfusion?

Answer 37

Inserting a stent?

Question 38

What is the name of the mechanical reperfusion process used to treat MI?

Answer 38

Primary percutaneous coronary intervention

Question 39

What is the most common presentation of AMI?

Answer 39

Chest pain

Question 40

What are the two main types of MI?

Answer 40

1) STEMI (ST elevated MI) | 2) NSTEMI (non-ST elevated MI)

Question 41

Which type of MI is more serious?

Answer 41

STEMI

Question 42

What are the two most important investigations when suspecting an MI?

Answer 42

ECG and troponin

Question 43

What is used to diagnose a NSTEMI without ST elevation?

Answer 43

Troponin release

Question 44

What is the diagnosis if there is no ST elevation and the troponin is negative?

Answer 44

Unstable angina

Question 45

What is the diagnosis if there is ST elevation but the troponin is negative?

Answer 45

Aborted MI (v rare)

Question 46

What do you do if someone has ST elevation?

Answer 46

Risk of MI but heart is in process of dying → medical emergency, take straight to cath lab for mechanical reperfusion

Question 47

What do you do if someone has no ST elevation?

Answer 47

No occluded epicardial coronary artery so not a medical emergency until troponin comes back positive

Question 48

How long does it take for troponin results to come back?

Answer 48

60 minutes

Question 49

What do you need before making diagnosis of MI?

Answer 49

Troponin release shown

Question 50

What is a myocardial infarction?

Answer 50

When there is evidence of myocardial necrosis in a clinical setting consistent with myocardial ischaemia

Question 51

How do you diagnose MI?

Answer 51

- Detection of rise and/or fall of cardiac biomarkers (troponin) with at least one value >99th percentile of the URL together with evidence of myocardial ischaemia with at least one of... 1) Symptoms of ischaemia 2) ECG changes indicative of new ischaemia (ST or LBBB) 3) Development of pathological Q waves 4) Imaging evidence of new loss of viable myocardium or new regional wall motion abnormality 5) Identification of intracoronary thrombus by angiography or autopsy

Question 52

What are the types of MI?

Answer 52

1) Spontaneous MI (plaque rupture, ulceration, erosion or dissection) 2) MI secondary to ischaemic imbalance (endothelial dysfunction, spasm, coronary embolism, fast or slow arrhythmias, anaemia, hypoxia, hypotension, high BP ± LVH (perioperative)) 3) MI causing death before biomarkers available 4a) MI related to PCI 4b) MI related to stent thrombosis 5) MI related to CBG

Question 53

What causes don't lead to an MI?

Answer 53

Myocarditis, chemotherapy, cardioversion, trauma

Question 54

What drugs improve supply demand balance of the heart?

Answer 54

Anti-anginals 1) Beta-adrenoreceptor blockers 2) L-type calcium channel blockers 3) Nitrates 4) ATP-sensitive potassium channel openers 5) Funny current channel blockers

Question 55

What needs to happen/be given to stop a second heart attack or developing heart failure?

Answer 55

1) Lower cholesterol 2) Lower BP (ACE-I and beta blocker) 3) Aspirin ± ADP receptor antagonist → stops platelet activation 4) Beta blockers 5) Statins 6) Stopping smoking 7) Managing diabetes

Question 56

What are examples of the big 5 classes of cardiology drugs which prolong life (secondary intervention?

Answer 56

1) Atorvastatin 2) Ramipril 3) Bisoprolol 4) Aspirin 5) Ticagrelor

Question 57

Give an example of an ACE inhibitor

Answer 57

Ramipril

Question 58

Give an example of a beta blocker

Answer 58

Bisoprolol

Question 59

Give an example of a platelet ADP receptor antagonist

Answer 59

Ticagrelor

Question 60

Given an example of a statin

Answer 60

Atorvastatin

Question 61

What investigation usually leads to patients being advised to take statins?

Answer 61

CT coronary angiogram

Question 62

What happens to the heart after an MI?

Answer 62

The heart dilates

Question 63

What happens hours to days after an MI?

Answer 63

Expansion of infarct (ventricular remodelling)

Question 64

What happens days to months after an MI?

Answer 64

Global (ventricular) remodelling

Question 65

What accelerates ventricular modelling (heart dilation)?

Answer 65

Further plaque rupture

Question 66

What happens to the cardiac wall after an MI?

Answer 66

The wall of the apex of the heart is much thinner after one apical anterior MI due to cardiac dilation? (good areas are those away from the area of infarction)

Question 67

How many people in the UK aged >45 have definite HF?

Answer 67

650,000

Question 68

What is the readmission rate in older patients?

Answer 68

Up to 50% in 6 months following discharge §

Question 69

What are the non-modifiable CV risk factors?

Answer 69

Family history, age, sex

Question 70

What are the modifiable CV risk factors?

Answer 70

Smoking, high cholesterol, high BP, diabetes, obesity, diet, exercise, excess alcohol