Myocardial Infaction

Question 1

Definition of myocardial infarction

Answer 1

Supply demand imbalance

Question 2

What is the coronary blood supply & what side is mostly affected

Answer 2

1. Right coronary artery supplies right ventricle & posterior left ventricle
2. Left coronary artery has circumflex artery that supplies lateral left ventricle wall & left anterior descending artery that supples anterior left ventricle

Left side is mostly affected because highest metabolic activity

Question 3

3 factors impacting myocardial infarction severity

Answer 3

1. Which arteries are occluded
2. States of other arteries
3. How fast it happened = for collaterals to develop

Question 4

6 risk factors for myocardial infarction

Answer 4

Genetic factors
Smoking
Obesity
Diabetes
Hyperlipidaemia
Post menopause due to lower estrogen

Question 5

What is the main cause for myocardial infarction & explain

Answer 5

Coronary artery occlusion:
Atherosclerotic plaque ruptures, ulceration or haemorrhage & damage endothelial wall exposing subendothelium & activating coagulation cascade releasing platelets & microthrombi formation
Platelets release mediators that causes vasospasm
Microthrombi form thrombus & occlude artery

Question 6

3 other causes of myocardial infarction

Answer 6

1. Vasospasm: associated with platelet activation or drug use
2. Emboli: left sided mural thrombus as result of infective endocarditis or paradoxical emboli right side via defect
3. Infarction: amyloidosis, haematological abnormalities, vascular damage or vasculitis

Question 7

What is the two effect of ischameia & infarction

Answer 7

1. Transmural: single vessel blockage that is localised & well defined
2. Subendocardial/watershed zone: triple coronary artery narrowing/shock that globally decrease blood flow

Question 8

The 2 clinical presentation of myocardial infarction

Answer 8

Stable angina where present in exertion
Unstable angina where it is present at rest & exertion & results in syncope & collapse

Question 9

What is the complications of myocardial infarction (ACC VMPP)

Answer 9

Arrhythmia
Contractility dysfunction & cardiogenic shock (due to myocardial destruction)
Cardiac rupture (papillary muscle causing mitral regurgitation , left ventricle free wall causing cardiac tamponade & intraventricular septum)
Valve aneurysm (large transmural infarct complication)
Mural thrombus
Pericarditis (transmural infarct caused by inflammation of myocardium)
Progressive heart failure

Question 10

What is the 3 diagnostic criteria’s for of acute myocardial infarction

Answer 10

2/3:
Crushing chest pain
Changes in ECG
Increase in biomarkers

Question 11

What is the biomarkers of myocardial infarction

Answer 11

1. Myoglobin:
2. CK-MM & CK-M
3. Cardiac troponin T

Question 12

Definition angina pectoris

Answer 12

A clinical syndrome characterised by discomfort in the chest, jaw, shoulder, back or arm either during excretion or at rest

Question 13

What is the risk factors for angina pectoris

Answer 13

Obesity
HPT
Diabetes
Previous MI
Smoking
Male over 40 years
Post menopausal female

Question 14

Describe 3 other cause of angina pectoris

Answer 14

1. Anaemia due to decrease oxygen carrying capacity
2. Thyrotoxicosis due to high circulation of thyroid hormone creating an imbalance in oxygen carrying capability
3. Tachyarrythmias not allowing for coronary blood flow to occur during diastole

Question 15

Why is it important to manage angina pectoris

Answer 15

Prevent MI from occurring & reduce the symptoms to improve quality of life

Question 16

What is the management of angina pectoris (ABCDEF)

Answer 16

1. Aspirin & anti-anginals:
   Non selective COX inhibitor when prescribed at low dose that inhibits thromboxane formation & platelet aggregation (inhibit clot formation)
2. Beta blockers & BP:
   Decrease heart rate & cardiac contractility
   Reduce myocardial oxygen demand
3. Cholesterol & cigarettes
4. Diet & diabetes
5. Education & exercise
6. Follow up

Question 17

What is the main cause of angina pectoris

Answer 17

Atherosclerosis

Question 18

What can be given as a prophylaxis for angina pectoris & why

Answer 18

Nitrates that is a potent vasodilator that decrease preload & oxygen demand

Question 19

What is the 2 ways in which an atherosclerotic plaque forms

Answer 19

1. Slow occlusion of vessel causing angina
2. Acute MI due to lumen rupture & clot formation at damaged intima forming an acute occlusion

Question 20

What is the 5 managements of AMI

Answer 20

1. Oxygen
2. Anti-platelet therapy (aspirin)
3. Anti-coagulant (heparin)
4. Analgesia (morphine)
5. Revascularization via angioplasty or coronary bypass

Question 21

What is myoglobin used for & how long does it take to increase, peak & decrease

Answer 21

Used to rule out MI
Released from injured tissue after 1 hour (sensitive not specific)
Peak at 10hrs and decrease after 36hrs

Question 22

What is CK-MM/CK- MB used for & how long does it take to increase & decrease

Answer 22

CK-MB is cardiac specific & used to identify reinfarct
Increase after 6hrs & drop within 3-4 days

Question 23

What is cardiac troponin T used for & how long does it take to increase & decrease

Answer 23

cTns is specific to cardiac
Increase within 4-6 hrs until 10-14 days post MI

Question 24

What to do if a patient has changes in ECG & chest pain but negative troponin

Answer 24

Retest in a few hours as it is released after 4 - 6 hours