Myocardial Infarction

Question 1

Which artery is most commonly affected with death from MI?

Answer 1

Widowmaker - LAD

Question 2

Symptoms

Answer 2

severe crushing chest pain - sudden onset
pain radiating to arms/neck
nausea, vomiting, sweatiness, breathlessness

Question 3

Signs

Answer 3

Patient is distressed due to pain
Low BP
Tachycardia
Pulmonary oedema

Question 4

What is angina?

Answer 4

Pain in the centre of the chest that may radiate to arms/jaw
Induced by exercise and relieved by rest

Occurs when demand for blood by the heart exceeds the supply of the coronary arteries

Question 5

Risk factors for MI

Answer 5

family history
male
smoking
high cholesterol
diabetes
low exercise
obesity
hypertension
high blood sugar

Question 6

Physiological abnormalities

Answer 6

Ischaemia leading to necrosiss
Impaired contraction
abnormal electrical activity

Question 7

What is Virchow’s triad?

Answer 7

Changes in blood flow
Changes in vessel wall
Changes in blood constituents

Question 8

Which aspects of Virchow’s triad is most relevant to MI?

Answer 8

Changes in vessel wall - atheroma

Question 9

Abnormal test results

Answer 9

ECG - ST segment elevation if coronary artery completely blocked

Blood tests - raised troponin

Echo - reduced contraction

Angiogram - artery blocked by atheroma and thrombosis

Question 10

Why is troponin high in MI?

Answer 10

Troponin is released from myocytes when they are irreversibly damaged - very specific to cardiac tissue

Question 11

Drugs used as primary prevention?

Answer 11

Aspirin - antiplatelet
Clopidogrel - antiplatelt
Beta-blockers - lower heart rate and blood pressure (block adrenaline and noradrenaline)
Statins - HMG-CoA reductase inhibitors that lower cholesterol
ACE-inhbitors - diuretics

Question 12

Medical treatment?

Answer 12

Morphine
high flow oxygen
thrombolytic drugs OR primary percutaneous intervention - balloon opens artery and stent placed in

Question 13

How does simvastatin works?

Answer 13

Blocls HMG CoA reductase which stops cholesterol forming in the liver

Question 14

At which sites do beta blockers work?

Answer 14

Beta 1 receptors in the brain
Myocardial beta 1 receptors to decrease force and rate of contraction
Renal beta 1 receptors to block release of renin and lower bp

Question 15

How do ACE inhibitors work?

Answer 15

block formation of angiotensin 1 from angiotensin 2 to prevent vasoconstriction

Question 16

Give a brief explanation of renin angiotensin system on blood pressure

Answer 16

Liver releases angiotensiongen
Kidney releases renin, which converts angiotensinogen into angiotensin 1
Lungs & kidney release ACE (angiotensin converting enzyme) which converts angiotensin I to angiotensin II
angiotensin II acts on arteries to cause vasoconstriction