Myocardial Infarction

Question 1

Which anatomical structures are affected in myocardial infarction?

Answer 1

The left coronary artery and its branches - left anterior descending (LAD), circumflex and left main stem

Right coronary artery - posterior descending artery

Question 2

What is the usual physiology of the coronary arteries?

Answer 2

They deliver blood carrying oxygen and nutrients to the myocardial tissues

Question 3

Which structural abnormalities can lead to myocardial infarction?

Answer 3

Narrowing of the arteries as a result of coronary atheroma

Coronary thrombosis

Question 4

What is coronary thrombosis?

Answer 4

Blockage of an artery due to a blood clot

Question 5

What physiological abnormalities occur as a result of myocardial infarction?

Answer 5

Ischaemia which eventually leads to necrosis of myocardium

Impaired contraction of myocardium

Abnormal electrical activity of heart cells

Question 6

In which groups of people is myocardial infarction more common?

Answer 6

More common in men and the elderly

Family history is usually present

Question 7

What are the risk factors for myocardial infarction?

Answer 7

1. smoking
2. high blood pressure
3. high cholesterol
4. high blood sugar/diabetes
5. low exercise
6. obesity

Question 8

What symptoms are experienced during a myocardial infarction?

Answer 8

Severe crushing central chest pain which is sudden in onset

The pain radiates to arm or neck

Associated nausea, vomiting, sweating and breathlessness

Question 9

What are the clinical signs of a patient with myocardial infarction?

Answer 9

Patient clearly distressed due to pain

Low blood pressure and fast heart rate

Breathlessness

Question 10

What clinical signs may be observed relating to the lungs?

Answer 10

Fluid may be heard on the lungs during inspiration

This is due to pulmonary oedema (fluid in alveoli)

Question 11

What will an ECG look like in a patient with MI?

Answer 11

It shows “ST elevation” if the coronary artery is completely blocked

Question 12

What will a blood test show in a patient with MI?

Answer 12

Raised levels of the heart protein troponin

Question 13

What will an echocardiogram of a patient with MI show?

Answer 13

Reduced contraction of the affected area

Question 14

What is a coronary angiogram and what may it show in a patient with MI?

Answer 14

X-ray of the heart arteries

Shows an artery blocked by atheromatous stenosis and by a blood clot (thrombosis)

Question 15

What immediate medical treatment is used to treat an MI patient?

Answer 15

1. morphine for pain relief
2. high-flow oxygen
3. oral aspirin treatment

Question 16

What have thrombolytic drugs been replaced by in treatment of MI?

Answer 16

Primary percutaneous intervention

Question 17

What is involved in primary percutaneous intervention?

Answer 17

a thin tube is inserted into the arm or leg to remove the clot

a small balloon is used to open the narrowed artery and a metal stent is placed there to hold the artery open

Question 18

What is the focus of primary and secondary prevention of MI?

Answer 18

Treatment or avoidance of risk factors

Question 19

Why is aspirin used to prevent MI?

Answer 19

It has antiplatelet action to prevent blood clots

Question 20

Why is clopidogrel used to prevent MI?

Answer 20

It has antiplatelet action to prevent blood clots, especially when a coronary stent is present

Question 21

Why are beta-blockers used to prevent MI?

Answer 21

They lower the heart rate and blood pressure through blocking the effects of adrenaline and noradrenaline

Question 22

Why are statins used to prevent MI?

Answer 22

They are HMG-CoA reductase inhibitors that lower blood cholesterol

Question 23

Why are ACE inhibitors used to treat MI?

Answer 23

They block angiotensin converting enzyme to prevent production of angiotensin II