Acute Myocardial Infarction

Question 1

What factors affect the hearts energy supply and viability?

Answer 1

1) Coronary blood flow
2) Sympathetic nerves (NAdr/Adr increase firing rate and force)
3) CVP (preload) sets ventricular pressure and hence inotropic state by starling’s law (increase pressure, increase area, increase stretch).

Question 2

What factors IMPROVE the energy status of the ventricles?

Answer 2

1) Increased coronary blood flow (increase energy supply)

2) Decrease after-load, pre-load and having a negative inotropy (decrease energy demand).

Question 3

IHD; what is it, what causes it, what are the symptoms and why can it cause death?

Answer 3

Ischemic heart disease, it is caused by coronary atherosclerosis and thrombosis. Symptoms are angina caused by increased sympathetic drive (exercise) and it causes 40% of deaths in the UK from VF, HF or stroke.

Question 4

Define acute myocardial infarction

Answer 4

the first few hours following a heart attack

Question 5

Define heart attack

Answer 5

sudden and symptomatic episode of acute myocardial ischemia in patients with IHD.

Question 6

What are the effects of acute myocardial ischemia in IHD?

Answer 6

Angina, arrythmias, MI (cell death) and coronary vasospam which is alleviated by REPERFUSION.

Question 7

How can you treat acute MI (paramedics/immediately on hospitalisation)?

Answer 7

Morphine (iv) to alleviate angina and stress related catecholamines BUT patients become nauseated.

Reperfusion within 3 hours is essential.

• thrombolytics iv facilitate reperfusion
• –tpa
• –recombinant tpa (££)
• –streptokinase
• –heparin - enhances antithrombin III activity therefore inhibiting thrombin activity
• –adenosine to limit infarct size

Question 8

How would you then treat MI in hospital? (Arrythmias and cardiogenic shock)

Answer 8

Arrythmias; electrical defibrilation (to terminate VF)
Cardiogenic shock (acute HF)
-Beta agonists eg dobutamine.

Question 9

What prophylaqxis would you give someone after their first MI?

Answer 9

Aspirin
Beta-blockers - prevent the adverse remodelling of the heart which would normally result in an increased sympathetic drive (increased heart size) beta blockers decrease this remodelling
They also decrease long term mortality.
B1: Metoprolol
B1&2: Propranolol
B1,2 and A1: Carvedilol