Acute myocardial infarction

Question 1

Briefly describe the pathology of acute myocardial infarction.

Answer 1

Heart attack that is caused by a blockage of blood flow in one/multiple coronary vessels to heart
- usually caused by a blood clot.

Can be classified by STEMI or Non-STEMI:
STEMI - results from complete blockage of blood flow of coronary artery
NSTEMI - partial blockage of coronary artery

Question 2

Briefly describe the pathophysiology of acute MI.

Answer 2

Loss of blood flow to the myocardium causes the heart muscle to fail.
- without oxygen (+ production of ATP energy), the heart tissue is unable to keep functioning (pumping) and will eventually die –> tissue death

• tissue damage in the heart –> abnormal heart rhythms (arrhythmias)
• heart running low on oxygen - sends pain signals to the brain –> severe central pain

Question 3

What are the symptoms?

Answer 3

Severe, crushing, substernal pain of abrupt onset, often radiating to the left arm, neck, or jaw
- heart muscle not receiving oxygenated blood (cramp) - send pain signals to the brain as heart running low on oxygen

Dyspnoea/SOB - heart not pumping properly and fluid can back up into the lung (oedema)

Confusion - nerves connected to heart same as nerve connected to arm

Dizziness - lack of oxygen reaching the brain.

Racing heart

• adrenaline sent from the brain
• patch of cardiomyocytes stops beating - rest of the heart has to beat faster to compensate for the cardiomyocytes that stopped beating

Question 4

What are the signs?

Answer 4

- Pale, cool, and moist skin
•Tachycardia/arrhythmias
• Hyper/hypotension
• Syncope (fainting)
• Elevated cardiac enzymes (e.g. troponin) - cardiac muscle damaged and is not getting enough oxygen 

• Angiogram: blocked coronary arteries
• CXR signs: pulmonary oedema if reduced heart function (e.g. LV affected)

Question 5

What are the findings from a physiotherapy objective assessment?

Answer 5

Obs:

• pale, cool, and moist skin
• vomiting

Palpations:

• tachycardia (fast HR)
• arrhythmias (abnormal heart rhythm)

Question 6

What CXR features might be present for someone with acute MI?

Answer 6

Pulmonary oedema if reduced heart function

e. g. left ventricle affected - oxygen from heart to body
- blood is transferred back to the lungs

Question 7

What features might you see on an ECG?

Answer 7

NSTEMI:
Depressed ST wave or T-wave inversion - partial thickness infarct of the heart
No progression to Q wave

STEMI:
Elevated ST wave - full thickness infarct
Progression to Q wave

Question 8

What might you hear if you auscultated this patient?

Answer 8

Heart murmurs:

• caused by a swooshing of blood flow in the heart
• improper blood circulation
• can be caused by arrhythmic heart pumping

Question 9

What findings on a blood test would suggest myocardial infarction?

Answer 9

Looking for cardiac biomarkers:
Elevated Tnt (troponin T) levels exclusive to the heart muscle
- normal TnT is 3-14 ng/L, >15 is considered elevated, >30 in Sx indicates MI
- TnT is the cardiac-specific protein that is released when the heart muscle has been damaged

Question 10

Ask two questions to obtain more information about the symptoms.

Answer 10

Does your chest pain radiate to any other parts of your body?
How would you describe the chest pain? Is it like a crushing pain? Or a burning sensation?
How long does the chest pain last for?