Myocardial Infarction/Acute Coronary Syndrome

Question 1

How common is it?

Answer 1

Very common basically.

Question 2

Who does it affect?

Answer 2

• Most occur in people aged over 50 and it becomes more common with increasing age. Sometimes younger people are affected. More common in men.
• After menopause, gender risk is the same.

Question 3

What causes it?

Answer 3

• Narrowing of coronary arteries as a result of coronary atheroma leads to blockage of coronary artery due to blood clot (coronary thrombosis). Reduced delivery of blood with oxygen and nutrients to myocardial tissues leads to ischaemia and necrosis.
• Impaired contraction of myocardium, abnormal electrical activity of heart cells.

Question 4

What risk factors are there (and how can they be

reduced)?

Answer 4

• Smoking, hypertension, high cholesterol, high blood sugar/diabetes, low exercise, obesity. (Smoking cessation, medication (BP, statins, metformin), improved diet/exercise.)
• Family history of heart disease.
• Age/Male gender.

Question 5

How does it present?

Answer 5

• Symptoms – severe crushing central/generalised chest pain – sudden onset. Pain radiates to arms and neck. Associated symptoms such as nausea, vomiting, sweating and breathlessness.
• Signs – Patient distressed due to pain. Blood pressure low and HR fast. Breathlessness may be obvious with fluid heard on lungs during inspiration due to pulmonary oedema.

Question 6

Which other conditions may present similarly?

Answer 6

• Chest pain - angina, pericarditis, aortic dissection, pneumothorax, oesophageal spasm, musculoskeletal pain.
• Breathlessness – heart failure, angina, PE, pulmonary hypertension, respiratory disease.
• GI - gastro-oesophageal reflux, acute gastritis, cholecystitis, pancreatitis.

Question 7

How would you investigate the patient?

Answer 7

• Serial ECGs - new ST segment elevation; initially peaked T waves and then T-wave inversion; new Q waves; new conduction defects.
• Cardiac enzymes – troponins T and I highly sensitive for cardiac damage. Serum levels increase within 3-12 hours from the onset of chest pain, peak at 24-48 hours, and return to baseline over 5-14 days. Creatine kinase levels increase within 3-12 hours of onset of chest pain, reach peak values within 24 hours, and return to baseline after 48-72 hours.
• FBC to rule out anaemia – leucocytosis common. - Monitor potassium levels.
• CRP and other markers of inflammation.
• CXR to assess heart size – Hf and pulmonary oedema.
• Angiography – Defines patient’s coronary anatomy and the extend of the disease.
• Echocardiography - define the extent of the infarction and assess overall ventricular function and can identify complications. - Myocardial perfusion scintigraphy using single photon emission computed tomography (SPECT).

Question 8

What treatment/s would you consider? What risks

and benefits of treatment are there? (Acute)

Answer 8

• Acute – Pain relief with morphine, administration of high-flow oxygen, oral aspirin treatment. Thrombolytic drugs largely replaced by Primary Percutaneous Intervention (stenting).

Question 9

Which enzymes are raised in MI?

Answer 9

• Troponins T and I raised within 3-12 hours of onset of chest pain, peak at 24-48 hours, and return to baseline over 5-14 days.
• CK levels increase within 3-12 hours of onset, peak at 24, return to baseline after 48-72 hours.

Question 10

What treatment/s would you consider? What risks

and benefits of treatment are there? (Primary/Secondary prevention)

Answer 10

• Primary and secondary prevention – Aspirin – antiplatelet action. Clopidogrel – antiplatelet action. Beta blockers – lower heart rate and blood pressure. Statins – HMG CoA reducatase inhibitor, reduces cholesterol. ACE-inhibitors – reduce blood pressure. ARBs, calcium channel blockers etc.