ACUTE CORONARY SYNDROME

Question 1

Define myocardial infarction.

Answer 1

Injury to the myocardium due to a lack of oxygen as a result of blood not flowing properly through the coronary arteries.

Question 2

What are the three conditions that fall under the umbrella term ‘acute coronary syndrome’ (ACS)?

Answer 2

ST elevated myocardial infarction (STEMI)
Non ST elevated myocardial infarction (NSTEMI)
Unstable angina

Question 3

What symptoms might a patient with suspected ACS present? (Name at least 4)

Answer 3

Central crushing chest pain
Pain radiating to left arm, neck, jaw, back and upper abdomen
Sweatiness
Cold extremities
Palpitations
Nausea
Shortness of breath (usually occurs later)

Question 4

What signs might a patient with suspected ACS present with? (Name at least 4)

Answer 4

Distress
Pallor
Sweatiness
Tachycardia (or sometimes bradycardia)
Increased or decreased blood pressure
Additional heart sound
Bi-basal crepitations
Raised JVP
Pan-systolic murmur

Question 5

What tests would need to be done to confirm a diagnosis of STEMI? What results would the tests yield?

Answer 5

ECG showing either ST elevation or new left bundle branch block.
Blood test showing elevating cardiac markers

Question 6

Other than ST-elevation, what else might be seen on an ECG of a patient having a STEMI?

Answer 6

Hyperacute T waves
T wave inversion
Pathological Q wave
ST depression in opposing leads

Question 7

What might be seen on the ECG of a patient having a NSTEMI?

Answer 7

ST depression
Hyperacute T waves
T wave inversion
Pathological Q wave

Question 8

What is the diagnostic difference between unstable angina and a NSTEMI?

Answer 8

Unstable angina will not show a raise in cardiac markers such as troponin.

Question 9

What is the underlying pathology of a STEMI?

Answer 9

A STEMI is caused by a complete blockage of one of the three main coronary arteries (left anterior descending, circumflex and right coronary artery). The blockage is usually caused by a white arterial thrombus, made of white blood cells, cholesterol and fat.

Question 10

What is the underlying pathology of a NSTEMI?

Answer 10

A NSTEMI is caused by either a partial occlusion of a major coronary artery or a complete occlusion of a minor coronary artery (thereby affecting a smaller area).

Question 11

What are the risk factors associated with ACS? (Name at least 5)

Answer 11

Gender - being male
Age - over 55
Family history of heart disease under 55
Premature menopause
Diabetes
Smoking
Hypertension
Hyperlipidaemia
Hypercholesterolaemia
Obesity
Sedentary lifestyle
Cocaine use
Stress (controversial)

Question 12

What is the GRACE score and what is it used for?

Answer 12

The GRACE score is a prospectively studied scoring system to risk stratify patients with diagnosed ACS to estimate their in-hospital and 6 month to 3 year mortality. It may be used to assess which treatment option is used for a patient with diagnosed NSTEMI.
The GRACE score takes into account the patient’s age, HR, systolic BP, creatinine level, whether there was cardiac arrest at admission, ST deviation, elevated or abnormal cardiac enzymes and whether there are any signs of heart failure, cardiogenic shock and pulmonary oedema.

Question 13

How does atherosclerosis lead to a myocardial infarction?

Answer 13

Atherosclerotic plaque slowly builds up in the inner lining of a coronary artery and then suddenly ruptures, causing catastrophic thrombus formation through platelet aggregation, totally occluding the artery and preventing blood flow downstream.

Question 14

What is the difference between a transmural myocardial infarction and a subendocardial myocardial infarction? Which might be more dangerous and why?

Answer 14

Ischemia of the myocardium which extends to the endocardium and disrupts the inner lining of the heart is called a “transmural” infarction.

Less extensive infarctions are often “subendocardial” and do not affect the epicardium.

Subendocardial infarctions are much more dangerous than transmural infarctions because they create an area of dead tissue surrounded by a boundary region of damaged myocytes. This damaged region will still conduct impulses but more slowly, resulting in irregular rhythms. The damaged region may enlarge or extend and become more life-threatening.

Question 15

What are the possible complications following a MI? (Name at least 4)

Answer 15

Cardiac arrest
Congestive heart failure
Myocardial rupture
Arrhythmia
Pericarditis
Cardiogenic shock

Question 16

Which myocardial region(s) does the left anterior descending artery supply?

Answer 16

Anteroseptal and anterolapical regions

Question 17

Which myocardial region(s) does the circumflex artery supply (in the majority of people)?

Answer 17

Anterolateral region

Question 18

Which myocardial region(s) does the right coronary artery supply (in the majority of people)?

Answer 18

Inferior and posterior regions

Question 19

What determines coronary dominance?

Answer 19

The artery that supplies the posterior descending artery determines coronary dominance.
If the posterior descending artery is supplied by the right coronary artery (RCA), then the coronary circulation can be classified as “right-dominant”.
If the posterior descending artery is supplied by the circumflex artery (CX), a branch of the left artery, then the coronary circulation can be classified as “left-dominant”.
If the posterior descending artery is supplied by both the right coronary artery and the circumflex artery, then the coronary circulation can be classified as “co-dominant”.

A precise anatomic definition of dominance would be the artery which gives off supply to the AV node.

Question 20

With regard to coronary dominance, what percentage of the population are right-dominant?

Answer 20

About 70%

Question 21

With regard to coronary dominance, what percentage of the population are left-dominant?

Answer 21

About 10%

Question 22

With regard to coronary dominance, what percentage of the population are co-dominant?

Answer 22

About 20%

Question 23

What tests and investigations should be arranged for someone with suspected ACS?

Answer 23

ECG

Blood tests: FBC, U&E, glucose, lipids, cardiac enzymes (eg troponin and creatinine kinase CK-MB and myoglobin)

Question 24

What is differential diagnosis of someone presenting with the signs and symptoms of ACS? (Name at least 4)

Answer 24

Angina
Pericarditis
Myocarditis
Aortic dissection
Pulmonary embolism
Oesophageal reflux
Costochondritis

Question 25

What is the gold standard treatment for someone having a STEMI?

Answer 25

Percutaneous coronary intervention (angioplasty)

Question 26

What might be given to someone when they first present with the symptoms of ACS?

Answer 26

MONA - 
Morphine
Oxygen
Nitrates
Aspirin (300 mg)

Question 27

What medications would be given to someone post initial treatment for a STEMI? Can you an example of the drug with an appropriate dose?

Answer 27

Beta blocker - Bisoprolol 10 mg OD
ACE inhibitor - Ramipril 5 mg BD
Dual antiplatelet therapy - Aspirin 75 mg OD, Ticagrelor 90 mg BD
Statin - Simvastatin max 80 mg OD
Nitrates - GTN spray PRN

Question 28

On an ECG which leads correspond to the anteroseptal leads? What does ST elevation in these leads indicate?

Answer 28

V1 and V2

Left anterior descending artery occlusion

Question 29

On an ECG which leads correspond to the anterior leads? What does ST elevation in these leads indicate?

Answer 29

V2-V4

Left anterior descending artery occlusion

Question 30

On an ECG which leads correspond to the lateral leads? What does ST elevation in these leads indicate?

Answer 30

V5 and V6

Circumflex artery occlusion

Question 31

On an ECG which leads correspond to the inferior leads? What does ST elevation in these leads indicate?

Answer 31

II, III and aVF

Right coronary artery occlusion

Question 32

Depression is another complication of an episode of MI. Which SSRI is classically prescribed for an ACS patient diagnosed with depression?

Answer 32

Sertraline