Coronary Artery Disease

Question 1

39 y.o. Asian man admitted to the medical admissions unit with pains in his chest and neck.

He admitted to smoking 20 cigarettes/day, and blood cholesterol had been measured at 7.2 mmol/L. His average HR on admission was 90 bpm and his BP was 170/100 mmHg.

An initial dx of unstable angina was made.

Answer 1

-

Question 2

a) what are his risk factors for coronary artery disease? list 4

Answer 2

• Asian ethnicity
• smoker
• hypercholesterolaemia
• HTN
• male

Question 3

b) you decide to admit him to hospital. what drug therapy could he be started on? list 4 potentially beneficial drugs and give a reason for prescribing each.

Answer 3

• aspirin: antiplatelet, ↓mortality
• clopidogrel: antiplatelet, ↓mortality
• simvastatin: ↓cholesterol, ↓mortality
• ramipril: ↓BP, ↓mortality
• atenolol: ↓BP, HR and controls angina
• amlodipine: ↓BP by vasodilation and controls angina
• morphine: controls pain, helps pt feel at ease
• nitrates: ↓BP by vasodilation (↓afterload), venodilation (↓preload) and controls angina

Question 4

c) list the 2 cardinal ECG features on the anterior chest leads of an acute full thickness anterior MI and outline their electrophysiological cause.

Answer 4

1) ST elevation
- normal muscle is polarised (normal-potential) during diastole and only depolarised during the action potential.
- however, MI triggers depolarisation of the muscle with resetting of the baseline of the affected leads causing abnormal currents to flow between adjacent depolarised and polarised tissues i.e. “current of injury”

2) pathological Q waves
- an initial downward movement of the QRS
- occurs after an MI and have a width of ≥1 small box and a depth >25% of the total QRS height
- occur due to the “myocardial window” i.e. the area of old MI is electrically silent and acts as a window = lead recording from that site sees activity from the opposite side of the heart, which is moving away from the lead, causing a downward deflection (Q wave)

Question 5

d) 6 months later he is admitted with further chest pain. a dx of unstable angina is made. what are the indications for CABG?

Answer 5

1) triple vessel disease
2) severe left main stem artery stenosis
3) co-existing left LV dysfunction or DM – CABG>PCI

Question 6

e) what vessels may a cardiac surgeon use as a graft to bypass an obstructing lesion?

Answer 6

1) long saphenous vein

2) left internal mammary artery (LIMA)