ischaemic heart disease

Question 1

Pathogenesis of IHD

Answer 1

1. Reduced coronary blood flow
2. Increased myocardial demand
3. Availability of O2 in blood

Question 2

4 clinical manifestations of IHD

Answer 2

1. Angina Pectoris
2. MI
3. Chronic Ischaemic Heart Disease with Heart Failure
4. Sudden Cardiac Failure

Question 3

What is angina pectoris?

Answer 3

• Episodic chest pain on exertion caused by transient ischaemia of the myocardium
• Relieved by rest or vasodilators

Question 4

What are the 3 types of angina pectoris?

Answer 4

1. Stable Angina
   - chest pain on exertion
   - can be relieved by rest or vasodilators
2. Prinzmetal Angina
   - due to arterial spasm
   - unrelated to physical activity, heart rate or BP
   - responds to vasodilators
3. Unstable Angina
   - pain precipitated by lower levels of activity/rest
   - does NOT get better with rest
   - minimal effect from vasodilators

Question 5

What are the early changes seen in myocardial ischaemia?

Answer 5

1. Cessation of aerobic metabolism within seconds leading to inadequate production of high energy phosphate (ATP)
2. Accumulation of noxious material eg Lactic Acid

As myocytes depend heavily on O2, severe ischaemia induces loss of contractility within 60s -> cessation of function can cause acute cardiac failure before myocytes completely dies

Question 6

Occlusion of LCA will lead to

Answer 6

antero-lateral MI

Question 7

Occlusion of LAD will lead to

Answer 7

antero-septal MI

Question 8

Occlusion of RCA will lead to

Answer 8

posterior MI

Question 9

Occlusion of LCX will lead to

Answer 9

lateral MI

Question 10

What are the clinical diagnosis of MI?

Answer 10

1. Symptoms: severe, crushing central chest pain that radiates to arm, neck with severe nausea and diaphoresis
2. ECG changes:
   - transmural infarct: STEMI
   - subendocardial infarct: NO STEMI
3. Elevated cardiac enzymes: troponin T, troponin I, creatine kinase M/B

Question 11

What is the morphology of MI at 0-12h?

Answer 11

no visible macroscopic changes but triphenyl tetrazolium test is possible (stains cardiac muscle but dead muscles are unable to pick up stain)

Question 12

What is the morphology of MI at 12-24h?

Answer 12

macroscopically: pale with blotchy discolouration
histologically: infarcted muscle brightly eosinophilic, loss of nuclei, intercellular oedema

Question 13

What is the morphology of MI at 24-72h?

Answer 13

macroscopically: soft, pale, yellow colour
histologically: neutrophilic infiltrate

Question 14

What is the morphology of MI at 3-10 days?

Answer 14

macroscopically: hyperaemic border around yellow area
histologically: granulation tissue forms

Question 15

What is the morphology of MI at 6-8 weeks?

Answer 15

fibrous scar forms

Question 16

What are the short term complications of MI?

Answer 16

• LV failure
• Arrhythmias
• Rupture myocardium -> blood leaks out of inner pericardium sac -> blood accumulates in pericardial sac -> increased pressure in pericardial sac -> puts pressure on the heart -> compromises in diastolic filling of the heart -> cardiac tamponade
• Thrombus formation
• Acute pericarditis
• Mitral valve incompetency

Question 17

What are the long term complications of MI?

Answer 17

• Left heart failure
• Aneurysm
• Recurrent MI
• Immune-mediated pericarditis

Question 18

What is chronic ischaemic heart disease with heart failure?

Answer 18

Chronic atherosclerotic narrowing of coronary arteries
Slow loss of myocardial fibres
Generalised myocardial fibrosis
Cardiac failure -> death

Question 19

What is the most common cause of sudden cardiac failure?

Answer 19

Ventricular fibrillation

Question 20

What are the other causes of sudden cardiac failure?

Answer 20

Pronounced stenosis of 1 or more major arteries
Acute plaque changes -> secondary thrombosis or massive MI