Ischemic Heart Disease

Question 1

Definition of ischemic heart disease

Answer 1

spectrum of disorders due to imbalance between

• myocardial metabolic demands
• coronary blood flow

Question 2

Causes of ischemic heart disease

Answer 2

1. Atherosclerosis (90-95%)
2. Others - embolism, ostial stenosis in syphilitic aortitis, dissecting aneurysms, direct trauma, arteritis, anomalous origin of LCA, hypoxemia

Question 3

Pathogenesis of IHD due to atherosclerosis (3)

Answer 3

1. Reduced coronary flow
   - chronic progressive atherosclerotic stenosis
   - 75% occlusion of coronary arterial lumen
   - possible acute plaque change
2. Increased myocardial demand
   - exercise, infection, pregnancy, hyperthyroidism, myocardial hypertrophy
3. Reduced availability of O2 in the blood - anemia, CO poisoning, pulm disease, L to R shunts

Question 4

Clinical manifestations of ischemic heart disease (4)

Answer 4

1. Angina pectoris (unstable/stable - acute/chronic)
2. Myocardial Infarction
3. Chronic IHD, cardiac failure
4. Sudden cardiac death

Question 5

Types of angina pectoris (3)

Answer 5

1. Stable Angina
2. Vasospastic/Variant Angina
3. Unstable Angina

Question 6

Features of stable angina

Answer 6

• due to chronic progressive coronary atherosclerosis stenosis
• episodic chest pain, usually due to increased demand
• modifiable with rest, drugs

Question 7

Features of vasospastic angina

Answer 7

• due to coronary artery spasm
• unrelated to physical activity, HR, BP
• episodic at rest

Question 8

Features of unstable angina

Answer 8

• due to acute plaque change + superimposed thrombosis, embolisation, vasospasm
• increasingly frequent/severe chest pain
• increased risk of MI, arrhythmia

Question 9

Definition of myocardial infarction

Answer 9

death of cardiac muscle following prolonged severe ischemia (impaired blood flow)

Question 10

Causes of myocardial infarction (2)

Answer 10

1. Regional MI (90%)
   - coronary artery occlusion
   - due to acute plaque event , thrombus formation, vasospasm
2. Circumferential subendocardial infarct
   - coronary artery occlusion in the absence of vascular pathology
   - general hypoperfusion (hypotension), vasospasm, emboli etc

Question 11

Morphology of myocardial infarction (5)

Answer 11

1. 0-12h
   - not visible
   - identified with tetrazolium chloride - non infarcted tissue turns black
2. 12-24h
   - G: pale, blotchy discolouration
   - M: infarcted muscle brightly eosinophilic, loss of nucleus, intercellular edema
3. 24-72h
   - G: soft, pale, yellow (exudate, necrotic material)
   - M: neutrophil infiltrate
4. 3-10d
   - G: hyperemic border around yellow area (body tries to localise)
   - M: granulation tissue response, macrophages
5. 6-8w
   - fibrous scar

Question 12

Clinical features of myocardial infarction (3)

Answer 12

1. Symptoms
   - chest pain not relieved by rest, rapid weak pulse, profuse sweating (diaphoresis), dyspnea
2. ECG changes
   - ST elevation, appearance of Q wave post infarct, T wave inversion
3. Lab
   - raised serum cardiac enzymes, troponin, creatine kinase MB, cardiac LDH

Question 13

Coronary intervention (3)

Answer 13

1. Thrombolysis - IV streptokinase
2. Angioplasty
3. Coronary artery bypass graft surgery