Cardiovascular and respiratory pathology
Introduit| English | Sens |
|---|---|
| fatty streak | fatty streak |
| fibrous cap | fibrous cap |
| vulnerable plaque | vulnerable plaque |
| myocardial infarction | myocardial infarction |
| troponin/ˈtrɒpənɪn/ | A regulatory protein complex on thin muscle filaments that binds calcium and helps expose myosin-binding sites on actin. |
| obstructive disease | obstructive disease |
| restrictive disease | restrictive disease |
A plaque that was never big
- Many heart attacks start at a plaque that narrowed the artery by less than half. It was not the size that mattered; it was a thin cap that tore.
- Heart and lung disease is read from a sequence, a blood-test clock and one breathing ratio.
How a plaque grows
- LDL enters a damaged artery wall; macrophages eat it and become foam cells, forming a fatty streak 脂纹, the earliest lesion.
- Over years a fibrous cap 纤维帽 grows over a lipid core: a fibrolipid plaque. It narrows the artery and may cause angina on effort.
Rupture and thrombosis
- A vulnerable plaque 易损斑块 has a thin cap, a large lipid core and many inflammatory cells. When the cap tears, the core meets blood and a clot forms in minutes.
- A clot that blocks the artery causes a myocardial infarction 心肌梗死. A heavily calcified, thick-capped plaque rarely ruptures.
Put the plaque sequence in order.
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The earliest lesion is the fatty streak; rupture turns a stable plaque into an infarct.
Which plaque is most likely to rupture?
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Vulnerability depends on the cap and core, not the size.
The troponin clock
- Troponin 肌钙蛋白 leaks from dying heart muscle. It rises 3–4 hours after injury and stays raised for about 7–10 days.
- CK-MB rises and falls faster, over about 1–3 days, so a fresh rise after a few days points to a second infarct that troponin could not show.
Troponin can be raised for about a week after a heart attack.
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It stays raised for about 7–10 days, which is why CK-MB helps with a second event.
The infarct under the microscope
- Coagulative necrosis appears from 4–12 hours, neutrophils from 1–3 days, macrophages from 3–7 days, when the wall is softest and can rupture.
- Granulation tissue starts about 7–10 days, and a firm scar forms by about 2 months.
Match each finding to the infarct's age.
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Each phase has its own cells.
Spirometry: one ratio, two families
- FEV1 is the air blown out in one second; FVC is the total. Obstructive disease 阻塞性疾病 (asthma, COPD) traps air: FEV1/FVC below 0.70.
- Restrictive disease 限制性疾病 (lung fibrosis) shrinks both volumes, so the ratio stays normal or rises.
FEV1 is 2.1 L and FVC is 3.5 L. What is the FEV1/FVC ratio?
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2.1 ÷ 3.5 = 0.60, below 0.70, so obstructive.
Worked example: two spirometry results
- (Fictional lab) FEV1 1.6 L, FVC 4.0 L: ratio 1.6 ÷ 4.0 = 0.40, below 0.70. Obstructive, as in COPD.
- FEV1 1.8 L, FVC 2.0 L: ratio 0.90 with both volumes low. Restrictive, as in fibrosis.
FEV1 1.5 L, FVC 1.7 L, ratio 0.88, both volumes low. Which pattern is this?
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Both volumes shrink with a preserved ratio.
Worked example: dating an infarct
- (Fictional autopsy) The heart wall shows dead muscle full of neutrophils and no macrophages yet: about 1–3 days old.
- A heart that ruptured on day 5 matches the macrophage phase, when dead muscle is being cleared and the wall is weakest.
When is the heart wall most at risk of rupture after an infarct?
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Dead muscle is being removed before strong collagen has formed.
Three common slips
- Judging risk by plaque size. Thin-cap plaques rupture; thick calcified ones often do not.
- Using troponin for a second event within a week. It is still raised from the first; CK-MB clears sooner.
- Reading a low FEV1 alone as obstruction. Check the ratio; restriction lowers FEV1 too.
Recap
- LDL → foam cells (fatty streak) → fibrous cap plaque → rupture → thrombus → infarct.
- Troponin: rises 3–4 h, lasts 7–10 d. CK-MB: 1–3 d. Histology: neutrophils 1–3 d, macrophages 3–7 d, scar by about 2 months.
- FEV1/FVC below 0.70 = obstruction; both low with a normal ratio = restriction.