Page 38 - Medicine and Surgery

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34 Chapter 2: Cardiovascular system

termed foam cells, an accumulation of which causes a four patterns of plaque depending on its position and
visible pale bulge called a fatty streak. the ratio of the lipid pool to the fibrous cap:
Fatty streaks are often visible within the first year of life, Concentric fibrous: 48% of plaques
andtheseoccurworldwide,eveninareaswhereatheroma Eccentric fibrous: 12% of plaques
is uncommon. This suggests that the initiation of fatty Concentric lipid rich: 28% of plaques
streak may not be due to the risk factors for atheroscle- Eccentric lipid rich: 12% of plaques
rosis. The eccentric lipid rich plaques are the most likely
Stage III: The macrophages release lipid and cytokines to ulcerate due to the markedly abnormal flow pattern

into the intima, resulting in the stimulation of intimal through the vessel and the relatively thin fibrous cap.
cell proliferation. These cells secrete collagen and the
plaque becomes fibrotic. The result is a raised yellow
Microscopy
lipid plaque.
Plaquesarelocatedintheintimaofthearterialwall.They
Stage IV: The secreted collagen forms a dense fibrous

consist of a pale lipid rich area and a pink stained fibrous
cap. The lesion, now termed a fibrolipid plaque, con-
cap. They contain varying amounts of free lipid, collagen
tains free lipid as well as foam cells with an overlying
and foam cells. Late in the evolution of a plaque the
fragile endothelium.
underlying media becomes thinned by pressure atrophy.
Clinical features
The classical description of angina pectoris is of a heavy Investigations
chest pain, often described as like a tight band around The ECG is often normal, although there may be signs
the chest. It may range from a mild dull ache or mild of hypertrophy and old infarction.
chest tightness to a crushing, severe pain. It may radiate Exercise ECG can determine exercise tolerance and
to the jaw or arms (especially the left), sometimes it is usually shows ST depression or T wave changes in the
only in the jaw, neck, arm or hand. The nature of pain distribution of the lesion (see Fig. 2.4).
and its severity do not necessarily indicate the severity of Thallium-201 uptake scan may show areas of infarc-
disease. The pattern of pain is often more consistent. It is tion and reversible ischaemia.
brought on by exertion or emotion and relieved within Echocardiogram both during resting and under stress
afew minutes of rest. A grading system exists based on (dobutamine) may show abnormal ventricular wall
the level of activity provoking pain (see Table 2.4). It function.
is important to elicit whether there has recently been a Coronary angiography can be used but carries a small
reduction in the exercise tolerance (crescendo angina), morbidity and mortality risk.
or angina at rest (see section Acute Coronary Syndrome, MRI angiography is non-invasive and may prove a
page 36). useful alternative.

Macroscopy
Management
Atheroma tends to affect large and medium-sized arter-
Acute attack: stop exercise, use glyceryl trinitrate (GTN)
ies and is confined to the systemic circulation. There are
sublingually.
General management includes identification and
Table 2.4 New York Heart Association classification treatment of any exacerbating cause such as anaemia
of angina or thyrotoxicosis. Risk factor modification is crucial, in
particularstoppingsmoking,treatmentofhypertension,
Grade I Pain as a result of strenuous physical activity
only improving diabetic control and lowering cholesterol.
Grade II Slight limitation of ordinary physical activity Medical management: aspirin or other antiplatelet
(pain on walking up a hill) agents such as clopidogrel reduce the risk of myocar-
Grade III Marked limitation of ordinary activity (pain on dial infarction. HMGCoA reductase inhibitors (statins),
walking on the flat)
Grade IV Inability to carry on physical activity which lower cholesterol, are effective for primary
and secondary prevention of myocardial infarction.