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Chapter 2: Clinical 25

perfusion is dependent on the heart rate, the arterial cases the pain causes the patient to limp, hence the term
blood pressure as well as the resistance of the whole vas- claudication and the pain characteristically disappears
culature. Changes in any of these may result in syncope. when exertion is stopped, hence the term intermittent.
There may be no warning, or patients may describe feel- The distance a patient can usually walk on the flat be-
ing faint, cold and clammy prior to the onset. They may fore onset of pain is termed the claudication distance.
have blurred vision, tinnitus and appear very pale prior Intermittent claudication is caused by peripheral vascu-
to the loss of consciousness. Whilst unconscious they lar insufficiency to the muscles of the legs. The disease is
are hypotonic with a very slow or difficult to feel pulse. in proximal large and medium-sized arteries to the lower
Within a few seconds they spontaneously recover, they limbs,i.e.theiliacandfemoralarteries.Asthenarrowing
tend to be flushed and sweaty but not confused (unless ofthearteriesbecomesmoresignificant,theclaudication
prolonged hypoxia leads to a tonic-clonic seizure). distance decreases. Eventually rest pain may occur, this
Vasovagal syncope is very common and occurs in the often precedes ischaemia and gangrene of the affected

absence of cardiac pathology. Predisposing factors in- limb.
clude prolonged standing, fear, venesection, micturi-
tionorpain.Thereisperipheralvasodilationcausinga Signs
reduced ventricular filling. The heart contracts force-
fully, which may lead to a reflex bradycardia via vagal Oedema
stimulation and hence a loss of consciousness.
Postural syncope (fainting on standing) is seen in pa- Oedema is defined as an abnormal accumulation of fluid

tients with autonomic disorders, salt and water deple- within the interstitial spaces. A number of mechanisms
tion, hypovolaemia or due to certain drugs especially arethoughttobeinvolvedinthedevelopmentofoedema.
antianginal and antihypertensive medication. Normally tissue fluid is formed by a balance of hydro-
Cardiac arrhythmias may result in syncope if there is a static and osmotic pressure.

sudden reduction of the cardiac output. This may oc- Hydrostatic pressure is the pressure within the blood
cur in bradycardias or tachycardias (inadequate ven- vessel (high in arteries, low in veins). Oncotic pressure is
tricular filling time). The loss of consciousness occurs produced by the large molecules within the blood (albu-
irrespective of the patient’s posture. A Stokes–Adams min, haemoglobin) and draws water osmotically back
attack is a loss of consciousness related to a sudden into the vessel. The hydrostatic pressure is high at the
loss of ventricular contraction particularly seen dur- arterial end of a capillary bed hence fluid is forced out of
ing the progression from second to third degree heart the vasculature (see Fig. 2.1).
block. The colloid osmotic pressure then draws fluid back in
Carotid sinus syncope is a rare condition mainly seen at the venous end of the capillary bed as the hydrostatic

in the elderly. As a result of hypersensitivity of the
carotid sinus, light pressure, such as that exerted by
atight collar, causes a severe reflex bradycardia and
hence syncope.
Net fluid Net fluid
Exertional syncope occurs in aortic valve or subvalve

movement movement
stenosis. The syncope results from an inability of the
heart to increase cardiac output in response to in- Hydrostatic Oncotic
creased demand. 0ncotic Hydrostatic
pressure
pressure
The immediate management of syncope or impending Capillary
syncope is to lie the patient down and raise their legs
increasing cerebral blood flow.
Intermittent claudication
Artery Vein
Claudication describes a cramp-like pain felt in one or
both calves, thighs or buttocks on exertion. In severe Figure 2.1 Mechanism of oedema.