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88 Chapter 2: Cardiovascular system

the legs and increases systemic vascular resistance. This
reduces the right to left intracardiac shunt and provides
some symptomatic relief. On examination cyanosis and
clubbing may be present. There is a right ventricular
heave. On auscultation there is initially a long systolic
murmur across the pulmonary valve, which shortens as
cyanosis develops.
Spasm of the infundibular muscle in the right ven-
tricular outflow tract results in further compromises the
right cardiac outflow causing worsening cyanosis and
often loss of consciousness. These are termed hyper-
cyanotic or tet spells.

Investigations
Figure 2.20 Tetralogy of Fallot.
ChestX-rayoftenshowsaheartofnormalsizebuttheleft
heartborderisconcave(bootshape)duetothesmallpul-
Right ventricular outflow obstruction (pulmonary

monary trunk. There is normally pulmonary oligaemia
stenosis).
due to low pulmonary blood flow. ECG shows right axis
Right ventricular hypertrophy.

deviation and right ventricular hypertrophy. Echocar-
diogram is diagnostic.
Aetiology
Embryological hypoplasia of the conus, which gives rise
tothemembranousventricularseptum.OccursinDown Management
syndrome and as part of fetal alcohol syndrome. Symptomatic infants may require a Blalock–Taussig
shunt,usingatubeofGortextoconnectthesubclavian
Pathophysiology artery to the pulmonary artery. This provides a left to
The pulmonary stenosis results in high right ventricular rightshunt replacing the duct as it closes.
pressure and hence right ventricular hypertrophy. The Surgical correction is performed at 4–6 months under
large VSD and high right heart pressures cause a right cardiopulmonary bypass. It is performed by opening
to left shunt. The aorta is over the shunt as the VSD is the pulmonary stenosis (by patch enlargement where
high and thus there is also flow from the right ventricle indicated) and closure of the VSD.
directly into the aorta. The degree of pulmonary stenosis
isvariable(rangingfrommildtoatresia),thustheclinical
picture ranges in severity. The right ventricular outflow Cardiovascular oncology
tract obstruction is often progressive.

Clinical features Atrial myxoma
In rare severe cases cyanosis develops within days as the
Definition
pulmonary circulation is dependent on a patent ductus
An atrial myxoma is a benign primary tumour of the
arteriosus. More commonly presentation is later with
heart most commonly arising in the left atrium.
progressive cyanosis over a few weeks. Initially it may
only be present on exertion, but as the right ventricu-
lar outflow obstruction is progressive cyanosis becomes Incidence
evident at rest, and the characteristic squatting position Primarytumoursoftheheartarerare,butatrialmyxoma
may be adopted. Squatting traps unsaturated blood in is the most common.