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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 27, No 2, March/April 2016
AFRICA
107
preload is excreted. Commonly, 48 to 72 hours after delivery,
the left ventricular preload may start to increase as the oedema
resolves.
46
This is an appropriate time to facilitate a diuresis.
The hypertension itself may persist for up to six weeks after
delivery, requiring management for this duration with diuretics
and second-line agents. Whereas angiotensin converting
enzyme (ACE) inhibitors are commonly used in non-pregnant
hypertensives, often calcium channel blockers are more rapidly
effective in these circumstances and are a good choice of
treatment for the limited period for which they will be required.
One of the most important aspects of managing the
postpartum pre-eclamptic is that of counselling. Pre-eclampsia
has been shown to be a marker of long-term risk. Specifically,
there is an association between hyperinsulinaemia, dyslipidaemia
and the risk of pre-eclampsia. These underlying metabolic
disorders are also risk factors for early onset vascular
disease (both coronary artery and cerebrovascular disease).
47
Consequently, women with early onset pre-eclampsia are at risk
of vascular arterial disease in later life. Attention therefore needs
to be paid to primary prevention of these conditions through
regular screening, and treatment for metabolic disorders. The
second long-term consequence of pre-eclampsia is that of an
increased risk of renal failure.
48
This risk correlates with the
number of pre-eclamptic pregnancies a woman may have and
indicates a need to pay attention to aspects of care in later life
that may have a renal protective effect, specifically the early and
adequate treatment of hypertension.
Chronic hypertension in pregnancy
Chronic hypertension during pregnancy may be divided into
two groups: uncomplicated chronic hypertension and chronic
hypertension with superimposed pre-eclampsia. The latter
group requires management according to the principles outlined
above, whereas the former requires out-patient care, often
with an altered approach to therapeutic intervention. Chronic
hypertension is defined as blood pressure of 140/90 mmHg or
more on two occasions before 20 weeks of gestation or persisting
beyond 12 weeks after delivery
Chronic hypertension with superimposed pre-eclampsia
The risk of developing superimposed pre-eclampsia is estimated
to be between 10 and 25%.
49
The possibility of decreasing this
risk merits consideration. The development of pre-eclampsia
cannot be averted by controlling blood pressure and there is no
therapy that has any major impact on the risk of developing
superimposed pre-eclampsia. However, there is some evidence
that the use of low-dose aspirin, given as a daily dose of 57 to 81
mg of aspirin, may reduce the risk of pre-eclampsia developing
in about 10% of women who are at risk of the disease.
50
It is not
clear why aspirin is effective, and initial theories related to altered
prostanoid metabolism have been discounted, with more recent
speculation focused on the possible interaction between aspirin
and the production of pro-inflammatory cytokines.
51
Aspirin
given in this dose is safe and has no effect on the foetus. Despite
the modest effect on the incidence of the disease, it remains
recommended therapy in women who are at risk.
The second strategy used to reduce the occurrence of
pre-eclampsia is based on the prophylactic administration of
large doses of oral calcium. Meta-analysis of the studies
conducted to date indicate that calcium administered in doses
of up to one gram three times a day may significantly reduce
the occurrence of pre-eclampsia and may also reduce the
development of severe hypertension.
52
The criticism of this data
arises from the observation that the two single largest studies in
the meta-analysis failed to reach statistical significance. Despite
these reservations, calcium supplementation is widely accepted
practice during pregnancy where there is a suspected risk of
pre-eclampsia.
Interventions that are not of benefit in preventing
pre-eclampsia include bedrest, the use of anti-oxidant vitamins
and antihypertensive therapy itself.
Given the imperfect prophylactic measures aimed at
preventing pre-eclampsia, care of pregnant women with chronic
hypertension requires appropriate precautions to ensure that
the development of superimposed disease is detected early
in its development because of the attendant risks of foetal
and maternal morbidity and mortality. Knowing who will
develop superimposed pre-eclampsia before it becomes clinically
manifest would be useful information.
The clinical phenotype of pre-eclampsia arises from changes
at the level of the foetoplacental unit and any early signs of
intra-uterine growth restriction or abnormal uterine artery
Doppler velocimetry may precede the onset of the clinical
disease.
49
The hallmark of superimposed pre-eclampsia is,
however, the development of proteinuria. The difficulty with this
is knowing when the proteinuria is a consequence of underlying
pre-eclampsia rather than due to renal disease caused by long-
standing hypertension or
a priori
renal disease with secondary
hypertension (in many communities HIV-associated nephritis
may be a major differential diagnosis).
This distinction may not be easily made on a clinical basis
and where a diagnosis of pre-eclampsia enters the differential
diagnosis, the patient deserves in-patient care and management
for presumptive pre-eclampsia until an alternative diagnosis
can be made. The natural history of pre-eclampsia sometimes
facilitates the distinction between pre-eclampsia and renal
disease as a cause for proteinuria because pre-eclampsia tends
to worsen as the pregnancy continues, whereas the chronically
hypertensive patient has an indolent condition that changes little
with the passage of time.
The recent interest in biomarkers may provide an alternative
way of diagnosing which hypertensive conditions have a placental
origin. Angiogenic and anti-angiogenic factors [placental growth
factor and the soluble receptor for vascular endothelial growth
factor (sFlt)] have been shown to be good predictors of placental
disease and may provide a ready means of discriminating
between various types of hypertensive disease in pregnancy,
specifically identifying those most at risk of adverse outcome.
53
Uncomplicated chronic hypertension
Uncomplicated chronic hypertension does not usually affect the
pregnancy outcome to any significant degree. The drugs used to
treat hypertension outside pregnancy may need to be revised and
alternatives introduced in order to protect the foetus.
Physiological changes during pregnancy have an impact on
chronically hypertensive women as well. Specifically, they will
vasodilate during the second trimester, leading to a fall in blood