Cardiovascular Journal of Africa: Vol 29 No 5 (September/October 2018)

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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 29, No 5, September/October 2018 294 AFRICA
of valve thrombosis.25 Women at particularly high thrombosis
risk may be offered warfarin throughout pregnancy, except
at peripartum. Factors conferring higher risk of thrombosis
include older-generation mechanical heart valves, valves in the
mitral position, and previous history of thrombosis on heparin.
Improvements in prosthetic valve thrombogenicity over time
have reduced the risk of thrombosis.12
Among live births in the cohort, the rate of caesarean section
was 45%. While above the national average rate of 23.1%,26
it did not differ from the background rate for all high-risk
pregnancies receiving care at the tertiary hospital. HIV-positive
patients were more likely to have caesarean delivery (p = 0.0017),
perhaps reflecting the local policy of offering caesarean section
to HIV-infected mothers with persistent viraemia.
Eleven (38%) patients had episodes of arrhythmia, of which
seven (24%) had been documented prior to pregnancy, most
commonly atrial fibrillation. This rate is high relative to both the
developed5 and developing 9 world.
Nine (31%) pregnancies were complicated by worsening New
York Heart Association functional class, and three patients
developed pulmonary oedema. This compares unfavourably
with the cohort described by van Hagen et al.,5 where 7.5% of
pregnancies were complicated by heart failure, and may reflect
more advanced disease or the effects of co-morbidities present in
a low-resource setting.
Long hospital stays are costly and contribute negatively
to patient quality of life. Out-patient regimens such as self-
administered subcutaneous heparin as per newer guidelines22,27
could reduce length of admissions.
Pregnancy lossoccurred inninepregnancies (31%), comparable
with similar South African cohorts.9,13 Congenital abnormalities
were seen in three pregnancies (10%), however, only one (3.4%)
was considered to be due to warfarin embryopathy, a rate lower
than reported elsewhere.2,9,13
Warfarin embryopathy is caused by foetal exposure to
warfarin between six and 12 weeks’ gestation and is avoided by
using heparin during this period. Only two patients presented
prior to six weeks’ gestation, enabling timeous switching from
warfarin to heparin. Eleven patients presented between six and
12 weeks and received heparin from presentation to 12 weeks.
The patient whose foetus may have been affected by warfarin
embryopathy presented at 24 weeks’ gestation and therefore was
on warfarin throughout the vulnerable period.
Stengths and limitations
Comparison of this cohort with previously published literature
shows some differences in mortality rate and perinatal outcome,
which is likely spurious owing to the small sample size, and is
further skewed by the death related to complicated Takayasu’s
arteritis.
Conclusion
Pregnancies in patients on anticoagulation carry additional risks
due to both the underlying condition for which the patient is
anticoagulated and the anticoagulation itself. In this small study,
ischaemic events occurred intrapartum, while haemorrhagic
events occurred peri- or post-partum. Avoidance of post-partum
haemorrhage, particularly post-operatively, may be achieved
by a longer anticoagulation-free ‘window’ peripartum. More
studies are needed to identify the optimal window to balance
haemorrhagic and thrombotic risk but it is likely to be longer
than six hours. Heightened vigilance is required post-partum.
Contraception should be offered routinely at out-patient
cardiac clinics. Preconception counselling should emphasise
the importance of early presentation. Prolonged intravenous
heparin is likely to be a risk factor for infective endocarditis.
Subcutaneous out-patient LMWH should be considered.
The Hatter Institute for Cardiovascular Research is supported by the National
Research Foundation South Africa, the Medical Research Foundation South
Africa, the Maurice Hatter Foundation and SERVIER.
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