Cardiovascular Journal of Africa: Vol 32 No 4 (JULY/AUGUST 2021)

CARDIOVASCULAR JOURNAL OF AFRICA • Volume 32, No 4, July/August 2021

230

AFRICA

The use of subcutaneous low-molecular weight heparin in

pregnant women with mechanical prosthetic valves without

meticulous anti-Xa monitoring is not an option and cannot

be emphasised enough. The administration of anticoagulants

and thrombolytic agents during pregnancy increases the risk of

sub-placental bleeding and embolism.

The index of suspicion for valve thrombosis must be high for

all pregnant women with mechanical heart valves. Patients may

present with worsening dyspnoea, palpitations or cardiac failure,

new murmurs, and new symptoms of cardiac or respiratory

compromise.

A detailed clinical examination and transthoracic

echocardiography (TTE) should be the basic assessment for all

pregnant women with mechanical prosthetic valves,

irrespective

of symptoms, as some may be asymptomatic, similar to our

second patient. TTE should be the imaging used as first line,

as a normal prosthetic heart valve function seen on TTE is

reassuring.

The echocardiographic signs of obstructive valve thrombosis

include reduced valve mobility, presence of thrombus, abnormal

trans-prosthetic flow, central prosthetic regurgitation, elevated

trans-prosthetic gradients, and reduced effective prosthetic area

(as seen in patient 2).

The 2017 guidelines from the American

Heart Association recommends urgent multimodality imaging

in patients with suspected mechanical heart valve thrombosis

to assess valvar function, leaflet motility and the presence and

extent of thrombus.

Surgery is considered in the presence of a thrombus.

CPB

surgery has implications for both the patient and her foetus.

Surgery carries a risk of up to 30% for foetal mortality. Over

the years, techniques have been introduced to decrease the risk

to the foetus, such as avoiding hypothermia during bypass,

maintenance of a high flow rate (> 2.5 l/min/m

), mean arterial

pressure > 70–75 mmHg,

maintenance of the haematocrit

above 28%, avoiding maternal hypoglycaemia and hypoxia,

as well as by placing the patient in the left lateral recumbent

position during CPB to avoid inferior vena cava compression by

the uterus.

15,16

Pulsatile flow has been suggested as being more beneficial in

pregnant women than in non-pregnant women as it decreases

vasoconstriction (in foetal lamb studies) by decreasing the

activation of the foetal renin–angiotensin–aldosterone axis,

which may reduce uterine contractions.

CPB can induce uterine

contractions, especially during the cooling and rewarming

phases.

In the above case series, the patients were assessed, managed

and counselled for valve-redo surgery, which was carried out

successfully. The implications for both the mother and foetus

were also discussed as surgical mortality rates are between five

and 36%.

Therefore, the prosthetic type, and imaging and

surgical risks (co-morbidities, age) are considered.

Follow up

is imperative after prosthetic heart valve-replacement surgery.

Conclusion

Women of reproductive age with prosthetic valves should

be counselled adequately for potential risks. Prosthetic valve

dysfunction in pregnancy increases the risk of adverse outcomes

for both mother and foetus. Therefore, careful management

is warranted to ensure positive outcomes and improvement in

quality of life.

Clinicians taking care of reproductive-age women should

enquire on a menstrual history and fertility desires. Patients

with medical or surgical disorders should be referred for

pre-pregnancy counselling and assessment. All women with

mechanical prosthetic cardiac valves should be counselled on

the various anticoagulant regimes available, with advantages

and disadvantages discussed in detail, preferably prior to

stopping contraception or planning a pregnancy. The options

should include oral anticoagulants, unfractionated heparin or

low-molecular weight heparin. Pregnant women with mitral

valve prostheses should have a detailed history/examination and

a TTE at the first antenatal consultation. The frequency of TTE

depends on symptoms and available resources.

These women should also be managed in a tertiary

institution. There should be a high index of suspicion for valve

dysfunction. Those with a suspicion of valve malfunction

should be urgently seen by a MDT consisting of cardiology/

cardiothoracic/high-risk obstetrics/neonatology (if relevant) and

anaesthetics. Patients requiring urgent valve-redo surgery should

be counselled extensively on the surgery and possible foetal and

maternal outcomes. Measures to decrease foetal loss at CPB

should be instituted in all pregnant women.

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