Step 8 of 9

Congenital heart diseases and pregnancy

Currently, 0.1% of births involve parturients with symptomatic congenital heart disease [22]. Mortality among these women is 22 times higher and incidence of cardiovascular complications is 10 times higher than among non-sufferers (OR 22.1 and 10.54, respectively) [22]. Mean maternal mortality is 4.8%, but this varies considerably by pathology: from < 1% in well-tolerated heart diseases to 38% in cases of severe pulmonary hypertension (PAH) or severe cyanosis (SaO2 < 85%) [1]. Death often occurs within several days of delivery. The incidence of cardiovascular complications during pregnancy varies between 11% and 33% (mean 12%): cardiac decompensation, cyanosis, PAH crisis, thromboembolism, stroke, arrhythmia, endocarditis [6,11,20]. The incidence of obstetrical complications is approximately 30% [6,22]. Cyanosis present prior to pregnancy has a negative impact on prognosis, since the morbimortality rate is 15% among non-cyanotic women, but may exceed 50% if cyanosis is severe [6]. 

Approximately 28% of neonates suffer from major problems: premature birth, low birth weight, foetal death or perinatal death [11]. Mean infant mortality is 4%, rising to 40-65% in severe cyanotic heart diseases and Eisenmenger’s syndrome (fixed pulmonary hypertension) proportionate to the mother’s degree of hypoxia [6,7,18]. The mean incidence of premature birth is 16-20%, which is over four times higher than the normal incidence in western countries. In severe pathologies, premature birth occurs in 22-65% of cases [4,6]. Foetal complications (premature birth, low birth weight, miscarriage and death) are proportionate to the mother’s low uterine blood flow and cyanosis – if the mother’s SaO2 is > 90%, the foetal survival rate is 92%, but if SaO2 is < 85%, it is only 12% [12,18]. 

The main independent factors determining prognosis reflect the severity of the pathology [5,7,18].
 
  • History of cardiac events or major arrhythmia;
  • NYHA class III-IV functional failure;
  • Cyanosis and hypoxia (SaO2 ≤ 90% at rest, Hb > 150 g/L before pregnancy);
  • Pulmonary hypertension (mean PAP > 35 mmHg);
  • Systemic ventricle dysfunction, subaortic RV;
  • Severe obstruction of the left ejection pathway. 
A therapeutic abortion is therefore indicated in early pregnancy in the event of severe PAH and cyanosis (Table 15.12) [21]. The mean incidence of genetic transmission of the same disease as one of the parents to the offspring is 2-4%. However, this rises to 8% in cases of VSD, 15% for aortic stenosis, and 50% for Marfan syndrome [23]. Progesterone-based pills should be used as contraception, since oestrogen entails an excessive risk of thromboembolism [2,3,23]. 

Pregnancy causes significant haemodynamic modifications: circulating blood volume increases (+ 50%), SVR falls, cardiac output and heart rate increase (+ 30-40%) (see Chapter 22, Maternal haemodynamics). Although this situation considerably affects congenital heart disease patients, its risk is variable depending on the pathology (Table 15.13). A non-cyanotic L-to-R shunt is generally well tolerated provided that left ventricular function is preserved and pulmonary pressure continues to be normal. However, major L-to-R shunting may decompensate the LV and be combined with pulmonary arterial hypertension (PAH). In such cases, the degree of PAH largely determines the prognosis [16]. Cyanotic R-to-L shunting is increased by the stress of labour and childbirth since PVR increases due to the effects of sympathetic discharge. In the event of PAH, PVR is fixed and does not fall with arterial vasodilation associated with pregnancy. The shunt’s R-to-L component increases and the patient becomes cyanotic. Maternal mortality in the event of PAH is 30-70% depending on the pathology [24]. It often occurs within several days of delivery [17]. In lesions where cardiac output is reduced by ejection stenosis as observed in coarctation of the aorta, the increase in cardiac output associated with pregnancy is only possible through an increase in heart rate, since it is not possible for the stroke volume to rise. Bradycardia should be avoided in these patients [14].


Unless the ascending aorta dilates, in which case a caesarean section is required, vaginal delivery is possible for most congenital heart disease patients. However, the decision is dependent on the pathology and any foetal distress. In a general sense, the active phase of labour is potentially dangerous with its Valsalva manoeuvres and autotransfusions at each contraction. Labour should ideally be accelerated by forceps or ventouse. Epidural analgesia is essential for limiting catecholamine release and ensuring haemodynamic stability, provided that sympathetic blockade is installed gradually. By adding an opiate, it is possible to enhance the analgesic effect and limit circulatory disruptions in comparison to a local anaesthetic alone. It is prudent not to add epinephrin. In contrast, spinal anaesthesia causes systemic vascular resistance to drop suddenly and abruptly reduces preload, which is poorly tolerated in situations in which systemic arterial vasodilation exacerbates the pathology, as in cases of R-to-L shunting and bidirectional shunting with pulmonary arterial hypertension or pulmonary stenosis. However, it is recommended in situations in which SVR must be reduced such as L-to-R shunts (ASD, VSD, patent ductus arteriosus, etc.) [8,10]. If skilfully manipulated, a spinal-epidural combination is conceivable if SVR is appropriately maintained [8]. In the event of PAH or situations in which it is advisable to reduce PVR, general anaesthesia with hyperventilation and nebulisation of vasodilators by inhalation is beneficial. However, the results of epidural anaesthesia with very gradually installed sympathetic blockade are excellent, provided that RV preload and SVR are appropriately maintained [8,13].

SpO2 indicates the degree of R-to-L shunting. An arterial catheter and central venous line (CVP) are useful for adjusting the vasopressors and blood volume required for maintaining uterine perfusion pressure and balancing a R-to-L shunt or potential right-sided failure in the event of pulmonary hypertension. In cyanotic mothers, O2 delivery and SVR must be sufficient to ensure the highest possible SaO2. Preload may vary considerably during delivery: it increases suddenly by maternal autotransfusion at each uterine contraction and decreases dangerously in the event of haemorrhage. These variations are poorly tolerated in congenital heart disease patients for several reasons: stenosis limits blood flow, ventricular dysfunction prevents adaptation to blood volume variations, shunting diverts part of the circulating volume from the systemic circulation, pulmonary hypertension maintains fixed and low pulmonary blood flow. Hypovolaemia therefore manifests as arterial oxygen desaturation.

While pregnancy and labour generally run smoothly in patients with class I and II diseases (Table 15.13), it is essential that those with severe pathologies (class > II) are followed up at specialised centres, which offer all the necessary expertise in obstetrics, anaesthesia and congenital cardiology [2,4,8,18].

Anaesthesia for the main diseases

Recommendations may be summarised briefly (see Table 15.10) (for further detail, see Chapter 22 Congenital heart diseases) [10,14,17].
 
  • ASD, VSD and any simple L-to-R shunt: avoid any increase in PVR – pregnancy-induced vasodilation is favourable for these patients. Neuraxial blockade (epidural and intrathecal) recommended for vaginal delivery and caesarean section – general anaesthesia possible for caesarean section.
  • Tetralogy of Fallot, R-to-L shunting: the fall in SVR and labour exacerbate cyanosis and cause foetal hypoxaemia. In the event of hypovolaemia, the shunt's R-to-L component increases as it does when systemic pressure falls. General anaesthesia is the preferred option – halogenated agent with esmolol and phenylephrine in the event of hypoxic crisis. An epidural is possible with very gradual installation of sympathetic blockade and maintenance of RV preload and SVR. Spinal anaesthesia is not recommended (excessive drop in SVR). In the event of a hypoxic crisis, esmolol is administered to reduce dynamic stenosis of the RVOT and phenylephrine or norepinephrin to increase pulmonary blood flow through the VSD and collaterals.
  • Palliative or corrective shunt (Blalock-Taussig, Waterston): avoid reducing SVR as it determines pulmonary blood flow. General anaesthesia recommended – an epidural is possible if sympathetic blockade is installed very gradually and sympatholysis is minimal.
  • Eisenmenger’s syndrome (fixed PAH): pulmonary blood flow is fixed and cannot keep pace with increased O2 requirement. The increase in circulating volume further increases PAP. The fall in SVR exacerbates cyanosis (increase in the shunt’s R-to-L component). Epidural with gradual installation of sympathetic blockade in order to avoid a reduction in SVR is generally preferred to general anaesthesia whose results were inferior in several studies [15]. Spinal anaesthesia is not recommended [19]. Nevertheless, general anaesthesia enables hyperventilation (PVR reduced by hypocapnia) and administration of pulmonary vasodilators by inhalation (NO, prostaglandins). Since the RV is hypertrophied due to high PAP, the increase in afterload due to positive pressure ventilation is negligible. Anything that increases PVR must be avoided (hypoxaemia, hypercapnia, pain, acidosis, hypothermia, N2O, desflurane) and SVR must be kept high (norepinephrin). Oxytocin increases PVR and reduces SVR. Like all uterotonic agents, it must be administered extremely cautiously (infusion < 2 IU/min) and never as a bolus [19].
  • Fontan circulation: this type of circulation struggles to adapt to the haemodynamic demands of pregnancy. The incidence of maternal complications is 10% and that of miscarriages is 30-50% [7,8]. CVP must remain high (high preload, blood volume maintained). Intrathoracic pressure must remain low. Regional anaesthesia is clearly preferable to general anaesthesia (spontaneous breathing). Due to the risk of thrombosis, patients are generally anticoagulated. Any increase in PVR must be avoided – prostaglandin analogues are contraindicated and oxytocin must only be administered as a very slow infusion.
  • Coarctation of the aorta: maintain tachycardia and vascular resistance (high SVR). General anaesthesia recommended for caesarean section. Epidural anaesthesia may be possible for vaginal delivery. Spinal anaesthesia is contraindicated as it lowers SVR. A post-ductal catheter should be used to monitor arterial pressure distal to the coarctation as this determines pressure in the uteroplacental vascular system.
  • Bicuspid aortic valve and aortic aneurysm (Marfan syndrome): the hypertensive crisis caused by labour entails a significant risk of rupture or dissection. Vaginal delivery under epidural and accelerated labour is possible if the diameter of the aorta is < 40 mm (Marfan) or < 45 mm (bicuspid aortic valve). If dilation of the ascending aorta is greater than these figures or has increased during pregnancy, a caesarean section under GA is recommended in order to stabilise arterial pressure [9]. 
     
 
Congenital heart diseases and pregnancy
Factors of poor prognosis:
    - History of cardiac events or major arrhythmia;
    - NYHA functional class of III-IV
    - Hypoxia and cyanosis: SaO2 ≤ 85% at rest, Hb > 150 g/L 
    - Pulmonary hypertension: mean PAP > 35 mmHg
    - Ventricular dysfunction, systemic RV
    - Severe ejection obstruction

Preferred anaesthesia during labour:
    - L-to-R shunt: neuraxial blockade (spinal anaesthesia or epidural)
    - R-to-L shunt: general anaesthesia, epidural* with very gradual sympathetic blockade + vasoconstrictor
    - L-to-R palliative shunt: general anaesthesia, epidural* with gradual sympathetic blockade + vasoconstrictor
    - PAH: general anaesthesia with hyperventilation, epidural* with gradual sympathetic blockade + vasoconstrictor
    - Aortic stenosis, coarctation: general anaesthesia, epidural* with gradual sympathetic blockade + vasoconstrictor
    - Fontan circulation: spontaneous respiration, neuraxial blockade + maintain preload
    - Dilation of the aorta + AI: caesarean section under GA
    - Maintain sufficient preload
    - *: spinal anaesthesia not recommended


© BETTEX D, CHASSOT PG, January 2008, last update February 2020

 

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15. Anesthesia for adult congenital heart disease patients