FRCA Notes

Pulmonary Hypertension in Obstetrics

This page should be viewed in tandem with the page on pulmonary hypertension in the general adult population.

Resources

  • Pulmonary hypertension is a high-risk, high-mortality disease state
  • It is a WHO class IV maternal risk cardiac disease i.e. pregnancy should be avoided
  • It accounts for 1% of cardiac disease in pregnancy

Maternal risks Foetal/neonatal risks
Major cardiac events Prematurity
↑ risk of VTE Stillbirth
↑ PET IUGR
↑ PPH
Mortality Mortality up to 30%
  • The risk of complications varies between individuals, but in general is higher with greater pulmonary artery pressures (particularly >70mmHg)
  • Mortality tends to be from right heart failure owing to an inability to cope with the physiological changes of pregnancy
  • Mortality in parturients with pulmonary hypertension is decreasing with better therapies and MDT management, but still may be as high as 33%

Pulmonary hypertension

  • A blend of processes contribute to increasing PVR:
    1. Sustained pulmonary vasoconstriction
    2. Cellular proliferation in the vessel walls
    3. Localised thrombi formation

  • Said vascular remodelling exhausts endogenous vasodilators (nitric oxide, prostacyclins) and up-regulates vasoconstrictors (endothelin 1)
  • There is consequent increases in RV afterload, abnormal ventricular remodelling and eventually RV dysfunction/failure, which is the primary determinant of survival in PAH.

Pregnancy and PAH

  • Normally, the increased progesterone levels of pregnancy lead to pulmonary vasodilation & recruitment of non-perfused arterioles
  • However, in pulmonary hypertension the thickened and vasoconstricted pulmonary arteries are unable to accommodate the increased cardiac output & plasma volume of pregnancy
  • This leads to increased PVR, further RV strain and higher risk of RV ischaemia/failure
  • There may be consequential LV failure due to septal bowing and interventricular interdependence
  • The most hazardous period ante-partum is 20-30 weeks' gestation i.e. peak cardiac output

  • Further risk arises during labour, with raised PVR and altered RV preload due to:
    • Sympathetic stimulation from pain
    • Fluid shifts including autotransfusion from the placenta at delivery
    • Raised intrathoracic pressure from Valsalva

  • Risks persist up to 6 months post-partum including due to the risk of VTE adding to pulmonary arterial microthrombi load

  • Most patients will have an ante-natal diagnosis, but patients may present in pregnancy with features of right heart failure

Symptoms

  • Exertional dyspnoea
  • Fatigue
  • Syncope
  • Chest pain
  • Dry cough
  • Peripheral oedema

Signs

  • Tachycardia
  • Raised JVP
  • Hepatomegaly
  • Ascites
  • Mottled and/or cool peripheries
  • Hypoxia
  • Murmurs (if valvular pathology)

Investigations

  • ECG
    • P-pulmonale
    • RV strain or hypertrophy
    • RAD
    • RBBB
    • Prolongation of the QRS and/or QTc in severe disease

  • TTE is the first line
  • PA catheter remains the gold standard

  • ToP is recommended
  • MDT management in a specialist centre e.g. maternal–fetal medicine (MFM) obstetricians, cardiologists, obstetric anaesthetists and midwives
  • May need input from ICM (± ECMO), haematology, cardiothoracics and neonatologists too
  • Regular reviews (1-2x/month) and prompt investigation of deterioration in functional capacity, as this is the best prognostic indicator

Therapies

  • PDE-V inhibitors are first-line therapy e.g. sildenafil
  • Prostacyclin analogues are also suitable in pregnancy
    • They may increase bleeding risk and cause thrombocytopaenia, although there aren't reports of neuraxial haematoma

  • Endothelin-1 receptor analogues (e.g. bosentan) are contraindicated in pregnancy
  • Riociguat (a cGMP stimulator) is contraindicated

  • Anticoagulation will need to be managed; those on warfarin or DOACs may require transition to LMWH
  • Avoid fluid overload with reduced oral intake of water and salt, although diuretics may be used (furosemide; spironolactone is contra-indicated)
  • Correction of iron deficiency, which is common in those with pulmonary hypertension in pregnancy

Mode of delivery

  • Timing of delivery is balance between maternal and neonatal risks; 34 weeks is recommended but will be individualised
  • Location of delivery will depend on local resources

  • LSCS is the recommended mode of delivery to avoid the physiological strain of labour, although this is only by consensus guideline
  • Vaginal delivery may be suitable, especially in the multiparous patient
  • Vaginal delivery benefits from reduced infection, haemorrhage and VTE risk

Haemodynamic management

  • Goals include:
    • Avoid rises in PVR and RV afterload e.g. by avoiding hypoxia, hypercapnoea, acidosis, pain or high airway pressures
    • Maintain SVR

  • This is acheived by:
    • Continuation of existing pulmonary vasodilator therapy e.g. PDE-5 inhibitors, prostacyclin
    • Careful fluid balance monitoring inc. concentrating drugs where possible
    • Supplementary oxygen
    • Positive inotropic support e.g. dobutamine, milrinone, adrenaline
    • Vasopressors to counteract vasodilation from neuraxial intervention e.g. noradrenaline, vasopressin (NB phenylephrine is contraindicated)

Analgesia and anaesthesia

  • Regional technique with a carefully titrated lumbar epidural is the recommended method of labour analgesia
  • Neither entonox nor opioid analgesia is recommended as they can precipitate hypoxia, hypercapnoea and/or increase PVR

  • Either epidural top-up or CSE technique is preferable for operative delivery
    • The authors of the above-linked BJA article use 1ml 0.5% heavy marcaine (5mg) + fentanyl + morphine followed by incremental epidural top-up
  • A single-shot spinal is contraindicated owing to the propensity for rapid haemodynamic changes which can compromise RV function
  • GA may be required (e.g. anticoagulation contraindicates neuraxial technique, patient unable to lie flat)
    • It carries high risk and is reported to carry a 4x increased mortality vs. RA

Monitoring

  • AAGBI as standard
  • Arterial line
  • CVC
  • ± PA catheter, which is not routinely recommended but may be beneficial in individual cases

Uterotonics

  • Oxytocin boluses should be avoided, or only very small boluses (0.1 IU) used
  • Oxytocin should preferntially be diluted and infused

  • Carboprost and ergometrine should both be avoided
  • Misoprostol is considered safe, but is less effective

Pulmonary hypertensive crisis

  • Most likely to present post-partum, but can occur at any time
  • Presents with features of acute right heart failure
  • Management involves:
    • Correction of underlying abnormal physiological factors which are contributing e.g. hypoxia, hypercapnoea etc.
    • Pulmonary vasodilatory therapy e.g. prostacyclins
    • Positive inotropy e.g. dobutamine, milrinone
    • Vasopressor to support RV perfusion
    • Reduced RV afterload e.g. diuretics

  • Highest risk period is post-partum; mortality is highest in the first month after delivery
  • Monitor in an HDU setting for 24-48hrs
  • Ensure adequate thromboprophylaxis as at high risk of VTE
  • Offer contraception to avoid future pregnancy