16.6 CVS Disease + Pregnancy

Question 1

A 27-year-old woman is 13 weeks pregnant. In the antenatal clinic, she is found to have an asymptomatic
heart murmur. A subsequent echocardiogram shows moderate to severe mitral stenosis.
a) List the causes of mitral stenosis. (15%)

Answer 1

> > Rheumatic fever
(commonest cause worldwide
but less common in
developed countries).

> > Infective endocarditis.

> > Degenerative calcification.

Question 2

b) How do the cardiovascular changes in pregnancy exacerbate the pathophysiology of mitral stenosis?
(45%)

Answer 2

1. > > 45% increase in intravascular volume: **
   the fixed output of the left atrium
   is unable to cope,

resulting in pulmonary oedema.

Increase in left atrial stretch predisposes
to atrial fibrillation and decompensation.

2. > > 20% increase in heart rate:
   shorter diastole so reduced time for flow
   across stenosed valve,
   reduces left ventricular filling,
   reduces cardiac output (CO).
3. > > Normal pregnancy has 40% increase
   in CO to cope with the 40%
   increase in oxygen consumption
   caused by the fetus and raised
   maternal metabolism.

This increase cannot be facilitated with a
significantly stenosed valve,
resulting in decreased exercise tolerance,
dyspnoea, cyanosis.

4. > > 20% reduction in systemic vascular resistance
   in pregnancy causes reduction in
   coronary artery perfusion,
   resulting in risk of ischaemia.

Question 3

c) Outline the specific management issues when she presents in established labour. (40%)

Answer 3

> > Decision regarding delivery mode
and location should have been made
antenatally
(tertiary centre with capabilities
of managing an urgent
valvotomy/valve replacement)
as she presented early in pregnancy.

> > Early communication between
senior anaesthetist, senior obstetrician,
cardiologist, cardiothoracic surgeon,
midwifery team.

> > Ensure cross-matched blood available
(she will tolerate volume loss
poorly and need replacement with
fluid that has oxygen-carrying capacity).

Vaginal

C section

Question 4

Vaginal MS delivery

Answer 4

> > Airway and respiratory:

• Supplementary oxygen.
• Oxygen saturations monitoring.
• Avoid nitrous oxide or hypoxia,
which could raise pulmonary vascular
resistance.

> > Cardiovascular:
• Intra-arterial blood pressure monitoring
(neuraxial analgesia-related hypotension
should be managed promptly with α-agonist).

• ECG monitoring (tachycardia and
loss of sinus rhythm are deleterious
to cardiac output).

• Monitor for blood loss.

• Cautious intravenous fluids if
dehydrated due to poor intake in labour
(maintain left atrial filling).

• Left lateral tilt to ensure unobstructed
venous return.

• Monitor for effects of autotransfusion after delivery.

> > Neurological:

• Early epidural to avoid sympathetically
mediated heart rate increases,
cautious top-ups to avoid drop in
systemic vascular resistance,
α-agonist use as necessary.

> > Pharmacology:
• Syntocinon to be given as an
infusion rather than as a bolus to avoid
tachycardia and vasodilatation.
Ergometrine contraindicated as will
cause pulmonary vasoconstriction.

> > Obstetric:
• Continuous fetal monitoring:
fetal distress may be an indicator of poor
maternal haemodynamics.

• Consideration of instrumental
second stage to avoid maternal effort as
the associated valsalva will reduce venous return.

Question 5

Mitral Stenosis and C section

Answer 5

Caesarean delivery:
» Airway and respiratory:
• Supplementary oxygen.
• Oxygen saturations monitoring.
• Avoid nitrous oxide or hypoxia, which could raise pulmonary vascular resistance.

> > Cardiovascular:
• Intra-arterial blood pressure monitoring –
reduced afterload must be
promptly managed with vasoconstrictor.

• ECG monitoring –
increased heart rate or loss of sinus rhythm is
deleterious to CO.

• Intravenous fluids to counteract
the effect of neuraxial block and to
maintain preload, but avoid left atrial overload.

• Replace blood with blood.

• Left lateral tilt to ensure unobstructed venous return.

• Monitor for the effects of
autotransfusion post delivery.

> > Neurological:
• Optimum mode of anaesthesia is
slow epidural top-up, combined
spinal and epidural with
low dose spinal component, or spinal catheter
to avoid sudden decrease in
systemic vascular resistance.

> > Pharmacology:
• If general anaesthesia is necessary,
ensure opioid at induction to
obtund the pressor response
and at a dose that obviates the need
for high-dose (vasodilatory) induction agent
(‘cardiac induction’).

Paediatricians to be alerted to this.

• Phenylephrine infusion to maintain
systemic vascular resistance
without inducing tachycardia.

• Avoid drugs that make tachycardia likely,
e.g. atropine.

• Short acting β-blockers if necessary.

• Syntocinon as an infusion to
avoid tachycardia and vasodilatation.

> > Obstetric:
• Early consideration of e.g.
B-lynch suture, intra-uterine balloon
or hysterectomy if excessive bleeding
as blood loss poorly
tolerated and pharmacological
options limited

(ergometrine causes pulmonary vasoconstriction
and hypertension,

prostaglandins cause bronchospasm
and may precipitate pulmonary oedema).