6.1 Pregnant Woman with Aortic Stenosis

Question 1

You are on-call on labour ward and are alerted of a pregnant
woman who had been admitted earlier that day with complaints of chest pain
and breathlessness.

She is 23-years-old in her first pregnancy at 32 weeks gestation.

She had been seen by the senior Obstetric registrar and has had blood
investigations, ECG, and an urgent ECHO.

The consultant Obstetrician is on her way from home.

Past medical history

She has a background of bicuspid aortic valve disease but had no cardiology
follow-up due to social reasons. She gets breathless on moderate exertion
and does only minimal household work.

obstetric history

She had seen the community midwife at 12 weeks and was then referred
for a consultant-led obstetric clinic due to the ‘heart condition’. The patient
failed to attend further antenatal follow-ups for the fear of being told to
terminate the pregnancy.

no significant past surgical
history.

on examination:
Looks unsettled and anxious
Heart rate: 95/min
Respiratory rate: 34/min
Blood Pressure: 80/60 mmHg

Blood tests
Hb 11.1 g/dL (13–16) Na 138 mmol/L (137–145)
WCC 3.0 × 109/L (4–11) K 4.8 mmol/L (3.6–5.0)
Platelets 242 × 109/L (140–400) Urea 2.5 mmol/L (1.7–8.3)
PCV 0.28 (0.38–0.56) Creat 42 umol/L (62–124)

ecHo report LA: dilated
LV: hypertrophied
RA: Normal size and function
RV: Normal size and function
Aortic valve: Thickened, possibility of a bicuspid valve cannot be excluded;
no calcification
Valve area: 0.8 cm2
Peak gradient: 75 mmHg
Mitral valve: Minimal mitral regurgitation
Tricuspid Valve/Pulmonary Valve: Normal
Systolic pulmonary artery pressure: 35 mmHg

summarise the case.

Answer 1

A high-risk primiparous pregnant woman in her third gestation,

admitted with signs of decompensation with a background
of underlying aortic valvular heart disease.

The problems are:
* Congenital bicuspid aortic valve with severe aortic stenosis with a high
gradient between the LV and aorta

• Signs of left ventricular hypertrophy with strain
• Pulmonary hypertension
• Poor social history and medical follow-up

Question 2

Describe the ECG.

Answer 2

Rate: 90
Rhythm: Regular sinus rhythm
Axis: Left axis

Intervals:
* PR—Normal
* QRS—Normal

Segments:
* ST Elevation lead V1–3
* ST Depression leads I, V5–6

Additional:
* Voltage criteria left ventricular hypertrophy
° R wave lead I + S wave lead III > 25 mm
° R wave V5 + S wave V1 > 45 mm
° T wave inversion V1–6

Interpretation:
* Voltage criteria for LVH
* Diffuse ST segment and T wave changes, indicating strain

Question 3

What findings can be diagnosed with a Doppler Echo in a patient with valvular heart disease?

Answer 3

1. Chambers—
   size and function,
   wall motion abnormalities,
   presence of thrombus
2. Septum—
   thickening or thinning, motion abnormalities
3. Valves—
   structural anatomy,
   thickening,
   number of cusps,
   calcification,
   stenosis, or regurgitation
4. Measurements—
   pressures in chambers,
   aorta and pulmonary vasculature,
   peak velocity across valves
   peak/mean gradients,
   ejection fraction

Question 4

How does a Doppler ECHO determine the gradient?

Answer 4

Gradient:
Doppler echocardiography takes advantage
of the acceleration of flow across a restrictive orifice
based on Doppler shift.

Blood flow velocities can be converted
to pressure gradients to yield mean and peak gradients
according to the Bernoulli equation.

The gradient is the difference in pressure
between the left ventricle and aorta in systole.

Question 5

How does a Doppler ECHO determine the valve area

Answer 5

Valve area: There are various ways to determine aortic valve area. The most
commonly used is the continuity equation.

By law of conservation of mass,

flow in one area
(i.e. left ventricular outflow tract, LVoT)

should be equal to the flow in the second area
(i.e. valve orifice)

provided there are no shunts between the two areas.

Flow is derived from the cross-sectional area and the velocity of flow.

Applying the law of conservation of mass:

Area of LVoT × Velocity in LVoT = Aortic Valve Area × Velocity at Valve

Aortic Valve Area (A2) = ALVoT (A1) × VLVoT (V1)
_____________________
V valve (V2)

Question 6

Is there any difference in the gradient values when measured using Doppler echocardiography and cardiac catheterisation techniques?

Answer 6

1. Doppler measurements overestimate the gradient,
   due to ‘pressure recovery’
   based on fluid mechanics theory.
2. Explanation: In fluid mechanics,
   flow equates to kinetic energy and
   pressure is potential energy.
3. According to the law of conservation of energy,
   the sum of kinetic and potential energy remains constant.
4. Kinetic energy (KE) + Potential energy (PE) = Constant

Question 7

Explain the changes in pressure across a valve

Answer 7

1. Proximal to stenosis:
   The blood flow in the left ventricle is
   such that there is a higher pressure and lower flow.
2. Stenosis:
   As the blood passes through the valve,
   there is an increase in KE and a decrease in PE.

This increased velocity of blood across the stenotic
valve accounts for a reduced pressure.

3.Post stenosis:
Distal to the orifice, the flow decelerates again.

KE is reconverted into PE
with a corresponding increase in static pressure.
This increased pressure immediately distal to the orifice
due to the reduction of
KE is called pressure recovery.

Doppler measures the highest velocity across the stenosis; hence, the
Doppler gradients are markedly greater, whereas catheterisation measures a
more or less recovered pressure at some distance from stenosis..

This pressure recovery depends on:
* Aortic valve area
* Ascending aortic area
* Transvalvular velocity

Question 8

What is aortic stenosis?

Answer 8

Aortic stenosis is a fixed output state,

where the narrowing of the aortic valve

impedes delivery of blood from the heart to the aorta.

Question 9

How can you classify aortic stenosis?

Answer 9

There are four grades of severity according to the valve area and the mean
gradient.

Grade of severity Valve area Mean gradient
Normal 3.0–4.0 cm2

Mild 1.2–1.8 cm2 12–25 mmHg

Moderate 0.8–1.2 cm2 25–40 mmHg

Severe 0.6–0.8 cm2 40–50 mmHg

Critical 0.6 cm2 > 50 mmHg

It should be remembered that classifying by gradient, rather than area, would
underestimate disease severity once the left ventricle starts to fail.

Question 10

What are the symptoms of aortic stenosis?

Answer 10

The classic triad of symptoms are:
* Angina
* Heart failure: dyspnoea, orthopnoea, paroxysmal nocturnal dyspnoea
* Syncope

Also associated with palpitations, hypertension, and oedema

Question 11

What are the signs of aortic stenosis?

Answer 11

1. • Slow-rising pulse of decreased amplitude (pulsus parvus et tardus)
2. • Hypertension
3. • Absent S2 or paradoxical splitting of S2 due to late closure of aortic valve
4. • Prominent S4 due to forceful atrial contraction against a hypertrophied
     ventricle
5. • Classic systolic murmur radiating to the carotids

Question 12

What does pregnancy do to maternal physiology that makes valvular diseases an important
concern?

Answer 12

Pregnancy is associated with significant haemodynamic changes such as:

• 30%–50% increase in stroke volume and cardiac output
• Increase in heart rate

Normal pregnancy is a volume overloaded state
where the valvular heart diseases
mainly severe stenotic lesions are not tolerated.

Also, the symptoms and signs that arise during the course
of normal pregnancy are similar to those reported by patients
with cardiac disease;

hence the difficulty in diagnosing deterioration.

Question 13

What are the causes of aortic stenosis?

Answer 13

• Congenital bicuspid aortic valve
• Rheumatic heart disease leading to mixed valve disease
• Degenerative calcific aortic stenosis

Question 14

Describe the pathophysiology
of aortic stenosis

Answer 14

1. Aortic Stenosis
2. Progressive decrease in the area of the aortic valve
3. Adaptation by hypertrophy

Early changes

1. Diastolic dysfunction
2. Decreased compliance
   Increased left ventricular diastolic pressure

Late changes

1. Systolic dysfunction
2. Myocardial ischaemia
   Myocardial fibrosis
   Abnormal wall motion

Above changes can lead to Afib + Mitral Regurg

Ultimately leads to
Decreased Contractility
+ Decreased Stroke Volume

Ending in heart failure

Right ventricular function is normally maintained even in severe cases.

Question 15

What other conditions are associated with congenital bicuspid valve?

Answer 15

It can occur with other congenital heart diseases
but mainly coarctation of
aorta (CoA) and VSD.

Question 16

What is the concern in COA?

Answer 16

Medial thickening and infolding of the
intimal tissue of the descending aorta
distal to the origin of the
left subclavian artery (juxta-ductal position).

Also associated with VSD are berry aneurysms
in brain and retina,
Turner’s syndrome,
other congenital abnormalities.

Question 17

What are the symptoms and signs of coA?

Answer 17

• Symptoms include
  headache,
  chest pain,
  fatigue and weak legs.
• Signs:
  ° Hypertension

° Prominent brachial and absent/weak femoral pulses

° Differential cyanosis

° Systolic or continuous murmur in the left infraclavicular and infrascapular areas

Question 18

What are the findings of COA on chest radiograph?

Answer 18

• Cardiomegaly due to LVH
• Signs of pulmonary oedema and failure
• ‘3’ sign (or inverted ‘3’ sign on barium studies)—
  coarctation with pre- and post-stenotic dilatation
• Rib notching of the fourth through eighth ribs due to presence of
  long-standing dilated intercostal collateral vessels

Question 19

What are the cardiac conditions where pregnancy is contraindicated?

Answer 19

Absolute
* Primary pulmonary hypertension
* Secondary pulmonary hypertension—Eisenmenger’s syndrome
* NYHA III/IV patients (New York Heart Association functional classification)

Relative
* Severe aortic and mitral stenosis
* Marfan’s syndrome with significant aortic root dilatation
* Prosthetic valves requiring anticoagulation
* Cyanotic heart diseases

Question 20

How can you risk stratify pregnant patients with cardiac diseases?

Answer 20

The WHo risk stratification seems an excellent model to predict pregnancy
outcome in patients with structural heart disease.

With an increasing level of risk score, more cardiac, obstetric, and neonatal complications were encountered.

A WHO score of 1 indicates low risk,
while a WHo score of 3 indicates a high risk and
a WHo score of 4 is a contraindication for pregnancy

Question 21

WHO classification

Answer 21

i: No detectable increased risk in maternal mortality (< 1%) and no/mild
increase in morbidity
* Uncomplicated PS, PDA, or mitral valve prolapse
* Successfully repaired simple lesions (ASD, VSD, TAPVD)

ii: Small increased risk of maternal mortality (5%–15%) and moderate
increase in morbidity
* Unoperated ASD or VSD
* Repaired TOF/COA
* Most arrhythmias
* Marfan’s syndrome without aortic dilatation

iii: Significantly increased risk of maternal mortality (25%–50%) or severe
morbidity

• Expert counseling required.
  If pregnancy is decided upon, intensive
  specialist, cardiac, and obstetric monitoring needed throughout
  pregnancy, childbirth, and puerperium.
  ° Mechanical valve
  ° Fontan circulation
  ° Unrepaired cyanotic heart disease
  ° other complex congenital heart diseases
  ° Marfan’s syndrome with aortic root dilatation 40–45 mm

iV: Extremely high risk of maternal mortality or severe morbidity
* Pregnancy contraindicated.
If pregnancy occurs, termination should
be discussed.
° Pulmonary arterial hypertension of any cause
° Severe systemic ventricular dysfunction (LVEF < 30%, NYHA class
III–IV)
° Severe symptomatic MS and AS
° Marfan’s syndrome with aortic root dilation > 45 mm
° Native severe CoA

Question 22

How would you manage this patient?

Preconception

Answer 22

Preconception

1. • European Society of Cardiology guidelines on ‘Management of
     Cardiovascular Disease During Pregnancy’
     recommends that patients with severe aortic stenosis should
     undergo intervention preconception if they are symptomatic
     and have ventricular dysfunction (EF < 50%).
2. • Careful cardiac exam and assessment of functional capacity to determine
     the likelihood of patients to tolerate the haemodynamic changes of
     pregnancy.
3. • Serial echocardiographic assessment to see disease progression.
4. • Patient education and lifestyle changes.
5. • Other investigations as needed.
6. • Medical treatment to optimise functional capacity.
7. • Aortic valve replacement (AVR) is the definitive treatment,
     and ideally this patient should have had an AVR preconception.

Question 23

How would you manage this patient?

Antepartum

Answer 23

• Joint care with cardiology, obstetrics, and anaesthesia in a tertiary care
  setup.
• Optimisation of medical therapy (discussed below).

Question 24

Intrapartum

Answer 24

1. • The timing and mode of delivery are discussed and are dictated by
     medical and obstetric condition;

vaginal delivery is indicated unless obstetric indication for caesarean delivery.

2. • Position:
     Avoid supine and lithotomy position as they are poorly tolerated.
     Nurse the patient in cardiac (legs lower than abdomen) or lateral position.
3. • Monitoring:
     Invasive arterial and central venous pressure monitoring
     in severe cases.

Pulmonary floatation catheter is used in patients with
severe and critical stenosis with symptoms of heart failure.

4. • Avoid pain and pushing:
     Sympathetic overactivity causes tachycardia,
     and the increased venous return with pushing causes decompensation.
     A short assisted second stage is recommended.
5. • Syntocinon is given as a diluted infusion.

6 * Auto transfusion is not tolerated; blood loss to some extent is beneficial
as long as venous return is maintained.

Question 25

Postpartum

Answer 25

1. • Monitoring is continued until 24–48 hours postpartum.
2. • Cardiology follow-up for a definitive management.

Question 26

Anaesthetic management

Answer 26

The goal is to maintain blood pressure and prevent maternal and foetal
distress, by maintaining
preload,
heart rate,
afterload.
Contractilty

BP = SV × HR × SVR

Question 27

Preload

Contractility

Answer 27

° Maintain preload by optimal positioning,
avoiding aortocaval compression,
adequate fluid balance.

° Vasodilatation with regional and general anaesthesia
can decrease the
venous return,
jeopardising the situation.

° Maintain contractility: General anaesthesia causes myocardial
depression whereas regional techniques do not.

Question 28

• Afterload

Answer 28

° Both general and regional anaesthesia decreases the afterload.

° As long as contractility is maintained,
a decrease in SVR is beneficial
as this would aid forward flow.

For this reason regional anaesthesia is
a good option as it does not have
any effect on cardiac contractility.

Question 29

• Heart rate

Answer 29

Slow/normal heart rate is maintained
and tachyarrhythmias are avoided.

° Tachycardia reduces the coronary perfusion
as diastolic time is reduced,

and also the preload is highly dependent
on the ‘atrial kick’
and arrhythmias obviate this factor.

Question 30

What is best + what is contraindicated

Answer 30

There is no absolute contraindication for any anaesthetic technique.

Understanding the pathophysiology aids management.

Traditionally GA was advocated for these patients.

It should be borne in mind that most anaesthetic agents cause vasodilatation

and it is the conduct of anaesthesia that is important rather than the specific technique.

The safe use of carefully titrated regional blocks using
epidural and spinal catheters is currently increasing.

Question 31

Key goals

Answer 31

1. • Slow/normal heart rate
2. • Adequate preload
3. • Preserve contractility
4. • Maintain afterload
5. • Treat anaemia and careful fluid management
6. • Prevent triggers that increase pulmonary vascular resistance—
     hypercarbia, hypoxia, acidosis, and pain
7. • Adequate invasive monitoring
8. • Transfer to tertiary care with progressive symptoms

Question 32

What medical management can you offer this patient?

Answer 32

The treatment options are limited.

There is no solid evidence that pathological course of
aortic stenosis is prevented with any medical therapy;

rather, it is symptomatic treatment that is considered to ‘buy time’.

There is equivocal evidence regarding the use of statins
in preventing disease progression.

1. Hypertension
2. Angina
3. Syncope
4. Pulmonary congestion

Question 33

Hypertension

Answer 33

• Vasodilators like ACE inhibitors and Angiotensin Receptor blockers
  (ARBs) are well tolerated in mild/moderate aortic stenosis.

They are used in severe aortic stenosis with extreme caution
to avoid critically reducing preload or systemic arterial blood pressure.

Be aware of the teratogenic effects of these drugs.

• β blockers:
  Used with caution in pulmonary oedema,
  the prevention of atrial fibrillation,
  prevention of aortic root dilation.

Question 34

2. Angina
3. Syncope

Answer 34

Angina
* Bed rest, oxygen

• β blockers to decrease myocardial oxygen consumption
• Nitrates to dilate coronary vessels
• Prevent reduction of preload and blood pressure

3. Syncope
   * If syncope is due to brady/tachy arrhythmias, then pacemaker or
   anti-arrhythmic drugs are used.

Question 35

Pulmonary congestion

Answer 35

• Digoxin
• Diuretics—
  used with utmost care because they can precipitate
  life-threatening haemodynamic compromise in patients
  who are preload dependent
• Careful titration of ACE inhibitors and ARBs

Question 36

What medical therapies would you instigate in this patient?

Answer 36

This patient is symptomatic with signs of heart failure.

• Cautious use of diuretics and nitrates to treat pulmonary congestion
• Ideally dealt with in tertiary hospital with expert help
• Invasive monitoring—
  ideally pulmonary artery pressure monitoring
• Careful fluid management

Further deterioration despite optimal medical treatment
warrants surgical intervention.

In cases where patients remain severely symptomatic
(in particular, if they have signs of heart failure),
aortic stenosis should be relieved before delivery.

This patient would benefit from a percutaneous balloon aortic valvuloplasty.

Question 37

What are the surgical interventions in severe aortic stenosis?

Answer 37

The surgical options are
* Percutaneous Balloon Aortic Valvuloplasty (PBAV)

• Aortic Valve Replacement (AVR)
• Transcatheter Aortic Valve Implantation (TAVI)

PBAV is ideal in this patient because it precludes the need for an open
bypass surgery in pregnancy and TAVI is done only in specialist centres.

Question 38

This patient then comes in with a successful pregnancy 3 years later having
had a mechanical prosthetic valve after her first pregnancy.

What is the risk of prosthetic
valve thrombosis in this patient?

Answer 38

Prosthetic valve thrombosis is a potentially devastating complication

Incidence of 0.7%–6% per patient per year.

The risk is higher in this patient because of:

1. • Presence of mechanical, rather than biological, prosthetic valve
2. • Hypercoagulable state of pregnancy
3. • Chance of interruption of anticoagulation in pregnancy

Question 39

How could her anticoagulation be managed during pregnancy?

Answer 39

Risk of valve thrombosis due to inadequate anticoagulation

is weighed against the

risk of direct harm due to the teratogenic drugs on the fetus.

Warfarin

Heparin - UFH / LMWH

Question 40

Warfarin

Answer 40

• Good for mother
• Bad for fetus as it crosses placenta and causes fetal embryopathy—
  nasal cartilage hypoplasia,
  brachydactyly,
  IUGR—

when administered between 6 and 12 weeks of gestation.

Question 41

Heparin – unfractionated (UFH) or low molecular weight heparin
(LMWH)

Answer 41

• Good for foetus
• Bad for mother due to increase in the risk of valve thrombosis.

Question 42

What is recommended with regards to anticoagulation and pregnancy

Answer 42

Three treatment choices according to the current recommendations are
suggested.

1. Treatment dose: subcutaneous UFH throughout pregnancy.
2. Treatment dose: subcutaneous LMWH throughout pregnancy.
3. UFH/LMWH until 13 weeks followed by warfarin.
   UFH/LMWH restarted at 36 weeks of gestation.

Monitoring anticoagulation with appropriate tests is important in pregnancy,
especially in high-risk patients with renal impairment.