Heart disease in preganancy

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"heart disease" AND "pregnancy" AND management

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Heart Disease in Pregnancy

Heart disease is the most common cause of indirect maternal mortality, complicating 1-4% of all pregnancies. Rates are rising due to advanced maternal age, obesity, hypertension, and diabetes. The predominant aetiology is congenital heart disease in developed countries and rheumatic heart disease in developing countries.

1. Haemodynamic Changes of Normal Pregnancy

Understanding these changes is essential because they stress an already-compromised heart:

Parameter	Change
Blood volume	+50% by week 30
Cardiac output	+30-45% by week 20
Heart rate	+10-20 bpm
Systemic vascular resistance	Decreased (oestrogen-mediated arteriolar dilation)
Blood pressure	Unchanged (increased volume offset by low SVR)

Stroke volume is the dominant factor early in pregnancy; heart rate increase predominates later.
The enlarged uterus compresses the inferior vena cava in late pregnancy, reducing venous return - this is why lateral decubitus positioning is preferred in labour.
Plasma volume rises more than red cell mass, creating physiological anaemia (Hb ~11 g/dL, Hct ~33%).
During labour and delivery: uterine contractions cause wide swings in venous return; placental separation causes autotransfusion of ~500 mL - both can precipitate pulmonary oedema in diseased hearts.

Source: Creasy & Resnik's Maternal-Fetal Medicine, p. 1244; Fuster and Hurst's The Heart, 15th ed.

2. Diagnosis - Distinguishing Normal from Pathological

Normal pregnancy produces many findings that can mimic heart disease:

Normal/Physiological findings:

Systolic murmurs (>95% of pregnant women)
Mammary flow murmurs, venous hums
S3 gallop (sometimes)
Dependent oedema, mild cardiomegaly on X-ray
Dyspnoea, easy fatiguability, dizzy spells, even syncope

Red flags indicating true cardiac disease:

Severe dyspnoea, syncope with exertion, haemoptysis
Paroxysmal nocturnal dyspnoea, chest pain on exertion
S4 gallop, cyanosis, clubbing
Diastolic murmurs
Sustained cardiac arrhythmias
Loud, harsh systolic murmurs

ECG changes in normal pregnancy: Left axis shift (elevated diaphragm), non-specific ST/T-wave changes (usually lead III). These must not be over-interpreted.

Echocardiography is safe; radiation-based imaging (radionuclide, CT, angiography) should be avoided unless essential.

Source: Creasy & Resnik's Maternal-Fetal Medicine, p. 1243-1244

3. Risk Stratification

Modified WHO (mWHO) Classification

This is the primary, easiest-to-use risk tool:

mWHO Class	Risk	Examples
I	No/negligible increased risk	Uncomplicated small ASD/VSD, mild PS, repaired simple CHD, isolated ectopics
II	Mildly increased risk	Unoperated ASD/VSD, repaired ToF, most arrhythmias
II-III	Moderate risk	Mild LV impairment, hypertrophic cardiomyopathy, Marfan without aortic dilatation
III	Significantly increased risk; specialist care mandatory	Moderate LV impairment, mechanical valves, systemic RV, Fontan (uncomplicated)
IV	Extremely high risk; pregnancy contraindicated	PAH, severe systemic ventricular dysfunction (EF <30% or NYHA III-IV), previous PPCM with residual LV impairment, severe symptomatic AS, severe aortic dilatation (>45 mm Marfan, >50 mm BAV), severe MS, vascular Ehlers-Danlos

The CARPREG II score provides further risk prediction layered onto the mWHO class, incorporating cardiac diagnosis, baseline status, and process-of-care factors.

Source: Fuster and Hurst's The Heart, 15th ed., p. 2189; Creasy & Resnik's, p. 1244

4. Specific Conditions

Valvular Heart Disease

Regurgitant lesions (MR, AR) are better tolerated - reduced SVR in pregnancy is actually beneficial
Stenotic lesions (MS, AS) are poorly tolerated - fixed obstruction cannot accommodate the 50% increase in blood volume
Mitral stenosis is the most common valvular lesion in pregnancy (rheumatic); severe MS should be corrected before pregnancy; balloon valvotomy can be performed during pregnancy if needed
Aortic stenosis (severe, symptomatic): pregnancy contraindicated (mWHO IV)
Prosthetic valves: anticoagulation management is highly challenging - warfarin crosses the placenta (teratogenic, especially 6-12 weeks; warfarin embryopathy) vs. heparin/LMWH (higher maternal thromboembolic risk). Shared decision-making required throughout pregnancy.

Hypertension and Preeclampsia

Complicates 10% of pregnancies
Gestational HTN: new-onset BP ≥140/90 after 20 weeks without proteinuria
Preeclampsia: new-onset HTN after 20 weeks + significant proteinuria or end-organ dysfunction
Severe features: BP ≥160/110, platelets <100 × 10⁹/L, pulmonary oedema, CNS symptoms (headache, visual changes), renal insufficiency, liver dysfunction
Treatment targets: BP goal <160/105 mmHg; safe first-line agents are nifedipine, labetalol, and alpha-methyldopa
Low-dose aspirin from 12-14 weeks recommended in women with chronic HTN or prior hypertensive pregnancy

Peripartum Cardiomyopathy (PPCM)

Newly diagnosed systolic cardiomyopathy (LVEF <45%) without a reversible cause, presenting in the last month of pregnancy or within 5 months postpartum
Management: standard heart failure therapy; ACE inhibitors/ARBs are contraindicated in pregnancy but can be used postpartum
Bromocriptine (prolactin antagonist) is under active investigation
Previous PPCM with any residual LV impairment = mWHO IV (pregnancy contraindicated)

Arrhythmias

Frequency increases during pregnancy
New-onset arrhythmia, especially ventricular, mandates structural cardiac evaluation
New-onset AF requires structural evaluation + rule out pulmonary embolism
SVT can often be managed with adenosine or beta-blockers

Congenital Heart Disease

Now the leading cause of cardiac disease in pregnancy in developed countries (improved surgical survival)
Functional capacity of at least 80% of general population required for safe pregnancy
Cyanotic CHD: high risk of spontaneous abortion, small-for-gestational-age, stillbirth
Maternal CHD carries ~5-10% risk of offspring having congenital cardiac malformation

Aortopathies

Marfan syndrome: aortic dissection risk increased; beta-blockade advised; aortic root >45 mm = contraindicated
Bicuspid aortic valve: aortic root >50 mm = contraindicated
Turner syndrome: aortic size index >25 mm/m² = contraindicated

5. Contraindicated Medications in Pregnancy

Drug Class	Reason
ACE inhibitors	Fetotoxic (renal dysgenesis, oligohydramnios)
ARBs	Same as ACE inhibitors
Aldosterone antagonists (spironolactone)	Anti-androgen effects on fetus
NOACs (warfarin alternatives)	Teratogenic/fetal haemorrhage
Endothelin receptor antagonists (e.g., bosentan)	Teratogenic
Riociguat	Teratogenic
Amiodarone	Only as last resort (fetal hypothyroidism)
Nitroprusside	Only as last resort (cyanide toxicity)
Atenolol	Requires shared decision-making (IUGR risk)

Source: Fuster and Hurst's The Heart, 15th ed., p. 2184

6. Management Framework

Preconception

Full cardiac assessment: vitals, SpO₂, ECG, echo, consider CT/MR angiography for aortic disease
Review and modify medications
Fetal echo at 20 weeks if maternal CHD
Genetics referral for heritable conditions
Counsel on maternal, fetal, and neonatal risks
Consider cardiac intervention before conception if indicated (allow 6-12 months recovery)

Antepartum

Multidisciplinary "Pregnancy Heart Team": cardiology, maternal-fetal medicine, anaesthesia, neonatology
Frequency of visits based on disease severity (mWHO class)
Serial echocardiography during pregnancy

Delivery

Vaginal delivery is recommended for most women with heart disease
Epidural analgesia is preferred (reduces sympathetic surge and pain)
Left lateral decubitus position to optimise venous return
Detailed delivery plan including mode, induction, analgesia, monitoring

Postpartum

Highest haemodynamic risk period is immediately postpartum (autotransfusion from uterus)
Medication review for breastfeeding safety
Baseline cardiac assessment at 6 months postpartum
Cardiovascular risk assessment for those with hypertensive complications
Contraception counselling

Cardiac Arrest in Pregnancy

Standard ACLS protocols apply - life-saving drugs should not be withheld
Key modification: manual uterine displacement 15 cm to the left to relieve aortocaval compression and improve venous return
Perimortem caesarean delivery should be performed within 5 minutes if resuscitation fails in a viable gestation

Source: Braunwald's Heart Disease, 12th ed., p. 1064; Fuster and Hurst's The Heart, 15th ed.

Key Summary Points

Heart disease is the leading cause of indirect maternal death in pregnancy
Normal pregnancy causes 50% increase in blood volume and 30-45% rise in cardiac output - major stress on diseased hearts
mWHO classification is the cornerstone of risk stratification
Stenotic lesions are poorly tolerated; regurgitant lesions are relatively well tolerated
ACE inhibitors, ARBs, NOACs, and ERAs are absolutely contraindicated
A multidisciplinary Pregnancy Heart Team is mandatory for mWHO class III-IV patients
Peripartum cardiomyopathy must be considered in any new-onset heart failure in late pregnancy or postpartum

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