Help me understand cardiac diseases in pregnancy as a post graduate in obgyn for my residency exams

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Cardiac Diseases in Pregnancy

A Comprehensive Guide for OB/GYN Postgraduate Residents

1. Epidemiology and Importance

Cardiovascular disease (CVD) complicates 1-4% of pregnancies and is the leading cause of indirect maternal mortality, accounting for ~37% of non-obstetric maternal deaths. This burden is increasing due to:

Advanced maternal age
Rising CVD risk factors (obesity, hypertension, diabetes)
Improved survival of congenital heart disease (CHD) patients reaching reproductive age

Predominant etiology by region:

Developed world: Congenital heart disease (most common)
Developing world: Rheumatic heart disease (most common)

2. Hemodynamic Changes in Normal Pregnancy

Understanding these is fundamental - they form the basis of why cardiac disease decompensates.

Parameter	Change	Timing/Magnitude
Blood volume	Increases 40-50%	Peaks at 28-32 weeks
Cardiac output	Increases 30-50%	Peaks at 28-32 weeks
Heart rate	Increases 10-20 bpm	Throughout
Systemic vascular resistance	Decreases 20-30%	Due to progesterone & placental shunt
Blood pressure	Decreases slightly	Nadir at mid-pregnancy
Stroke volume	Increases	Significant

During labor: Each uterine contraction returns 300-500 mL of blood to the central circulation (auto-transfusion effect), further stressing the heart.

Postpartum: Sudden relief of IVC compression + mobilization of fluid = acute increase in venous return. This is when many cardiac patients decompensate - the immediate postpartum period is a high-risk window.

Normal Physical Findings in Pregnancy (NOT signs of pathology)

Systolic murmurs in >95% of pregnant women
Third heart sound (S3) - sometimes present
Venous hums, mammary souffle
Dependent edema, rales, visible neck veins
Cardiomegaly on CXR
Dyspnea, orthopnea, easy fatigability, dizziness, occasional syncope

Findings That INDICATE Organic Heart Disease

Fourth heart sound (S4)
Diastolic murmurs (always abnormal)
Loud, harsh systolic murmurs
Cyanosis and clubbing
Sustained cardiac arrhythmias
Severe dyspnea, exertional syncope, hemoptysis, paroxysmal nocturnal dyspnea, exertional chest pain

3. Preconception Counseling

Every woman with known cardiac disease must be counseled before conception. The cardiologist and MFM specialist together should classify the patient into one of four categories:

Pregnancy is safe
Will require treatment and cause discomfort - but manageable
Carries significantly increased risk
Extremely dangerous - should not be undertaken

Conditions Requiring Treatment BEFORE Pregnancy

Large intracardiac shunts (ASD, VSD)
Significant valvular disease (severe MS, AS)
Unrepaired coarctation
Severe aortic dilatation
Significant arrhythmias

4. WHO Risk Classification (mWHO) - The Exam Favorite

The Modified WHO Classification is the standard for risk stratification.

WHO Class	Description	Maternal Mortality/Morbidity	Examples
I	No detectable increased risk	Negligible	Small ASD/VSD (repaired), MVP with trivial MR, isolated ectopics
II	Small increased risk	Slight increase	Unrepaired ASD/VSD, repaired TOF, most arrhythmias, Turner without aortic dilatation
II-III	Moderate risk (case-by-case)	Moderate increase	Mild LV dysfunction (EF 45-54%), HOCM, native or tissue valve not class I/IV, Marfan without aortic dilatation, <45 mm aorta in bicuspid AV
III	Significantly increased risk	Significant - expert care required	Mechanical valve, systemic RV, Fontan, complex CHD, aorta 40-45 mm in Marfan, aorta 45-50 mm in BAV
IV	Extremely high risk - pregnancy contraindicated	Very high morbidity/mortality	PAH, severe systemic ventricular dysfunction (EF <30% or NYHA III-IV), previous PPCM with residual LV impairment, severe symptomatic AS, severe MS, severe (re)coarctation, vascular Ehlers-Danlos, aorta >45 mm in Marfan, >50 mm in BAV, Turner with ASI >25 mm/m²

High-yield point for exams: WHO Class IV = Pregnancy is contraindicated

5. CARPREG Risk Score

The CARPREG score (Cardiac Disease in Pregnancy) predicts adverse cardiac events:

One point each for:

Prior cardiac event (heart failure, TIA, stroke, arrhythmia before pregnancy)
Poor functional class (NYHA ≥ III or cyanosis)
Left heart obstruction (MVA <2 cm², AVA <1.5 cm², peak LVOT gradient >30 mmHg)
Systolic ventricular dysfunction (EF <40%)

Risk of adverse event:

0 points = 5% risk
1 point = 27% risk
1 point = 75% risk

6. Specific Cardiac Conditions

6a. Rheumatic Heart Disease - Valvular Lesions

Mitral Stenosis (MS) - THE most dangerous valvular lesion in pregnancy

Why it's dangerous: Pregnancy increases heart rate → reduces diastolic filling time → raises left atrial pressure → pulmonary edema. The fixed obstruction cannot accommodate the 40-50% increase in cardiac output.

Feature	Detail
Most common cause	Rheumatic fever
Critical MVA	<1.0 cm² = severe; <1.5 cm² = significant
Peak risk period	28-32 weeks, labor, immediate postpartum
Key complication	Pulmonary edema, AF with rapid ventricular rate
Fetal risks	Prematurity 20-30%, IUGR 5-20%, stillbirth 1-3%

Management:

Reduce heart rate: Beta-blockers (metoprolol) - first-line; decrease HR to allow diastolic filling
Diuretics: For pulmonary edema (furosemide - safe in pregnancy)
Anticoagulation: If AF, LA enlargement (≥60 mL/m²), or spontaneous echo contrast - use LMWH/UFH (NOT warfarin in 1st trimester, NOT DOACs ever in pregnancy)
Percutaneous mitral valvuloplasty (PMV): If refractory to medical therapy, suitable valve anatomy - best after 20 weeks, with fetal radiation protection
Delivery: Most can deliver vaginally. CS for severe MS with NYHA III/IV + pulmonary hypertension despite optimal treatment

Mitral Regurgitation (MR)

Generally well tolerated in pregnancy
The decreased SVR in pregnancy actually reduces the regurgitant fraction
Treat with diuretics and vasodilators if symptomatic

Aortic Stenosis (AS)

Most common cause in reproductive age: Bicuspid aortic valve (BAV)
Asymptomatic women with normal exercise capacity and normal BP response to exercise can often tolerate pregnancy
Women with severe symptomatic AS (or EF <50%) should have intervention BEFORE pregnancy
BAV associated with aortic root dilatation - increased risk of aortic dissection; MRI pre-pregnancy to assess aortic dimensions
Safe if ascending aorta <50 mm (or <27 cc/m²)
Fetal risks: Heart failure ~10%, arrhythmia ~25%; preterm delivery, IUGR, low birth weight up to 35%

Aortic Regurgitation (AR)

Generally well tolerated (decreased SVR reduces regurgitation)
Treat symptomatically; diuretics if needed

Mitral Valve Prolapse (MVP)

Isolated MVP with trivial MR = WHO Class I - benign in pregnancy

6b. Prosthetic Heart Valves - A Major Exam Topic

Bioprosthetic Valves

Preferred for women of childbearing age
Do NOT require anticoagulation (only low-dose aspirin)
BUT: Pregnancy may accelerate valve deterioration/structural failure

Mechanical Valves - The Anticoagulation Dilemma

This is one of the highest-stakes clinical problems in cardiac obstetrics:

Anticoagulant	Maternal thrombosis risk	Fetal risk
Warfarin	Best (lowest valve thrombosis risk)	Warfarin embryopathy (1st trimester): nasal hypoplasia, optic atrophy, digital anomalies, mental impairment - risk ~5% (lower if dose <5 mg/day); fetal/intrauterine bleeding
UFH/LMWH	Higher maternal risk (valve thrombosis)	Safe for fetus (do not cross placenta)

Key management principle (ESC guideline):

First trimester (up to 12 weeks): Switch to UFH or LMWH (to avoid teratogenicity), OR continue warfarin if dose ≤5 mg/day after thorough counseling
Second and third trimester: Warfarin (superior anticoagulation for valve)
Before delivery (36 weeks): Switch back to IV UFH (easily reversible); discontinue 4-6 hours before delivery

DOACs (rivaroxaban, apixaban, dabigatran) are absolutely CONTRAINDICATED in pregnancy.

6c. Congenital Heart Disease (CHD)

Atrial Septal Defect (ASD)

Usually well tolerated
Risk: Paradoxical embolism (venous clot crossing through ASD into systemic circulation), arrhythmia
Large unrepaired ASD: risk of AF, paradoxical embolism
Eisenmenger's ASD = WHO Class IV (contraindicated)

Ventricular Septal Defect (VSD)

Small, restrictive VSD (maladie de Roger): Well tolerated, WHO Class I-II
Large VSD with Eisenmenger physiology: Contraindicated
Pregnancy-specific risk: Increased preeclampsia even with unrepaired VSD

Patent Ductus Arteriosus (PDA)

Small PDA: No hemodynamic significance
Large PDA: Pulmonary hypertension risk
Ductal flow decreases in pregnancy (SVR falls)

Eisenmenger Syndrome

Classic WHO Class IV - Pregnancy absolutely contraindicated
Any left-to-right shunt that has reversed to right-to-left due to pulmonary hypertension
Maternal mortality: 30-50%
Should be offered termination of pregnancy if already pregnant

Tetralogy of Fallot (TOF)

Repaired TOF: Generally tolerated, WHO Class II-III
Women with dilated RV and preserved RV function: Pregnancy does not worsen RV size/function
Unrepaired TOF: High risk - discourage pregnancy, advise surgical repair first
Key concern: Pulmonary regurgitation (from prior repair), RV dilation, arrhythmia

Coarctation of the Aorta

Key feature: Higher BP in arms vs. legs, radial-femoral pulse delay, late systolic murmur (interscapular)
Most common complication in pregnancy: Systemic hypertension
Risk: Aortic dissection (especially if associated bicuspid AV), LV failure, reduced fetal perfusion
Blood pressure control throughout pregnancy is imperative
Safe if ascending aorta < coarctation dimensions are controlled

Ebstein Anomaly

Outcome relates to degree of tricuspid displacement, TR, RV dysfunction, cyanosis, arrhythmia
Overall risk of HF or arrhythmia: <5%
WPW syndrome in ~20% → risk of AF → life-threatening hemodynamic deterioration
Atrial communication → risk of paradoxical embolism, cyanosis

Transposition of Great Arteries (TGA) - post-Mustard/Senning

Morphological RV functions as systemic ventricle
Systemic ventricular failure in pregnancy: 5-10%
Ventricular dimensions/function may not return to baseline after pregnancy

Fontan Palliation

Single ventricle circulation
WHO Class III-IV - any complication = Class IV contraindication
Very high risk; requires expert multidisciplinary management

6d. Cardiomyopathies

Peripartum Cardiomyopathy (PPCM) - THE signature cardiac emergency of pregnancy

Definition (ESC/HFSA): New onset of HF in the last month of pregnancy or within 5 months of delivery with LV systolic dysfunction (EF <45%), no pre-existing heart disease, no other identifiable cause.

Epidemiology: 1:300 - 1:4000 deliveries; higher in:

Black women
Multiparity
Twin pregnancy
Advanced maternal age
Pre-eclampsia
Malnutrition

Pathophysiology (key mechanisms):

Prolactin cleavage by cathepsin-D → 16 kDa prolactin fragment → antiangiogenic, proapoptotic, proinflammatory
Oxidative stress, viral myocarditis, microchimerism
STAT3 pathway dysfunction

Clinical features:

Symptoms of HF: dyspnea, orthopnea, PND, lower limb edema, fatigue
Elevated JVP, displaced apex, S3, mitral regurgitation murmur
CXR: Cardiomegaly, pulmonary congestion
Echo: Dilated LV, EF <45%, may have thrombus

Management:

Antepartum: Standard HF therapy modified for pregnancy:
- Diuretics (furosemide)
- Beta-blockers (carvedilol/metoprolol - avoid atenolol)
- Hydralazine + nitrates (instead of ACEi/ARB - teratogenic)
- Bromocriptine: 2.5 mg twice daily for 2 weeks, then 2.5 mg daily for 4 weeks - to block prolactin production (evidence from RCTs)
- Anticoagulation if EF <35% (high thromboembolic risk)
Postpartum: ACEi/ARB can now be added (key change after delivery)
Bromocriptine inhibits breastfeeding (suppress prolactin)

Prognosis:

~50% recover to normal EF within 6 months
~25% have persistent LV dysfunction
Mortality: ~2-8% in developed countries, higher in Africa

Key exam point: Previous PPCM with residual LV impairment = WHO Class IV (pregnancy contraindicated)

Hypertrophic Cardiomyopathy (HCM)

Most women with HCM tolerate pregnancy well
Risk: Worsening of LV outflow tract obstruction (LVOTO) due to decreased SVR and increased HR
Beta-blockers should be continued throughout pregnancy
Avoid vasodilators, diuretics (reduce preload → worsen obstruction)
Delivery: Epidural analgesia with careful fluid management; avoid Valsalva

Dilated Cardiomyopathy

Poor toleration if EF <40% (WHO Class III-IV)
If EF <30% or NYHA III-IV → WHO Class IV - contraindicated

6e. Cardiac Arrhythmias

Palpitations are common in pregnancy, but rarely signify organic disease. ECG changes in normal pregnancy include:

Left axis shift (elevated diaphragm)
Nonspecific ST-T changes in lead III, aVF
Small Q waves occasionally

Supraventricular Tachycardia (SVT):

Vagal maneuvers first
Adenosine: Safe, first-line for acute termination
Metoprolol or verapamil: For prevention
Digoxin: Rate control in AF/flutter

Atrial Fibrillation/Flutter:

Rate control: Beta-blockers, digoxin, non-DHP CCBs (verapamil, diltiazem)
Rhythm control: DC cardioversion (safe at any gestational age)
Anticoagulation: LMWH/UFH - for AF with significant MS, LA enlargement, echo contrast
DOACs absolutely contraindicated
Catheter ablation: Ideally postponed until after delivery; radiation precautions if essential

Ventricular Arrhythmias:

Lidocaine: First-line for acute VT
Mexiletine: Probably safe - limited data
Amiodarone: Last resort only - fetal hypothyroidism, neonatal thyroid suppression

Bradyarrhythmias:

Pacemaker implantation: Safe in pregnancy with radiation shielding

6f. Pulmonary Arterial Hypertension (PAH)

WHO Class IV - Pregnancy absolutely contraindicated
Maternal mortality: 25-56%
Mechanism: Fixed pulmonary vascular resistance cannot accommodate the increase in cardiac output of pregnancy → right heart failure
If already pregnant: Termination recommended early
If continuing despite advice: Expert center management with pulmonary vasodilators (treprostinil, sildenafil), careful monitoring

6g. Ischemic Heart Disease / SCAD

Rare in reproductive age, but increasing (advanced maternal age, obesity, hypertension, smoking)
Spontaneous Coronary Artery Dissection (SCAD): Increasingly recognized pregnancy-associated cause of MI
- Mechanism: Hormonal changes → medial smooth muscle weakening, connective tissue loosening → intramural hematoma
- Most common in LAD
- Management: Conservative (antiplatelet) vs. PCI/CABG depending on hemodynamic stability
Conventional MI in pregnancy: PCI preferred over thrombolytics (risk of maternal hemorrhage)

6h. Aortic Diseases

Marfan Syndrome:

Aorta >45 mm → WHO Class IV
Aorta 40-45 mm → WHO Class III
Aorta <40 mm → may proceed with close monitoring
Risk: Aortic dissection (especially in 3rd trimester and peripartum)
Beta-blockers throughout pregnancy (reduce aortic wall stress)
CS recommended if aorta >40 mm

Bicuspid Aortic Valve (BAV):

Aorta >50 mm → contraindicated
Aorta 45-50 mm → individual assessment (WHO III)
Regular cardiac MRI/echo to monitor aortic dimensions

7. Hypertensive Disorders of Pregnancy (Brief Cardiac Relevance)

Category	Definition
Gestational hypertension	New onset BP ≥140/90 after 20 weeks, no proteinuria/end-organ damage
Preeclampsia	New BP ≥140/90 after 20 weeks + proteinuria OR end-organ damage
Chronic hypertension	BP elevation before 20 weeks or pre-pregnancy
Chronic HTN + superimposed PET	Chronic HTN + new proteinuria or end-organ damage

Severe features of preeclampsia:

SBP ≥160 or DBP ≥110 mmHg (at least 4 hours apart)
Platelets <100 × 10⁹/L
Pulmonary edema
CNS symptoms (persistent headache, visual changes)
Creatinine >1.1 mg/dL or doubling of baseline
Liver enzymes >2× upper normal + RUQ/epigastric pain

Antihypertensive drugs in pregnancy:

First-line: Methyldopa, Labetalol, Nifedipine (extended-release)
Contraindicated: ACEi, ARBs, direct renin inhibitors, aldosterone antagonists (spironolactone)
For acute severe hypertension: IV labetalol, oral/sublingual nifedipine, IV hydralazine

8. Cardiovascular Drugs in Pregnancy - Safety Summary

Drug	Use	Safety
Methyldopa	Hypertension	Safe - first-line
Labetalol	HTN, arrhythmia	Safe
Metoprolol/propranolol	Arrhythmia, HCM	Safe (monitor neonate: hypoglycemia, bradycardia, RDS)
Atenolol	HTN	Avoid (associated with IUGR) - requires shared decision-making
Nifedipine	HTN	Safe
Verapamil/diltiazem	Rate control	Safe (2nd/3rd trimester)
Digoxin	Rate control	Safe
Furosemide	HF/edema	Safe
Heparin (UFH/LMWH)	Anticoagulation	Safe (don't cross placenta)
Warfarin	Mechanical valves	Teratogenic (1st trimester), fetal bleeding - use with strict protocols
DOACs	Any	Absolutely CONTRAINDICATED
ACEi/ARBs	-	Absolutely CONTRAINDICATED (fetal renal agenesis, oligohydramnios, skull ossification defects)
Aldosterone antagonists	-	Contraindicated
Endothelin receptor antagonists	-	Contraindicated
Adenosine	Acute SVT	Safe
Lidocaine	Acute VT	Safe
Amiodarone	VT/VF	Last resort only (fetal hypothyroidism)
Nitroprusside	Hypertensive emergency	Last resort (fetal cyanide toxicity)
Bromocriptine	PPCM	Use cautiously - inhibits breastfeeding
Hydralazine	HF, hypertension	Safe (lupus-like syndrome with long use)

9. Delivery Considerations

Mode of Delivery

General principle: Mode of delivery is guided by obstetric indications - most women with CVD can deliver vaginally
Cesarean section for obstetric indications, not cardiac disease alone (exception: very severe, critically ill patients)

Second Stage Management

Historically: Valsalva avoided in all cardiac patients
Current evidence: Passive second stage (allow head to descend to low station) → then trial of pushing
Forceps/vacuum: If hemodynamic compromise during active pushing
Assisted second stage considered for: Severe AS, severe MS, PAH, aortic disease, Marfan >40 mm aorta

Anesthesia

Epidural: Preferred for pain relief - reduces catecholamine surge, decreases HR and BP
Avoid large fluid boluses (especially in MS, PAH)
For Eisenmenger/PAH: Epidural with very careful titration; avoid systemic hypotension

Postpartum Period

Critical danger period - especially first 24-48 hours postpartum
Autotransfusion from uterine involution
ACEi/ARB can NOW be initiated (postpartum) for HF management
Bromocriptine for PPCM (suppresses lactation if EF very low)
Ergometrine/methylergonovine: Avoid in cardiac patients (causes intense vasospasm, HTN)
Oxytocin: Use diluted infusion (not IV bolus - causes hypotension, tachycardia)

10. CPR in Pregnancy

ACLS protocols apply with one critical modification:
Manual left uterine displacement - displace the uterus leftward by ~1.5 cm to relieve aortocaval compression and improve venous return
If no ROSC after 4 minutes: Perimortem cesarean section (within 5 minutes of cardiac arrest) - improves maternal CPR success AND fetal survival

11. High-Yield Exam Summary

Topic	Key Point
Most dangerous valvular lesion	Mitral stenosis
WHO Class IV conditions	PAH, severe LV dysfunction (EF <30%, NYHA III-IV), PPCM with residual LV impairment, severe AS, severe MS, Marfan with aorta >45 mm, vascular EDS, Fontan with complications, Eisenmenger
Safest anticoagulant for fetus	LMWH/UFH (don't cross placenta)
Best anticoagulant for mechanical valves	Warfarin (but teratogenic 1st trimester)
Never use in pregnancy (anticoagulation)	DOACs
Never use in pregnancy (antihypertensive)	ACEi, ARBs
PPCM definition timing	Last month of pregnancy to 5 months postpartum
PPCM specific therapy	Bromocriptine (inhibits prolactin/16 kDa fragment)
Key drug for MS in pregnancy	Beta-blockers (metoprolol) - slow HR, improve filling
CPR modification	Left uterine displacement + perimortem CS if no ROSC at 4 min
Eisenmenger maternal mortality	30-50%
PAH maternal mortality	25-56%
PPCM recovery rate	~50% recover EF within 6 months
Second stage management	Passive second stage preferred; assisted if hemodynamically compromised
Oxytocin use	Diluted infusion only - NOT IV bolus (hypotension/tachycardia)
Ergometrine/methergine	Absolutely avoid in cardiac patients (vasospasm, HTN)

Sources: Creasy & Resnik's Maternal-Fetal Medicine (8th Ed.), Fuster and Hurst's The Heart (15th Ed.), Braunwald's Heart Disease

This covers the major exam-relevant topics for a PG OB/GYN resident. If you want deeper coverage of any specific condition (e.g., PPCM management algorithms, mechanical valve anticoagulation protocols, PAH in detail, or delivery planning for specific lesions), just ask!

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