"Hole in the Heart" — Cardiac Septal Defects

Types and Anatomy

Atrial Septal Defect (ASD)

Ventricular Septal Defect (VSD)

Key distinction: VSDs are more common overall but most close spontaneously in childhood. ASDs rarely close on their own, which is why ASD is the most common congenital heart defect in adults. — Robbins, Cotran & Kumar Pathologic Basis of Disease

Pathophysiology

• Right heart volume overload → RV and RA enlargement
• Increased pulmonary blood flow
• Large shunts (Qp/Qs >3:1) → progressive right heart failure
• Risk of paradoxical embolism (thrombus crosses to systemic circulation)
• Long-term: pulmonary hypertension → can reverse to right-to-left shunt (Eisenmenger syndrome)

• Small defects: minimal effect, often asymptomatic
• Moderate/large defects: LV and LA dilation, elevated pulmonary artery pressure
• ~10% of large VSDs develop Eisenmenger complex

— Goldman-Cecil Medicine

Clinical Features

ASD in Women — Why It Matters

• ASDs are often silent for decades — many women are diagnosed for the first time during pregnancy or routine workup in their 30s–50s
• >70% become symptomatic by the fifth decade

• Dyspnea on exertion, fatigue
• Palpitations (atrial fibrillation/flutter — more common in older women)
• Syncope
• Stroke (paradoxical embolism — classically in young women with no obvious cause)
• Signs of right heart failure (leg swelling, elevated JVP) — in advanced disease

• Wide, fixed splitting of S2 ← hallmark sign
• Soft pulmonary ejection systolic murmur (2nd left intercostal space)
• Mid-diastolic murmur at lower left sternal border (if large shunt → increased tricuspid flow)

VSD

• Small VSD: Loud pansystolic murmur (Grade 4+), widely radiating, maximal at left sternal border — but paradoxically, louder murmur = smaller defect (restrictive VSD)
• Large VSD: Signs of heart failure, dyspnea, poor feeding (in infants), eventually Eisenmenger syndrome

Investigations

Sinus venosus ASDs can be missed on TTE — TEE or cardiac MRI is needed if clinical suspicion remains. — Goldman-Cecil Medicine

Treatment

ASD Closure

• In patients >40 years with symptoms + significant shunt: closure improves functional status and survival
• Closure is not indicated when pulmonary vascular resistance is severely elevated (Eisenmenger)

VSD

• Small VSDs: Observation; prophylaxis against infective endocarditis
• Moderate/large VSDs: Surgical patch closure or catheter-based device closure
• Eisenmenger VSD: Medical management (pulmonary vasodilators); transplant consideration

Pregnancy Considerations (Women)

• Uncomplicated ASD without pulmonary hypertension = low risk pregnancy overall
• The physiologic murmur of pregnancy can mask ASD — diagnosis may be missed; clue is fixed S2 splitting
• Small risk of paroxysmal atrial flutter/fibrillation → managed with low-dose β-blockers or calcium channel blockers
• IV line precautions during labor: air bubbles or thrombus can cause paradoxical embolism
• Previously repaired ASD (surgical patch): risk of intraatrial reentrant tachycardia; echocardiographic evaluation recommended before pregnancy
• DOACs contraindicated in pregnancy for anticoagulation if AF develops

If a woman with unrepaired ASD is unwilling to undergo closure pre-pregnancy, she can be reassured that the risk is low provided pulmonary hypertension is absent. — Creasy & Resnik's Maternal-Fetal Medicine

Key Clinical Pearls for Women

1. Stroke in a young woman with no obvious cause → think PFO/ASD and paradoxical embolism
2. New AF in middle-aged woman → screen for undiagnosed ASD
3. Fixed splitting of S2 is not a normal finding in pregnancy — investigate
4. ASD closure before pregnancy is preferred when feasible — reduces arrhythmia risk
5. Non-coding RNA dysregulation (particularly miRNAs) is emerging as a mechanism in ASD pathogenesis (PMID 39172906, systematic review 2024)

Eisenmenger Syndrome — The Diagnosis This Woman Has

What Has Happened: The Progression

"Eisenmenger syndrome occurs when patients with a left-to-right shunt develop irreversible pulmonary vascular injury and severe PAH in response to pulmonary overcirculation. When PVR surpasses SVR, shunt direction reverses, leading to cyanosis." — Braunwald's Heart Disease

• Large unrepaired VSD, PDA, AVSD → Eisenmenger develops in early childhood
• Unrepaired ASD (<10%) → Eisenmenger develops in adulthood — and is more common in women

Clinical Features

Signs & Symptoms

Multi-organ Imaging

Why "Maintain Constant Weight"

• Sluggish flow → thrombosis → stroke/paradoxical embolism
• Hemorrhage (paradoxically — platelet dysfunction)

Maintaining stable weight keeps fluid balance constant, avoids dehydration, and prevents the hyperviscosity crises that could be life-threatening. — Braunwald's Heart Disease

Why Pregnancy is Absolutely Contraindicated

"Pregnancy is absolutely contraindicated in Eisenmenger syndrome as it is associated with very high levels of maternal mortality (>30%) and fetal loss." — Braunwald's Heart Disease

"Cyanosis associated with Eisenmenger syndrome carries an extremely high maternal mortality rate (at least 50%). Women with Eisenmenger syndrome are advised against pregnancy." — Fuster & Hurst's The Heart

Why pregnancy is so lethal in Eisenmenger:

1. Drop in SVR (normal in pregnancy) → worsens right-to-left shunting → worsening cyanosis
2. Hypercoagulable state of pregnancy + erythrocytosis → catastrophic thromboembolism risk
3. Increased cardiac demand cannot be met by a fixed pulmonary circuit
4. Fetal loss rate ~27% even if mother survives
5. Valsalva maneuver during labor → acute R→L shunt surge → cardiovascular collapse

Safe Contraception Options for Women with Eisenmenger:

• ✅ Intrauterine device (IUD) — hormonal or copper
• ✅ Depo-Provera (progesterone injection)
• ✅ Nexplanon (progesterone subdermal implant)
• ❌ Estrogen-containing pills/patches — contraindicated (thrombosis risk)
• Surgical sterilization — less commonly recommended now given less invasive options, but remains an option at an experienced ACHD center

If pregnancy does occur, early termination is strongly encouraged, carried out at a center with Adult Congenital Heart Disease (ACHD) expertise due to anesthetic risks. — Creasy & Resnik's Maternal-Fetal Medicine

Management of Eisenmenger Syndrome

Where to Be Managed

Medical Treatment

Advanced/End-Stage

• Combined heart-lung transplantation or lung transplantation + cardiac repair
• 15-year post-transplant survival: ~41%
• Only for refractory disease with advanced symptoms

NOT Appropriate

• Septal defect closure — contraindicated once Eisenmenger is established; closing the shunt removes the "pressure release valve" for the right heart and can be acutely fatal

Prognosis