Cardiac disease in pregnancy

Physiologic Changes - The Overworked Pump

• Blood Volume: ↑ 40-50%, with plasma volume increasing more than red cell mass, causing physiologic anemia.
• Cardiac Output (CO): ↑ 30-50%, peaking in the second trimester. Driven by ↑ stroke volume and ↑ heart rate (15-20 bpm).
• Systemic Vascular Resistance (SVR): ↓ ~20% due to progesterone-mediated smooth muscle relaxation and AV shunting to the placenta.
• Physical Exam: Expect peripheral edema, a systolic flow murmur, and a third heart sound (S3).

⭐ Exam Favorite: Blood pressure, particularly diastolic, reaches its lowest point (nadir) during the second trimester. This can mask a diagnosis of chronic hypertension if the first prenatal visit occurs during this period.

Risk Stratification - Gauging the Danger

• WHO Classification (Modified): Stratifies maternal cardiovascular risk from I (low) to IV (extremely high).

  • WHO I: Uncomplicated, repaired lesions (e.g., PDA, ASD).
  • WHO II: Most arrhythmias, unrepaired ASD/VSD.
  • WHO III: Mechanical valves, Fontan circulation, cyanotic heart disease.
  • WHO IV (Contraindicated): Severe pulmonary arterial hypertension (PAH), LVEF <30%, severe mitral stenosis.

• CARPREG II Score: Predicts adverse maternal cardiac events based on:

  • Prior cardiac event (heart failure, TIA, arrhythmia).
  • NYHA class >II or cyanosis.
  • Left heart obstruction.
  • Reduced systemic ventricular function (LVEF <40%).

⭐ Severe pulmonary hypertension (WHO Class IV) carries the highest risk of maternal mortality, approaching 30-50%.

Specific Conditions - When Hearts Falter

• Mitral Stenosis: Most common rheumatic valvular lesion in pregnancy. Poorly tolerated due to ↑ plasma volume causing ↑ left atrial pressure & pulmonary edema. Manage with β-blockers & diuretics.

• Peripartum Cardiomyopathy (PPCM): Idiopathic heart failure in the last month of pregnancy or within 5 months postpartum.

  • Diagnosis: New-onset LV systolic dysfunction (LVEF < 45%).
  • Management: Standard heart failure therapy (hydralazine, nitrates, diuretics). Avoid ACE inhibitors/ARBs during pregnancy.

• Eisenmenger Syndrome: Severe pulmonary HTN with a reversed (right-to-left) shunt. Carries the highest maternal mortality risk (>50%); pregnancy is contraindicated.

⭐ Exam Favorite: Risk of PPCM recurrence is 30-50%. Counsel patients on the high risk with future pregnancies, especially if LV function has not completely recovered.

Management - The Final Gauntlet

• Multidisciplinary team (Cardiology, MFM, Anesthesia) guides peripartum care.
• Goal: Minimize cardiac stress. Vaginal delivery is preferred.
• Anesthesia: Early epidural to blunt catecholamine surge from pain.

⭐ The greatest hemodynamic shifts and risk of decompensation occur immediately postpartum. Autotransfusion from the involuting uterus adds ~500 mL of volume to central circulation, which can overwhelm a compromised heart.

High‑Yield Points - ⚡ Biggest Takeaways

• Physiologic cardiovascular changes (↑ cardiac output, ↓ SVR) can unmask or worsen underlying heart disease.
• The highest risk period for decompensation is at 28-32 weeks gestation and the immediate postpartum period.
• Mitral stenosis is the most common rheumatic lesion and is poorly tolerated due to tachycardia and volume load.
• Peripartum cardiomyopathy is a diagnosis of exclusion for new-onset heart failure in late pregnancy or postpartum.
• Management favors vaginal delivery with epidural analgesia to minimize cardiac strain.
• ACE inhibitors, ARBs, and warfarin are contraindicated during pregnancy.