Cardiovascular Disease in Pregnancy Part III: Septal Defects and Maternal Congenital Cardiac Disease

We continue our series on cardiovascular diseases with part III this week. Check out Part I and Part II if you haven’t already!

Atrial Septal Defects (ASDs) + Ventricular Septal Defects (VSDs) 

• ASD: Repaired vs. unrepaired 

  • Repaired = WHO class I - if no significant residual disease, have very low maternal cardiac risk in pregnancy.

  • Unrepaired = WHO class II 

    • Depends on size; if small → generally uncomplicated, will tolerate pregnancy well 

    • However, those with unrepaired ASDs also can have risk for supraventricular arrhythmias, like atrial flutter 

      • Remember that if there is an ASD, DVTs can travel to the systemic circulation → stroke (paradoxical embolus).

    • Also, if ASD is large and associated with significant pulmonary vascular disease, pregnancy should be avoided due to high risk of maternal and fetal mortality 

• VSD: Repaired vs. unrepaired 

  • Repaired = WHO Class I. If small VSD with shunt ratio <1.7 with normal pulmonary pressure and preserved aerobic function → no increased risk to mom or fetus during pregnancy.

    • Shunt ratio briefly: pulmonary flow/systemic flow 

    • Basically, when there is L → R shunt, because there is a backleak of blood from the left side to the right side, the pulmonary flow will always be more than the systemic flow.

      • So a large shunt ratio implies significantly more pulmonary flow compared to systemic flow.

  •  Unrepaired: if large VSD shunts, history of arrhythmia associated with shunt, ventricular dysfunction, or pulmonary hypertension → higher risk of developing cardiovascular complications in pregnancy 

    • Complications include arrhythmias and heart failure.

    • Surveillance during pregnancy for pulmonary hypertension.

• Atrioventricular septal defect 

  • After ASD repair, pregnancy is usually well tolerated (WHO Class II - III) 

  • Arrhythmias and worsening AV regurg have been described 

Tetralogy of Fallot 

• Most common cyanotic congenital heart defect. Remember PROV:

  • Pulmonary stenosis (RV outflow tract obstruction)

  • RV Hypertrophy (concentric)

  • Overriding aorta 

  • VSD 

• How to remember all this: 

  • Think this way: The aorta and the pulmonary artery trunk are next to each other in the heart. Aorta comes from the LV and the pulmonary artery from the RV. Imagine if the aorta just became really big and took over the real estate of the pulmonary artery. What has to happen? 

    • Overriding aorta 

    • Aorta takes over the real estate and therefore breaks through the ventricular septum → VSD 

    • The pulmonary artery is now super small, and therefore the pulmonic valve must be super small → RV outflow tract obstruction 

    • RV now has to work harder → RV hypertrophy 

      • So really, it’s just one thing that went wrong! 

• Repaired Tet = WHO Class II - generally good outcomes if no severe hemodynamic abnormalities before pregnancy  

  • Complications can include arrhythmias (6.4%) and heart failure (2.4%) 

  • Fetal complications = premature delivery, SGA, recurrent CHD of any type, and very small risk of fetal and perinatal mortality (0.5% and 1.4% respectively) 

  • Remember that there is a higher risk of 22q11.2 microdeletion in offspring 

    • Approximately 15% of patients with ToF and other conotruncal defects have chromosome 22q11.2 microdeletion, and genetic testing should be offered in the prenatal setting 

  • Follow up every trimester by cards, but if severe pulmonary regurg, monthly or bimonthly follow up 

• Unrepaired Tet = WHO Class III, and pregnancy is not recommended 

  • Would need close f/u with cardiology 

More rare stuff 

• Ebstein’s Anomaly 

  • What is it: Tricuspid valve is placed too low on the right ventricle → enlargement of R atrium and non-functioning tricuspid valve. 

  • Again, if uncomplicated, pregnancy is well tolerated (Who Class II) 

  • But if there is cyanosis (usually due to ASD) or heart failure → counsel against pregnancy  

• Transposition of the Great Arteries 

  • What it is: the left side of the heart pumps to the pulmonary artery and right side of the heart pumps to the aorta (basically, aorta and pulmonary artery are switched) 

  • Adults will have it corrected = arterial switch, and can usually tolerate pregnancy well if there is good clinical function pre-pregnancy 

  • Again, there is higher risk of heart failure and arrhythmias and should have good cardiology follow up 

• Fontan Circulation 

  • What is it:

    • Basically it is a palliative surgical procedure performed in patients with a functional or anatomic single ventricle 

    • Some common reasons: hypoplastic left heart syndrome, tricuspid atresia, pulmonary atresia with intact ventricular septum, etc. 

  • Essentially diverts systemic venous return to the lungs without a pump, driven by central venous pressure. The single ventricle does pump blood to the systemic circulation.

  • For this to work, the person must have a low pulmonary arteriolar resistance, and relatively normal function of the single ventricle.

  • Prior to pregnancy, those with Fontan circulation should discuss with their cardiologist and have preconception counseling with MFM 

  • Those with poor functional capacity, history of heart failure, or ventricular function <40%, arrhythmias, etc should not get pregnant due to risk of complications 

  • Complications during pregnancy: arrhythmias, thrombotic and bleeding events, ventricular dysfunction, and edema 

  • Increased risk for SAB and premature birth as well as FGR 

  • PPH has been documented in up to 50% of pregnancies 

Labor and Delivery 

• In most of these cases, patients should have telemetry intrapartum and 24 hours pp due to higher risk of arrythmias 

• Strict I/Os

• Depending on severity of case, but should consider early epidural

• Vaginal delivery is not contraindicated, but should be assessed on a case by case basis