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

Peripartum Cardiomyopathy

What is Peripartum Cardiomyopathy? 

• Definitions:

  • Potentially life-threatening pregnancy-associated disease that typically arises in the peripartum period and is marked by left ventricular dysfunction and heart failure - from Arany Z, Elkayan U. Peripartum Cardiomyopathy in Circulation from April 2016.

    • It’s not a precisely defined entity, because timing can vary. 

  • The US National Heart, Lung, and Blood Institute (NHLBI) in the 1990s defined PPCM as heart failure that develops in the last month of pregnancy or up to 5 months postpartum

    • This excludes patients that have pre-existing cardiomyopathies, but there are patients who otherwise meet criteria for PPCM who are <36 weeks.

  • Many definitions require cardiomyopathy to demonstrate reduced LV systolic function, where LVEF < 45%, fractional shortening <30%, or both.

• Epidemiology:

  • Ranges from 1/1000 to 1/4000 live births, but potentially increasing.

  • Proposed reasons: 

    • Increasing maternal age, preeclampsia, and multiple gestations, which are all risk factors for PPCM.

    • Also increasing HTN, diabetes, and obesity.

    • Also just growing recognition of PPCM as a disease entity.

• Symptoms/Signs:

  • Usual symptoms of heart failure:

    • Ie. fatigue, shortness of breath, increased extremity swelling, sometimes arrhythmias from overstretching of the heart.

  • Signs on exam:

    • Evidence of left sided congestion (pulmonary rales), right side congestion (ie. increased JVP and edema) 

    • Elevated BNP (Malhame in Green Journal 2019) 

    • EKG may show non-specific changes like LBBB pattern

    • Chest Xray: may show pulmonary edema and enlarged cardiac silhouette 

    • Echo: LV dilation of variable degrees, LV systolic dysfunction, RV and bi-atrial enlargement; LVEF < 45%  

What causes PPCM? 

• Older hypothesis: triggered by viral myocarditis 

  • However, a study that looked at endomyocardial biopsies in patients with PPCM and other types of cardiomyopathies, the same proportion of specimens in each group had detectable viral genomes (30%).

• Current hypothesis: “two hit” model 

  • Vascular insult - due to antivascular or hormonal effects of late pregnancy and early postpartum period → cardiomyopathy in women with an underlying predisposition.

  • There is also question of genetic predisposition 

  • High prevalence of pre-eclampsia in women with PPCM suggests a possible shared pathophysiology - perhaps some type of placental angiogenic factor.

How do we manage PPCM? 

• Prognosis: 

  • 50-80% of women with PPCM recover to normal range LVEF (>50%) with most recovery occurring within the first 6 months.

    • This is pretty good considering that in the early 1970s, the mortality of PPCM was 30-50%.

  • LV size and EF at time of diagnosis most strongly predict LV recovery.

    • LVEF <30% and LV end-diastolic diameter > 6 cm are indicative of decreased likelihood of left ventricular recovery and increased risk of mechanical support, transplant, and death.

  • 25% of patients will develop chronic heart failure, and mortality rate is still 6-10% in the United States (depending on follow up defined for mortality rate by study).

• Complications

  • One study found that 2.6% of women with PPCM in the US had cardiogenic shock, 1.5% of them needed mechanical circulatory support, and 0.5% of women underwent cardiac transplantation.

  • VTE is one of the most common severe complications of PPCM - affect 6.6% of women.

    • Mechanism: underlying intracardiac thrombosis in PPCM d/t cardiac dilatation and hypocontractility → blood stasis.

    • Also pregnancy is a hypercoagulable state.

  • Arrhythmias - can contribute to morbidity and mortality d/t death from VTach.

    • 2.1% of women with PPCM had cardiac arrest and 2.9% underwent implantation of a cardiac device.

• Treatment 

  • Few studies performed specifically in women with PPCM, so management strategies are generally extrapolated from other forms of heart failure.

  • Multidisciplinary care: MFM, anesthesia, and cardiology.

  • Individualized discussion of delivery timing for optimal maternal-neonatal outcome.

  • Usually don’t need to do a cesarean.

    • Hemodynamic shifts may be mitigated by slow epidural and assisted second stage of labor.

  • Care overall is usually supportive, directed toward managing heart failure symptoms.

    • Diuresis (but don’t go overboard and cause hypotension) 

    • If hemodynamics permit, beta blockers should be used, with preference of B1 selective ones (ie. metoprolol).

      • B2 blockers may prompt uterine activity, so better to avoid.

    • ACE-inhibitors and ARBs are considered contraindicated in pregnancy, but can use them postpartum.

    • Consider anticoagulation in PPCM if LVEF < 30% 

    • If arrhythmias, may require acute or chronic administration of antiarrythmic drugs.

  • Cardiac assisted devices - may be indicated if severe depression of LV function or if concerned for rapid deterioration.

• After PPCM, future pregnancy: 

  • Avoid future pregnancy if EF fails to improve, as mortality increases up to 50% if EF does not improve!

Cardiovascular Disease in Pregnancy Part I: Normal Physiology

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Basic Heart Function

Right Heart

• Blood flows from the SVC + IVC → R atrium → tricuspid valve (3 leaflets) → R ventricle → pulmonary valve (3 leaflets) → pulmonary artery (or pulmonary trunk), which then divides to right and left pulmonary artery → lungs.

• What happens if the right heart fails?

  • R sided heart failure basically means that the right side of the heart is not pumping out as much blood to the lung that is coming in from the peripheral veins (blood in > blood out).

    • This leads to blood backing up into the systemic circulation → lower extremity edema, hepatomegaly, jugular venous distention.

    • One of the most common causes is left heart failure.

    • Other acute causes:: pulmonary embolism with large clot burden, adult respiratory distress syndrome, RV myocardial infarction, myocarditis.

    • Causes of chronic right heart failure: pulmonary hypertension, pulmonary arterial hypertension (which is different from PH!), COPD, OSA, congenital heart disease, cardiomyopathies, or right sided valve disease.

Left Heart 

• Oxygenated blood from lungs → left atrium → mitral valve (2 leaflets) → left ventricle → aortic valve (3 leaflets) → aorta & systemic circulation 

• What happens if the left heart fails?

  • Left heart failure again means that the left side of the heart is not pumping out as much blood to the body as is coming in (blood in > blood out).

    • This leads to blood backing up into the pulmonary circulation → pulmonary edema, which can lead to SOB, coughing, etc 

    • Causes of left heart failure: myocardial infarction, dilated cardiomyopathy, left sided valvular disease, hypertension, congenital heart disease 

How does the cardiovascular system change with pregnancy? 

Hemodynamic changes

• Antepartum 

  • Throughout pregnancy, there is a continuous increase in maternal cardiac output and plasma volume.

  • There is a decrease in maternal systemic vascular resistance.

  • Blood pressure will decrease initially, but will increase in 3rd trimester.

• Intrapartum and postpartum 

  • During labor and delivery, there is increase in cardiac output, heart rate, blood pressure, and plasma volume 

  • Immediately postpartum, there is a large fluid shift (500 cc of autotransfusion), as blood flow to the gravid uterus shifts back to maternal circulation 

  • Blood pressure may increase between days 3-6 because of fluid shifts 

  • All of these shifts will make women with cardiac disease more prone to fluid overload and pulmonary edema.

Structural changes 

• The heart itself will increase in size with pregnancy 

• The left and right ventricular mass increase by approximately 50 and 40% 

• LV end diastolic volumes increase by 10% 

• Approximately 20% of women have diastolic dysfunction at term → dyspnea on exertion 

• Structural changes return to baseline after 1 year postpartum 

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ACOG PB 212