What are the maternal cardiac complications associated with pregnancy, particularly in women with pre-existing heart conditions?

Maternal Cardiac Complications Associated with Pregnancy

Cardiovascular disease is the leading single cause of maternal mortality during pregnancy, with women experiencing a spectrum of complications ranging from heart failure and arrhythmias to life-threatening events like spontaneous coronary artery dissection and aortic dissection. 1

High-Risk Cardiac Complications by Category

Life-Threatening Complications with Highest Mortality

Pulmonary hypertension carries the highest maternal mortality risk at 30-50%, making pregnancy contraindicated in these patients. 1 The severe pulmonary vascular disease—whether with or without septal defects (Eisenmenger syndrome)—leads to life-threatening rises in pulmonary vascular resistance due to pulmonary thrombosis or fibrinoid necrosis, particularly during the peripartum and postpartum periods. 1

• Severe left ventricular outflow tract obstruction poses critical risk because the fixed outflow resistance cannot accommodate the 40-50% increase in cardiac output, leading to heart failure and detrimental rises in left ventricular pressure. 1
• Aortic dissection accounts for 11% of cardiac deaths in pregnancy, with particular risk in women with Marfan syndrome or other connective tissue disorders. 1

Acute Coronary Events

Coronary artery disease now represents 24% of cardiac deaths during pregnancy, including spontaneous coronary artery dissection (SCAD) which affects predominantly young women without traditional risk factors. 1

• SCAD occurs in up to 4% of all acute coronary syndromes but represents 20-35% of cases in women under 60 years of age. 2
• Pregnancy-related hormonal changes alter collagen structure in vessel walls, increasing vulnerability to dissection, with events occurring more frequently in the peripartum period. 2
• Myocardial infarction can occur through SCAD or atherosclerotic disease, particularly in older pregnant women or those with cardiovascular risk factors. 1

Heart Failure and Cardiomyopathy

Peripartum cardiomyopathy (PPCM) is the most common cause of severe cardiac complications in pregnancy, with myocardial disease/cardiomyopathy accounting for 27% of cardiac deaths. 1

• Pre-existing dilated cardiomyopathy can decompensate during pregnancy due to the hemodynamic burden, though women generally have better prognosis than men. 1
• Up to 25% of patients with familial dilated cardiomyopathy carry truncating variants in the titin gene, which predisposes to decompensation with pregnancy's "second hit" stress. 1
• Right heart failure can develop in women with congenital heart disease, particularly those with right ventricular outflow tract obstruction or repaired tetralogy of Fallot. 1

Arrhythmic Complications

Sudden arrhythmic cardiac death with morphologically normal hearts accounts for 18% of cardiac deaths in pregnancy, with arrhythmia incidence increasing to 80% in women with pre-existing congenital heart disease. 1

• Supraventricular arrhythmias occur in 10-60% of congenital heart disease cases outside pregnancy, rising dramatically during gestation. 1
• Atrial arrhythmias commonly develop or worsen in women with Fontan procedures, congenitally corrected transposition, or right-sided volume/pressure overload. 1
• Ventricular arrhythmias pose particular risk in women with hypertrophic cardiomyopathy, though women have fewer arrhythmic complications than men. 1

Valvular Heart Disease Complications

Women with mitral stenosis are at particularly high risk because the stenotic valve cannot accommodate increased cardiac output, causing sharp rises in transvalvular gradient and left atrial pressure, precipitating pulmonary edema. 3, 4

• Heart failure in mitral stenosis typically manifests between the third and fifth months when cardiac output increases are maximal. 4
• Severe symptomatic mitral or aortic stenosis may contraindicate pregnancy, with mortality ranging 0-3% but significantly higher morbidity. 4, 3
• Tricuspid regurgitation can develop or worsen during pregnancy in women with right-sided lesions. 1

Thromboembolic Complications

Pregnancy creates a hypercoagulable state with highest risk for pulmonary embolism occurring immediately postpartum (incidence 0.1-0.67 per 1000 pregnancies), and venous thromboembolism caused 34 maternal deaths in the 2015-2017 UK reporting period. 1

• Right atrial thrombus formation can occur in Fontan patients with risk of paradoxical embolism if fenestrated. 1
• Stroke risk increases throughout pregnancy due to hypercoagulability and hemodynamic changes. 1

Obstetric Complications in Women with Cardiac Disease

Women with cardiovascular disease face increased risk of pre-eclampsia, pre-term delivery, and postpartum hemorrhage. 1

• In one study of 79 women with chronic coronary disease, 66% had adverse cardiac events, 14% developed pre-eclampsia, 25% delivered preterm, and 25% had infants small for gestational age. 1
• Spontaneous abortion occurs in up to 40% of pregnancies in women with Fontan procedures, likely due to venous congestion. 1

Critical Timing of Complications

Peak Risk Periods

The hemodynamic burden peaks at 24-32 weeks gestation when cardiac output reaches maximum (40-50% above baseline), placing greatest stress on the cardiovascular system. 1, 4

• Labor represents an additional critical period, with cardiac output rising further as uterine contractions cause autotransfusion of 300-500 ml blood back to circulation. 1
• The postpartum period (first 24-48 hours) represents a second critical high-risk window with significant hemodynamic shifts. 3
• Immediate postpartum carries highest risk for pulmonary embolism. 1

Hemodynamic Mechanisms Underlying Complications

The physiological changes driving these complications include:

• Plasma volume increases 40% by 24 weeks gestation, creating volume overload in women with limited cardiac reserve. 1
• Cardiac output increases 30-50%, primarily through increased stroke volume early in pregnancy and heart rate elevation later. 1
• Systemic vascular resistance falls due to peripheral vasodilation, which increases right-to-left shunting in cyanotic heart disease. 1
• Heart rate increases 10-20 bpm, particularly in the third trimester, reducing diastolic filling time in stenotic lesions. 1

Risk Stratification

Women with NYHA class III or IV functional status are at highest risk regardless of underlying condition, as this indicates no remaining cardiovascular reserve. 1

• The CARPREG II risk score should be used for risk stratification, with history of chronic coronary disease independently associated with adverse cardiac events (odds ratio 3.0). 1
• Modified WHO class 4 conditions generally contraindicate pregnancy, while class 3 requires careful multidisciplinary evaluation. 1

Common Diagnostic Pitfalls

Rheumatic heart disease is now rare in Western countries except in immigrants, and shortness of breath may be wrongly attributed to normal pregnancy or asthma rather than mitral stenosis, causing dangerous delays in diagnosis. 3

• Normal pregnancy causes physiological changes that can mimic cardiac disease: heart rate increases 10-20 bpm, blood pressure decreases 10-15 mmHg by 20 weeks, and mild dyspnea on exertion is common. 1
• However, BNP and troponin are NOT elevated in normal pregnancy—elevation indicates true pathology such as pre-eclampsia, pulmonary embolism, myocarditis, or heart failure. 1
• Respiratory rate remains unaltered in normal pregnancy; if >20 breaths per minute, consider pathological causes. 1