What is the risk of worsening ischemic heart disease during pregnancy and how should a woman of child‑bearing age with known IHD be counseled and managed before, during, and after pregnancy?

Risk of Ischemic Heart Disease Worsening in Pregnancy

Women with pre-existing ischemic heart disease face a 9% risk of major ischemic complications during pregnancy (including death, acute coronary syndrome, and ventricular tachycardia), with only 21% experiencing completely uncomplicated pregnancies, and those with atherosclerotic coronary artery disease face the highest cardiovascular complication rate at 50%. 1

Maternal Mortality and Major Cardiac Risks

• Maternal mortality in women with pre-existing IHD is 2%, with deaths occurring both during pregnancy and postpartum 1
• Coronary artery disease accounts for 24% of all cardiac deaths during pregnancy 2
• Women with atherosclerotic disease have significantly more cardiovascular complications (50%) compared to those with other IHD etiologies (23%), though ischemic event rates are similar 1
• The overall incidence of pregnancy-associated myocardial infarction ranges from 1.5-10 per 100,000 deliveries, with an inpatient mortality rate of 5-7% 3

Risk Stratification Using Modified WHO Classification

All women with known IHD should be classified using the modified WHO maternal cardiovascular risk system before conception 4:

• WHO Class III (19-27% maternal risk): Moderate left ventricular impairment requires frequent cardiology and obstetric review 4
• WHO Class IV (40-100% maternal risk, pregnancy contraindicated): Severe systemic ventricular dysfunction (LVEF <30%) or NYHA class III-IV symptoms 5, 4
• History of chronic coronary disease independently increases adverse cardiac events (odds ratio 3.0) 2

Mechanisms of Deterioration During Pregnancy

The hemodynamic burden creates multiple pathways for IHD worsening 5, 2:

• Plasma volume increases 40% by 24 weeks gestation, creating volume overload in women with limited cardiac reserve 2
• Cardiac output increases 30-50%, peaking at 24-32 weeks when cardiovascular stress is maximal 5, 2
• Heart rate rises by 10-20 beats/minute, increasing myocardial oxygen demand 5
• Pregnancy creates a hypercoagulable state, increasing thrombotic risk in atherosclerotic vessels 2
• Hormonal changes may directly worsen coronary pathophysiology beyond hemodynamic effects 5

Critical Timing of Complications

• Greatest hemodynamic stress occurs at 24-32 weeks gestation when cardiac output reaches maximum 2
• Labor causes further acute increases in cardiac output with each uterine contraction 5
• Immediately postpartum represents the highest risk period due to massive autotransfusion of 500-1000 mL from uterine decompression and vena cava decompression 5, 6
• Hemodynamic changes regress by approximately 6 weeks postpartum 5

Pre-Pregnancy Counseling Requirements

All women of childbearing age with IHD require formal pre-conception counseling by a cardiologist with pregnancy expertise 5, 4:

• Assess current functional status (NYHA classification) - any woman in NYHA class III or IV has high risk regardless of underlying condition 5, 2
• Evaluate left ventricular function via echocardiography - LVEF <30% is an absolute contraindication to pregnancy 5, 4
• Identify teratogenic medications requiring substitution (ACE inhibitors, ARBs, statins) before conception 5
• Discuss 21% probability of uncomplicated pregnancy versus 9% risk of major ischemic events 1
• Women with atherosclerotic coronary disease should be counseled about their 50% cardiovascular complication rate 1

Management During Pregnancy

A multidisciplinary pregnancy heart team including ACHD/cardiology, maternal-fetal medicine, and anesthesiology must manage all women with IHD at a specialized center 5, 4:

• Cardiology follow-up every trimester minimum for WHO Class II-III risk 4
• Continuous ECG, invasive arterial blood pressure monitoring, and pulse oximetry during labor and delivery 6
• Avoid Valsalva maneuvers during second-stage labor; use assisted delivery (forceps/vacuum) to prevent sudden increases in intrathoracic pressure 6
• Continue intensive hemodynamic monitoring for at least 24 hours postpartum to detect delayed heart failure from autotransfusion 6

Anesthetic Considerations

For women with preserved ventricular function (NYHA I-II), carefully titrated epidural anesthesia is preferred 6:

• Provides gradual sympathetic blockade and preserves cardiac output 6
• Single-shot spinal anesthesia must be avoided as abrupt sympathetic blockade causes catastrophic hypotension in patients with fixed cardiac output 6

For severe ventricular dysfunction, general anesthesia may be required 6

Medication Management

• Aspirin should be continued throughout pregnancy - emerging evidence shows it prevents preeclampsia, preterm labor, and reduces maternal mortality 3
• Beta-blockers, calcium channel blockers, and nitrates can be continued with appropriate fetal monitoring 3
• Discontinue ACE inhibitors, ARBs, and statins before conception due to teratogenicity 5

Obstetric and Fetal Complications

Beyond maternal cardiac risks, women with IHD face 1:

• Obstetric complications in 58% of pregnancies (preeclampsia, preterm labor, postpartum hemorrhage) 1
• Fetal/neonatal complications in 42% (prematurity, low birth weight, increased congenital heart disease transmission) 1

Critical Pitfalls to Avoid

• Do not use methylergonovine for postpartum hemorrhage - causes marked vasoconstriction and hypertension, risking heart failure or coronary ischemia; use slow IV oxytocin (<2 U/min) instead 6
• Do not underestimate postpartum risk - the 500-1000 mL autotransfusion can overwhelm a compromised heart within 12-24 hours after delivery 6
• Do not provide aggressive fluid loading before epidural in women with ventricular dysfunction, as this precipitates pulmonary edema 6
• Only 22% of women who died from cardiac causes had known pre-existing cardiac disease, emphasizing need for vigilance even in apparently lower-risk patients 4

Absolute Contraindications to Pregnancy

Pregnancy should be avoided or terminated in 5, 4:

• Severe systemic ventricular dysfunction (LVEF <30%)
• NYHA class III-IV symptoms
• Pulmonary arterial hypertension (30-50% maternal mortality)
• Previous peripartum cardiomyopathy with residual impairment