What is the significance of an extra cardiac structure on a fetal (fetal) echocardiogram?

Significance of Extra Cardiac Structures on Fetal Echocardiography

Extra cardiac structures on fetal echocardiography may indicate significant congenital anomalies that can impact fetal and neonatal outcomes, requiring prompt evaluation and multidisciplinary management. 1

Types of Extra Cardiac Structures and Their Significance

Congenital Anomalies

• Extra cardiac structures may represent congenital anomalies such as diaphragmatic hernia, lung masses, or other structural defects that can affect cardiac function and hemodynamics 1
• These anomalies are often associated with chromosomal abnormalities, with studies showing abnormal chromosomes in up to 38% of fetuses with cardiac structural anomalies 2

Twin Pregnancy Complications

• In monochorionic twin pregnancies, extra cardiac structures may indicate complications such as Twin-Twin Transfusion Syndrome (TTTS) or Twin Reversed Arterial Perfusion (TRAP) sequence 1
• Velamentous placental cord insertion has been found in approximately one-third of placentas with TTTS and may appear as an extra structure on fetal echocardiography 1

Vascular Anomalies

• Extra vascular structures may represent abnormal vascular connections or malformations that can affect cardiac loading conditions 1
• These include placental chorioangioma, vein of Galen aneurysm, or absent ductus venosus, which can lead to high-cardiac output states and potential hydrops 1

Clinical Implications and Management

Diagnostic Evaluation

• When an extra cardiac structure is identified, a comprehensive assessment should be performed to determine its nature and potential impact on cardiac function 1
• This includes evaluation of:
  • Cardiac size (normal cardiothoracic ratio using area is 0.25 to 0.35) 1
  • Ventricular function (normal fractional shortening >28%) 1
  • Presence of valvular regurgitation 1
  • Doppler flow patterns in major vessels 1

Risk Assessment

• The presence of extra cardiac structures may indicate increased risk for:
  • Congenital heart disease (9-fold increase in monochorionic twins, up to 14-fold in TTTS) 1
  • Hemodynamic compromise leading to hydrops fetalis 1
  • Postnatal complications requiring immediate intervention 1

Monitoring and Follow-up

• Serial fetal echocardiography is recommended to monitor:
  • Progression of cardiac function using the Cardiovascular Profile Score (CVPS) or Myocardial Performance Index (MPI) 1
  • Development of hydrops or other signs of cardiac decompensation 1
  • Response to any intrauterine interventions 1

Multidisciplinary Approach

• Management of pregnancies with extra cardiac structures on fetal echocardiography requires a multidisciplinary team including:
  • Pediatric cardiology 1
  • Maternal-fetal medicine 1
  • Genetics 1
  • Neonatology 1
  • Pediatric cardiac surgery 1

Prognostic Implications

• Early detection of extra cardiac structures through fetal echocardiography allows for:
  • Improved prenatal counseling regarding expected outcomes 3
  • Appropriate planning for delivery at centers with specialized neonatal care 1
  • Preparation for potential immediate postnatal interventions 1, 3
  • Better overall outcomes for selected fetuses with severe cardiac or extracardiac anomalies 3

Pitfalls and Caveats

• Not all extra cardiac structures represent pathology; some may be normal variants or temporary findings 4
• The accuracy of fetal echocardiography depends on:
  • Gestational age (optimal imaging at 18-22 weeks) 1
  • Maternal factors (body habitus, position) 1
  • Fetal position 1
  • Expertise of the examiner 1
• Some cardiac defects may evolve during gestation and may not be apparent on early fetal echocardiography 1, 4
• Maintain a high level of suspicion for cardiac defects regardless of fetal echocardiography findings, as some lesions are difficult to diagnose prenatally 4