What organ anomalies are thoracophagus (conjoined) twins most likely to have?

Thoracopagus Twins Most Commonly Have Cardiac Anomalies

Thoracopagus conjoined twins most commonly have cardiac anomalies, with shared or complex heart defects being the predominant organ abnormality in this type of conjoined twinning.

Understanding Thoracopagus Twins

Thoracopagus twins are a type of conjoined twins that are connected at the thorax (chest). According to current medical guidelines, they represent the most extreme example of late separation of monozygotic twins, occurring when splitting happens after 13 days post-fertilization 1.

Cardiac Anomalies in Thoracopagus Twins

The evidence strongly indicates that cardiac abnormalities are the most significant and common organ anomalies in thoracopagus twins:

• Cardiac union is present in the majority of thoracopagus twins, with approximately 90% having complex cardiac connections that make surgical separation extremely challenging 2
• These cardiac anomalies typically include:
  • Shared atrium (common atrium)
  • Connected ventricles
  • Complex outflow tract abnormalities
  • Abnormal great vessel arrangements 3, 2

The complexity of cardiac anomalies in thoracopagus twins is highlighted by findings such as:

• Six-chambered hearts 3
• Isomerism of atrial appendages 4
• Atrioventricular septal defects 4
• Aortic abnormalities 5

Surgical Implications and Outcomes

The presence of cardiac anomalies significantly impacts the prognosis and surgical separability of thoracopagus twins:

• Only about 10% of thoracopagus twins with cardiac connections are suitable candidates for surgical separation 2
• Survival rates after separation vary dramatically based on the extent of cardiac connection:
  • Type A (completely separate hearts): 70% survival
  • Type B (atrial connection only): 10% survival
  • Type C (both atrial and ventricular connections): 0% survival 6

Other Associated Anomalies

While cardiac anomalies predominate, thoracopagus twins may also have other organ involvement:

• Conjoined liver is commonly seen 2, 5, 6
• Shared gastrointestinal tract components may be present 5
• Other anomalies may include cleft lip/palate and splenic abnormalities 5

Diagnostic Approach

For thoracopagus twins, comprehensive cardiac evaluation is essential:

• Fetal echocardiography should be performed as the risk of cardiac anomalies is significantly elevated 1
• MRI with contrast-enhanced magnetic resonance angiography (MRA) provides detailed evaluation of extra-cardiac anatomy 3
• Serial ultrasound monitoring is necessary to assess for other complications 1

Clinical Implications

The high prevalence of cardiac anomalies in thoracopagus twins has significant implications for:

• Prenatal counseling regarding prognosis
• Delivery planning
• Potential for surgical separation
• Overall survival expectations

The mortality and morbidity associated with thoracopagus twins is primarily driven by the complexity of their cardiac anomalies, making cardiac assessment the most critical component of their evaluation and management.