What is the significance of a persistent left superior vena cava (PLSVC) in pediatric cardiac surgery?

Significance of Persistent Left Superior Vena Cava in Pediatric Cardiac Surgery

Persistent left superior vena cava (PLSVC) significantly increases mortality risk in children undergoing cardiac surgery and requires careful preoperative identification and surgical planning to avoid complications. 1

Definition and Prevalence

• PLSVC is defined as a congenital cardiovascular malformation in which there is a left superior vena cava, representing a systemic venous anomaly 2
• It is the most common thoracic venous anomaly, occurring in approximately 12.7% of children with congenital heart disease 1, 3
• In the general population without cardiac anomalies, the prevalence is much lower at approximately 0.3% 4

Anatomical Considerations

• PLSVC typically drains into the right atrium via the coronary sinus in most cases 5
• In a minority of cases, PLSVC may drain directly into the left atrium, creating a right-to-left shunt that can cause cyanosis and risk of paradoxical embolism 5, 3
• PLSVC is frequently associated with other cardiac anomalies that require surgical intervention 1

Clinical Significance in Pediatric Cardiac Surgery

Preoperative Considerations

• Preoperative identification is crucial - studies show that PLSVC is missed on preoperative echocardiography in approximately 17% of cases 1
• PLSVC is often associated with other congenital heart defects, increasing the complexity of surgical repair 2, 1
• Systemic venous anomalies including PLSVC should be carefully documented as part of standard cardiac evaluation 2

Intraoperative Challenges

• PLSVC can complicate cannulation for cardiopulmonary bypass 1
• Special surgical techniques may be required for venous drainage during cardiopulmonary bypass 1
• The dilated coronary sinus resulting from PLSVC drainage may interfere with access to other cardiac structures during surgery 1, 3

Associated Coronary Sinus Anomalies

• In approximately 17% of cases, PLSVC is associated with partially or completely unroofed coronary sinus 1
• Coronary sinus ostial atresia occurs in approximately 4% of PLSVC cases 1
• These associated anomalies can significantly complicate surgical repair and increase risk 1

Postoperative Complications

Hemodynamic Complications

• PLSVC can lead to significant inflow obstruction of the left ventricle after surgery in approximately 6.4% of cases 1
• This obstruction can cause low cardiac output syndrome or secondary pulmonary hypertension 1
• Patients with PLSVC require longer mechanical ventilation (median 3.0 days vs 1.2 days in controls) 1

Mortality Impact

• Mortality is significantly higher in children with PLSVC undergoing cardiac surgery (10.6% vs 2.5% in controls) 1
• This increased mortality risk makes preoperative identification and surgical planning critical 1

Management Considerations

Preoperative Imaging

• Comprehensive imaging is essential to identify PLSVC and associated anomalies 2
• Echocardiography is the first-line imaging modality but may miss PLSVC in some cases 1
• Cardiac MRI or CT should be considered for complete evaluation of complex venous anatomy 2

Surgical Planning

• Surgical approach must be modified based on the specific anatomy of the PLSVC and associated anomalies 1
• Special attention must be paid to the coronary sinus and its relationship to other cardiac structures 1, 3
• In single ventricle patients, PLSVC requires special consideration during staged palliation 2

Conclusion

The presence of PLSVC significantly impacts surgical approach, risk of complications, and mortality in pediatric cardiac surgery. Thorough preoperative identification and careful surgical planning are essential to mitigate these risks and improve outcomes.