What are the considerations for cardiac catheterization in patients with Hypoplastic Left Heart Syndrome (HLHS)?

Cardiac Catheterization in Hypoplastic Left Heart Syndrome (HLHS)

Cardiac catheterization plays a critical role in the management of patients with Hypoplastic Left Heart Syndrome (HLHS), particularly for atrial septostomy to decompress the left atrium in cases with restrictive or intact atrial septum.

Diagnostic Indications

• Cardiac catheterization is reasonable to assess pulmonary arterial hypertension and test vasoreactivity in patients with HLHS, which is critical for surgical planning 1
• Hemodynamic assessment is indicated when noninvasive findings are equivocal or when evaluating pulmonary vascular resistance prior to staged palliation 1
• Cardiac catheterization is indicated in patients with complex cardiac anatomy when noninvasive imaging methods incompletely define pulmonary artery anatomy 1

Therapeutic Interventions

Atrial Septostomy

• Atrial septostomy is indicated for decompression of left atrial hypertension in HLHS with restrictive or intact atrial septum to improve oxygenation and clinical status before surgical palliation 1, 2
• Transcatheter left atrial decompression significantly reduces the transatrial gradient, decreases left atrial pressure, and improves oxygenation in HLHS patients with restrictive atrial septum 2
• Survival rates improve from approximately 10% with emergent Norwood to 57-73% with successful catheter-based left atrial decompression prior to surgery 2

Hybrid Procedures

• It is reasonable to perform hybrid stage I palliation (combining transcatheter and surgical techniques) in high-risk HLHS patients, including:
  • Right and left pulmonary artery banding
  • PDA stent implantation
  • Creation of an unrestrictive atrial communication 1
• This approach is particularly valuable for high-risk surgical candidates and as a bridge to heart transplantation 1
• Hybrid palliation may not be indicated in patients with significant retrograde aortic arch obstruction that might be compromised by PDA stent placement 1

Timing and Urgency

• Urgent/emergent catheterization is required for HLHS with intact or highly restrictive atrial septum, as this combination is highly lethal without prompt intervention 3
• Approximately 11% of newborns with HLHS require urgent catheterization to create or enlarge an interatrial communication before surgical palliation 3
• Early intervention is critical as HLHS with restrictive atrial septum presents with severe cyanosis, pulmonary edema, and critical illness 2

Potential Complications

• Major complications of atrial septostomy occur in approximately 10% of cases, including:
  • Atrial perforation requiring intervention
  • Balloon rupture and embolization
  • Failure of balloon deflation
  • Vascular injury (rare)
  • Embolic complications such as stroke 1
• The failure rate of transcatheter atrial septostomy requiring surgical septectomy is approximately 27% 2
• Complications of hybrid palliation include stent embolization, retrograde coarctation, proximal stenosis of uncovered ductus, and pulmonary artery distortion 1

Long-term Considerations

• Despite improved early survival with modern interventional and surgical techniques, HLHS patients continue to face significant morbidity and early mortality 4
• Adult HLHS patients face significant life-long morbidity from elevated systemic venous pressures as a consequence of the Fontan procedure 4
• Regular follow-up with cardiac catheterization may be needed to assess hemodynamics and pulmonary vascular resistance in the staged palliation process 1

Special Considerations

• Prenatal diagnosis allows for planned intervention immediately after birth, which may improve outcomes 5
• Fetal intervention is being developed for HLHS with intact atrial septum to promote normal pulmonary vascular and parenchymal development 3
• Careful monitoring for restenosis of the atrial septum is necessary following intervention 1
• The presence of a morphologic systemic right ventricle may place HLHS patients at even higher risk than other adult patients with a Fontan circulation 4

Cardiac catheterization remains an essential tool in the comprehensive management of HLHS, both for diagnostic assessment and life-saving interventions, particularly in the critical neonatal period.