What conditions make a hybrid procedure preferable to a Norwood procedure?

Conditions Favoring Hybrid Procedure Over Norwood Procedure

The hybrid procedure is strongly preferred over the Norwood procedure for hypoplastic left heart syndrome (HLHS) in high-risk patients with characteristics including low birth weight (<2.5 kg), prematurity (especially <35 weeks), severe ventricular dysfunction, and severe atrioventricular valve regurgitation. 1, 2

High-Risk Patient Characteristics

• Low birth weight (<2.5 kg) is a primary indication for hybrid approach as these infants have higher mortality with traditional Norwood procedures 1, 2
• Prematurity (especially <35 weeks gestation) increases surgical risk significantly, making hybrid approach more favorable 2, 3
• Central nervous system abnormalities may benefit from avoiding cardiopulmonary bypass in the neonatal period 1
• Multiorgan failure presents excessive risk for traditional Norwood surgery 1
• Intact or severely restrictive atrial septum is associated with poor outcomes regardless of approach but may have better initial survival with hybrid procedure 2, 4
• Severe ventricular dysfunction increases surgical risk substantially for Norwood procedure 1, 2
• Severe atrioventricular valve regurgitation complicates traditional surgical repair 1

Benefits of Hybrid Approach in High-Risk Patients

• Avoids cardiopulmonary bypass in the neonatal period, which is particularly beneficial for premature or low birth weight infants 5, 3
• Significantly lower rates of dialysis requirement compared to Norwood procedure (0% vs 19%) 4
• Reduced need for extracorporeal membrane oxygenation (ECMO) support (0% vs 22%) 4
• Better 30-day survival in high-risk patients (91% vs 66%) despite similar 1-year outcomes 4
• Combines surgical and interventional catheterization techniques including bilateral pulmonary artery bands, PDA stent implantation, and creation of unrestrictive atrial communication 5, 6

Contraindications to Hybrid Approach

• Retrograde aortic arch obstruction with fully open PDA is a contraindication due to potential acute obstruction to coronary flow 7
• Centers with limited hybrid procedure experience may have better outcomes with Norwood procedure even in higher-risk patients 1

Complications to Consider

• Higher rate of unplanned reinterventions with hybrid approach (43% vs 21%) 4
• Increased risk of necrotizing enterocolitis compared to Norwood procedure (53.3% vs 37.0%) 8
• Potential complications specific to hybrid approach include stent embolization, retrograde coarctation, proximal stenosis of uncovered ductus, and pulmonary artery distortion from banding 5, 6

Risk Stratification Approach

• Standard-risk patients generally have better outcomes with traditional Norwood procedure 1
• High-risk patients show improved early survival with hybrid approach despite similar midterm outcomes 4
• Intrinsic patient risk factors rather than treatment modality likely determine long-term outcomes in experienced centers 1

The decision between hybrid and Norwood procedures should be based primarily on patient risk factors, with hybrid approach offering better early survival for high-risk patients despite similar midterm outcomes. Centers should consider their institutional experience with both techniques when making this critical decision.