What is the role of the TAP (Transannular Patch) technique in surgical repair of Tetralogy of Fallot (TOF)?

The Role of Transannular Patch (TAP) Technique in Tetralogy of Fallot Repair

The transannular patch (TAP) technique is a surgical approach used in Tetralogy of Fallot repair when the pulmonary annulus is hypoplastic, but it should be avoided whenever possible due to its association with long-term pulmonary regurgitation and increased need for future pulmonary valve replacement.

Anatomical Context and Surgical Decision-Making

Tetralogy of Fallot (TOF) is characterized by four components:

• Subpulmonary infundibular stenosis
• Ventricular septal defect (VSD)
• Aortic override of the VSD (<50% of diameter)
• Right ventricular hypertrophy

The surgical repair of TOF requires:

1. VSD closure
2. Relief of right ventricular outflow tract (RVOT) obstruction

When TAP Is Used

A transannular patch is employed when:

• The pulmonary annulus is significantly hypoplastic (typically Z-score < -2)
• Simple resection of infundibular stenosis is insufficient
• Pulmonary valvotomy alone cannot relieve obstruction

Consequences of TAP Technique

Immediate Benefits

• Effectively relieves RVOT obstruction
• Provides adequate pulmonary blood flow
• Allows for complete repair in a single operation

Long-Term Complications

• Severe pulmonary regurgitation (PR) in nearly all cases 1
• Right ventricular dilation and dysfunction 1
• Increased risk of arrhythmias
• Decreased exercise capacity 1
• Need for pulmonary valve replacement (PVR) later in life 2, 3

Evidence Supporting Pulmonary Annulus Preservation

Recent studies strongly favor pulmonary annulus preservation over TAP:

• Patients with annulus-preserving repairs have significantly higher 30-year survival (99.1% vs 90.4%) compared to TAP 3
• TAP patients are nearly 6 times more likely to require pulmonary valve replacement (PVR) 4
• Freedom from PVR at 15 years postoperative was 100% in annulus-preserving group vs 74% in TAP group 2
• Even with moderate residual pulmonary stenosis, valve-sparing procedures result in fewer cardiovascular interventions than TAP 3

Modern Surgical Alternatives to TAP

1. Pulmonary valve leaflet plasty techniques:

   • Bicuspid pulmonary leaflet plasty
   • Leaflet augmentation
   • Achieved 95% freedom from TAP in one study 5

2. Monocusp reconstruction with TAP:

   • When TAP is unavoidable, adding a monocusp valve prolongs the interval before severe PR develops (6.5 vs 3.8 years) 6

3. Pulmonary valve-sparing techniques:

   • Infundibular muscle resection
   • Pulmonary valvotomy
   • Supravalvar patching

Follow-up Considerations After TAP

Patients with TAP require:

• Annual follow-up with ACHD cardiologist 1
• Regular cardiac MRI to assess RV volume and function 1
• Monitoring for PR, RV dilation, and dysfunction
• Evaluation for PVR when symptoms develop or for RV preservation 1

Indications for Pulmonary Valve Replacement After TAP

PVR is recommended for patients with:

1. Moderate or greater PR with cardiovascular symptoms 1
2. Asymptomatic patients with RV enlargement or dysfunction 1
3. Sustained tachyarrhythmias
4. Progressive reduction in exercise tolerance

Conclusion

While the TAP technique effectively relieves RVOT obstruction in TOF repair, it creates inevitable pulmonary regurgitation that leads to long-term complications. Modern surgical approaches strongly favor pulmonary annulus preservation whenever possible, even accepting mild to moderate residual stenosis, as this significantly improves long-term outcomes and reduces the need for future interventions.