Incision of the Moderator Band During Repair of Tetralogy of Fallot

Objective 

Whether the moderator band should always be preserved or cut during the relief of the pulmonary subvalvar obstruction in the repair of tetralogy of Fallot (TOF) is a controversial topic. This presentation includes two cases illustrating that, at times, the moderator band can obstruct the right ventricular outflow tract in TOF and should be incised.  

The first case involved a patient with a previous history of TOF, who underwent TOF repair at three months of age, followed by reoperation for recurrent right ventricular outflow tract obstruction at three years of age. At nine years, this patient experienced recurrent right ventricular outflow tract obstruction with a peak gradient of 108 mm Hg. The second patient had a previous history of TOF and underwent elective TOF repair at four months of age. 

Case Video Summary 

The first case in the video demonstrates that the moderator band serves as the substrate creating right ventricular obstruction. Although the subvalvar apparatus of the anterior leaflet is attached to it, the moderator band needed to be resected. The second case depicted a patient with the exact same anatomy. An elective incision of the moderator band was performed to avoid residual right ventricular outflow tract obstruction. 

Conclusions 

In some instances, the moderator band is the source of subpulmonary obstruction in TOF and must be incised during repair, even when the tricuspid subvalvar apparatus is attached to the moderator band. 

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