Which repair has the greatest risk of heart block?

• A. ASD repair
• B. VSD repair
• C. PDA ligation
• D. Tetralogy of Fallot repair

Answer: (B)

Conduction system injury risk rises when the surgical repair is right next to the heart’s electrical pathways. The membranous part of the interventricular septum sits very close to the AV node and His bundle. When repairing a VSD in this region, sutures or patch placement can directly affect those conduction tissues, making complete heart block a relatively likely complication compared with other repairs.

In ASD repairs, the operative area is further from the main conduction axis, so the chance of injuring the AV node or bundle is lower. PDA ligation targets a vessel away from the conduction system, carrying minimal risk of heart block. Tetralogy of Fallot repair can involve the right ventricular outflow tract and infundibulum, which may affect nearby conduction tissue but not as directly or frequently as involvement of the membranous septum during VSD repair. Hence, the repair with the greatest risk of heart block is the VSD repair.