Which repair carries the greatest risk of heart block?

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

Answer: (B)

The risk of heart block after congenital defect repair is highest when the surgery touches the heart’s conduction system, especially near the AV node and His bundle. A perimembranous VSD sits right next to these conduction pathways, so closing the defect often requires sutures very close to or over the conduction tissue. Injury here can disrupt AV conduction and lead to complete heart block, sometimes needing a pacemaker.

ASD repairs are typically performed in the fossa ovalis region, away from the main conduction pathways, so the chance of heart block is much lower. PDA ligation also avoids the conduction tissue, making block unlikely. Tetralogy of Fallot repair can affect conduction, particularly with certain patch techniques, but the risk of heart block is generally not as high as with a perimembranous VSD repair.

So, a VSD repair carries the greatest risk of heart block.