Sheath Withdrawal May Represent a Mechanically Vulnerable Phase for Septal Perforation During Left Bundle Branch Area...

Although interventricular septal perforation is a recognized complication of left bundle branch area pacing (LBBAP), its underlying mechanisms remain unclear. Previous studies have focused primarily on lead deployment-related factors, whereas mechanical events occurring after apparently successful lead fixation have received limited attention.

In this exploratory mechanistic study, we investigated axial force transmission during delivery sheath withdrawal using a simplified benchtop model motivated by a representative clinical observation in which overt septal perforation became apparent immediately after sheath slitting. Axial force transmitted along the lead-sheath system was quantified under two geometric configurations simulating a constrained (5 cm) and less-constrained (10 cm) atrial space. Sheath withdrawal was performed in 1-cm increments under three initial orientations (neutral, clockwise, and counterclockwise). Peak axial force values were analyzed using two-way analysis of variance.

In the benchtop model, the constrained configuration generated significantly higher peak axial forces than the less-constrained configuration across all sheath orientations (p < 0.001). Initial sheath orientation significantly modified force transmission, with a counterclockwise orientation producing the highest peak axial force under constrained conditions (p < 0.001). Peak axial force consistently occurred during the early phase of sheath withdrawal, corresponding to a lead tip-to-sheath tip distance of approximately 3.5-4.5 cm. These mechanical findings were concordant with fluoroscopic observations from the index clinical case, in which distinct lead-tip excursion and overt septal perforation were recognized during early sheath withdrawal. However, subtle pre-existing protrusion of the lead helix before sheath withdrawal could not be excluded.

Sheath withdrawal during LBBAP may represent a mechanically vulnerable phase during which geometric constraint and sheath orientation can synergistically amplify axial force transmission to the lead tip. Recognition of this vulnerable phase, together with attention to atrial geometry and sheath orientation during early withdrawal, may help reduce the risk of lead destabilization or overt interventricular septal perforation during LBBAP.