LBBAP implant procedure
LBBAP was attempted with two different combinations of pacing leads and delivery sheaths. In the first group, LBBAP was performed with a 4.1 Fr thin lumen-less pacing lead (LLL group) with a fixed helix design (SelectSecure 3830 pacing lead, Medtronic Inc, Minnaepolis, MN, USA) delivered through a long preshaped sheath (C315His, Medtronic) (Figure 1, panel A). In the comparator group, LBBAP was performed with a 5.6 Fr stylet-driven pacing lead with an extendable helix (Solia S60, Biotronik, SE & Co, KG, Berlin, Germany) delivered through a preshaped sheath (Selectra 3D, Biotronik) (Figure 1, panel B). This sheath became available in a prelimited market release with three different curves depending on the width of the primary curve (40, 55 or 65mm).
The SelectSecure 3830 lead requires no additional lead preparation and the lead was directly advanced through the C315His delivery sheath. The Solia S lead was prepared by exposing the extendable screw by turning the outer pin 5-10 times clockwise. After complete exposure of the 1,8 mm extendable helix, tension on the inner coil was applied by clockwise turning the outer pin an additional 8 times using the standard stylet guide tool delivered with the lead (Figure1 panel B).15 This manoeuver helps to avoid partial unwinding of the extendable helix, as manual rotations applied on the outer body of the lead could cause the inner coil not to follow the outer lead body rotations15.
LBBAP was subsequently performed as described previously by Huang et al.4, 7 In brief, the His bundle region was mapped with the pacing lead in unipolar configuration and used as fluoroscopic reference. The pacing lead and sheath were than advanced 1-2cm towards the apex in the right anterior oblique view with a slight counterclockwise rotation to guide the pacing lead towards the septum. Perpendicular position to the septum was assessed in the left anterior oblique view by injecting a small amount of contrast through the delivery sheath to delineate the septum. At this point, pace mapping with unipolar pacing at the tip of the lead was performed to assess the presence of a wide “W” shaped QRS morphology in lead V1 of the 12-lead surface electrocardiogram (ECG). Both LLL and SDL were advanced with manual rotations applied on the outer lead body. For the SDL, the stylet was fully advanced to the tip of the pacing lead during screwing in of the lead. Manual rotations were applied with the use of a third hand, while the first operator fixated the sheath against the septum. As the pacing lead advanced into the septum, the “W” shaped QRS morphology in lead V1 gradually changed to incomplete right bundle branch block morphology with continuous monitoring of the unipolar lead impedance and fluoroscopic advancement of the lead into the septum. Successful LBBAP was defined by the appearance of an incomplete right bundle branch block morphology in lead V1 and a shortened stimulus to peak left ventricular activation time (LVAT) among leads V5-V6, which remained constant and short at both low and high output pacing.6, 7, 16intracardiac recordings on the tip of the pacing lead were assessed for a discrete left bundle branch potential (LBBp) with the use of an electrophysiology recording system (BARD Labsystem, C.R Bard Inc, Lowell, MA, USA). Final lead implant depth and confirmation of the lead position towards the left side of the septum were assessed by injecting a small amount of contrast though the delivery catheter (Figure 2). Perforation of the septum during implant was defined as sudden decrease in pacing impedance of > 200 ohms, high unipolar pacing thresholds > 3V and leakage of contrast into the left ventricle.