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.