[Implantation]
The left axillary vein was punctured to obtain venous access, an
incision was made 4 cm below the left clavicle to make a capsular bag.
the C315 HIS sheath was advanced over a long guide-wire towards the
tricuspid annulus, the 3830 lead was then advanced to the tip of the
sheath towards His bundle region,
HB region was mapped in the
unipolar configuration. His potential can be detected[Fig1①] , His lead was fixed by sightly screw followed by
HBP, however HBP showed a unsatisfactory sensing, a high and unstable
capture threshold, then His lead was used as a protective lead in case
of temporary pacing, and the X-ray reference image of location of His
lead was routinely regard as a marker for LBBP lead implantation.
Another 3830 lead was advanced to tip of the sheath towards surface of
right ventricular septum, the initial site for LBBP, was approximately
1cm distal to the HBP lead position on the surface of right ventricular
septum along the line between HBP site and right ventricular apex in the
fluoroscopy view of right anterior oblique (RAO 30°)[Fig1④] , At this site, the paced QRS complex morphology
usually demonstrates a “w” pattern with a notch at the nadir of the
QRS in lead V1 [Fig1②][5] .
Then, the sheath was rotated anticlockwise to maintain the orientation
of lead tip perpendicular to septal surface and provide adequate support
to screw the lead into the septum. As lead tip screwing into
inter-ventricular septum, lead parameters (R wave sensing and LBB
capture morphologies and thresholds) were assessed synchronously in both
unipolar and bipolar configurations. The following signs will appear: 1)
the notch of paced QRS complex in lead V1 will move from nadir to the
end [Fig1③] . 2) First increase then reduction of pacing
impedance in unipolar. 3) the position of lead tip advances with fulcrum
sign left behind on fluoroscopy [Fig1④] .
The lead tip advanced cautiously until satisfactory parameters were
achieved, the latter included lead tip impedance 560Ω, ring impedance
650Ω, bipolar impedance 735Ω, threshold 0.7V, QRS amplitude 28.5mV, left
branch bundle potential cannot be detected during the procedure.
The right ventricular defibrillation lead 6947 was implanted in right
ventricle (RV) apex in a standard fashion (rotation, fixation et al.).
Parameters of RV lead were identified with threshold 0.7v, the QRS
amplitude 5.4mV, and impedance 399Ω.
The system (C315 HIS sheath and 3830 lead) located in His bundle region
was then withdrawn to inferior right atrial septum. Parameters of right
atrial lead were assessed with threshold 0.4V, P amplitude 2.7mV, and
impedance 574Ω.