Procedure description
Once vascular access is obtained, a guidewire is advanced into the right
atrium (RA) or right ventricle (RV). A short 10.5F sheath is advanced
over the wire to retain access. The EIS catheter is prepared normally.
With the dilator inserted, the EIS catheter shaft can then be shaped for
LBBP. The distal end of the EIS catheter, when maximally deflected forms
two 90° deflections. The distance between the first deflection to the
second 90° deflection is approximately 40.5±6.0 mm. While this distance
has proved adequate for reaching the His bundle, it is too short for
crossing the tricuspid valve and reaching the RV septum. Reshaping the
EIS catheter proximal to the second deflection would extend our reach
beyond the tricuspid valve, and in close proximity to our intended
septal target. The further addition of a septal curve would allow us to
maintain a perpendicular catheter orientation to the RV septum (Figure
1). The distal 25 mm of the IS-1 pacing lead (Tendril STS Model 2088TC)
is stiff and non-deflectable, the septal curve can only be effective
proximal to this point. Any attempts at introducing the septal curve in
the distal 25 mm of the catheter would inevitably result in
straightening of the shaped septal curve when the lead is introduced.
Shaping the septal curve should thus be performed only between the first
and second deflection of the EIS catheter, as this point falls between 3
- 7 cm of the lead tip when the lead is fully inserted.
Using a 0.035-inch guidewire, the entire assembly comprising the
reshaped dilator and EIS catheter is advanced into the RA. The
introducer and guidewire are then removed, followed by the introduction
of a 58cm IS-1 pacing lead, which is advanced to the tip of the sheath.
At this point, the distal tip of the lead need not be exposed beyond the
sheath as the EIS catheter allows for both mapping and pacing via the
distal platinum iridium electrodes.
The EIS catheter is connected to Merlin pacing system analyzer (PSA),
and an electrophysiology recording system via the supreme
electrophysiology cable and the use of stacked wires. The lead can also
be connected in a unipolar fashion using threshold cables and stacked
wires. The His bundle location can be mapped by using the EIS catheter
and an X-Ray reference image set. Care should be taken during
manipulation of the catheter in the RA, and inadvertent coronary sinus
cannulation avoided by paying close attention to electrographic signals
from the EIS catheter as well as fluoroscopic images.
The initial site for LBBP is approximately 1 to 1.5 cm distal to the His
bundle location, in the RV septum along the line between the His bundle
site and the RV apex in the right anterior oblique (30°) view. Advancing
the reshaped catheter and with slight un-deflection would allow us to
reach this area. Gentle counterclockwise rotation, and with the aid of
the reshaped septal curve, a perpendicular septal orientation can be
obtained (Figure 2).
The exact orientation of the EIS catheter to the septum should be
determined in the left anterior oblique (30°) view. A more perpendicular
septal orientation can be achieved by further un-deflecting and
retracting the catheter, while maintaining gentle counterclockwise
torque of the catheter. Pacing using the EIS catheter is then performed
before lead fixation, with the aim of demonstrating a “w” pattern with
a notch at the nadir of the QRS in lead V1, and discordant QRS
morphology in the inferior leads (R in II taller than III), and in leads
aVR/aVL (negative in aVR, positive in aVL, Figure 3A). The lead is
advanced slightly beyond the sheath, and the helix extended. Unipolar
pacing can be performed at this stage, and the pacing impedance
documented.
Penetration of the lead into the septum can be achieved by rotation of
the lead body. Unique to the EIS catheter, there are two specific points
of resistance for effective transmission of torque to the lead tip; (1)
the resistance incurred at the hemostasis valve on the lead body, which
can be overcome with the insertion of the bypass tool (Figure 4A).
Gentle forward pressure on the lead is required once the bypass tool is
inserted to maintain pressure of the lead tip against the septum, (2)
the two 90° deflection points can create resistance as well, especially
when the stylet is fully inserted. This can be overcome by retracting
the stylet proximal to both deflections (~9 to 10 cm,
Figure 4B). The IS-1 pacing lead, with support from the sheath, has
enough stiffness to allow for forward pressure to be applied and
effective septal penetration without the need of a fully inserted stylet
for support.
Clockwise rotation of the lead can be applied 3-4 turns at a time. The
helix will inadvertently be retracted when the lead body is rotated
clockwise (which can be confirmed with fluoroscopy). This can be
overcome by re-extending the helix using the clip-on tool. Failure to
re-extend the helix at this stage would lead to inadvertent lead
dislodgement (Figure 5). The maneuver of lead body rotation and helix
re-extension is repeated until the desired depth is achieved, and left
bundle capture can be confirmed using previously described pacing
techniques6 (Figure 3).
If perforation of the LV occurs, the lead should be withdrawn and
repositioned. Withdrawing the lead should be done with counterclockwise
rotation of the lead body while the helix is still extended. Retracting
the helix prior to withdrawing of the lead body from the septum would
entrap the helix in an extended position. The helix should be retracted
only when the lead is fully withdrawn into the sheath.
Once the lead is in position, the catheter can be removed. The lead with
the stylet still retracted is advanced to allow for adequate slack,
while un-deflecting and retracting the sheath. The slitter tool has a
unique lead stabilization channel that cups the lead and engages the
shaft of the sheath. The slitter tool with the cupped lead can then be
advanced into the hemostasis valve before engaging the lead into the
lead retention channel on the slitter tool. The rest of the lead can
then be guided into the thumbpad groove and secured with your thumb. The
shaft of the catheter is aligned to the slitter tool reference line, and
the catheter slit with a smooth axial motion.