Discussion.
Our experience with the EIS catheter demonstrated its feasibility as a
delivery system for LBBP. The catheter was originally designed as an
effective delivery system for HBP, but with several simple but crucial
modifying steps, it can be effectively adopted for LBBP:
- Reshaping the catheter to allow for an extended reach and a septal
curve.
- The use of the bypass tool and retracting the stylet to allow for
adequate transmission of torque to the lead tip.
- Close attention to helix retraction during lead body rotation, and
re-extension of the helix as necessary.
Failure to perform LBBP occurred in 3 patients, predominantly in the
early phase of adopting the catheter for LBBP. The lessons learnt during
these failed attempts, as well as lessons from porcine in vitro
experiments, allowed us to formulate steps to overcome the inherent
pitfalls of this catheter:
- Without reshaping the catheter, it would not have enough reach to
cross the tricuspid valve and arrive at the RV target septal area for
LBBP. Without the addition of a septal curve, the sheath and the lead
would have an oblique orientation to the RV septum, resulting in a
longer (obliquely and superiorly directed) transseptal track to the
LBB area. The majority of the failed attempts occurred because the
catheter simply could not reach the target area, and if it could, the
oblique trajectory resulted in poor pacing outcomes (LV septal
pacing).
- Without the bypass tool and retracting the stylet, application of
torque on the lead body would result in lead spiraling and insulation
wrinkling, without further penetration of the septum, as torque is not
transmitted to the lead tip.
- Helix retraction during lead body rotation would result in lead
dislodgement, often at the time of septal penetration. By re-deploying
the helix, we can avoid dislodgements.
- Repositioning of the lead, if required, should be performed by first
rotating the lead body with the helix still extended. Attempts at
retracting the helix with the lead buried deep in the septum would
result in entrapment of myocardial tissue in the helix, damaging the
lead tip, or trapping the lead tip in the septum, or both.