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:
  1. Reshaping the catheter to allow for an extended reach and a septal curve.
  2. The use of the bypass tool and retracting the stylet to allow for adequate transmission of torque to the lead tip.
  3. 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:
  1. 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).
  2. 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.
  3. 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.
  4. 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.