Study limitations

This was a single center study with only 35 patients. We cannot exclude the possibility that there is a small fraction of patients whom the lead can be advanced successfully but the left bundle cannot be captured.
LBAP is a relatively new procedure, and success may be limited by operator experience. In our cohort, the procedures were all performed by a single experienced operator. The patients where lead advancement was not achieved were widely distributed in terms of procedure dates, so it was not due to problems earlier on in the learning curve. The time-order of cases where lead advancement was not achieved was 5,7,11,29 and 36.
The distribution of our patient cohort is tilted toward a greater extent of scar because it is from a tertiary center with many cases of advanced heart failure. However, this does not detract from the observation that when basal septal scar was extensive, the lead was much less likely to be advanceable but (once advanced) the left bundle could be successfully stimulated.
Our center used only one type of lead for the left bundle. We cannot exclude the possibility that a different type of lead such as a stylet driven lead may have different advance-ability characteristics. Nevertheless, there is a clear need for better custom-made tools for this task.