3.3 Continuous lead stylet pacing to guide LBBAP
In the feasibility-group, all patients demonstrated selective (14/20 patients, 70%) or non-selective (6/20 patients, 30%) LBB capture at the end of the continuous transseptal-screwing maneuver. This was associated with a short and stable mean pLVAT of 73ms [IQR 68-80.5] and short median paced QRS duration of 120ms [IQR 112-152ms]. The screwing maneuver duration was highly variable and ranged from 7.8 seconds to 27 seconds. During lead deployment the impedance evolution was recorded for off-line analysis. However, in 5 patients the recording quality was insufficient, and those impedance data were discarded.
As the lead progressed from the RV septum to the LV sub-endocardial region, a small increase followed by progressive decrease of the unipolar pacing impedance was noted in most patients (with a mean impedance difference 143 ± 87 Ohm) ending with a discrete increase just before reaching final position (Figure 4). The impedance at final position ranged from 340 to 728 Ohm. Two patients showed an unexpected progressive increase in impedance from 590 to 715 Ohm and from 405 to 674 Ohm. This was associated with a suboptimal paced QRS morphology without qR pattern in precordial ECG lead V1 in both patients, but with narrow QRS (120ms) and pLVAT (74ms) in the first patient and with clear LBB potential on local EGM and narrow QRS and PLVAT (126ms and 71ms respectively) in the second patient. No helix retraction was observed in these 2 patients.