Septal scar predicts failure of lead advancement to the left bundle area

Background Left bundle area pacing is growing in use both for bradycardia pacing and cardiac resynchronization, but implants are not always successful. We prospectively studied consecutive patients to determine whether septal scar contributes to implant failure. Methods Patients scheduled for left bundle area pacing, using the 3830 Selectsecure lead were prospectively enrolled. All patients underwent standardized scar assessment by cardiac MRI with late gadolinium enhancement imaging. Scar burden was quantified as the proportion of basal septal segments showing late enhancement. Results 35 patients were recruited: 29 male, mean age 68 years, 10 with ischemic and 16 with dilated cardiomyopathy. Pacing indication was bradycardia in 26% and cardiac resynchronization in 74%. In 5/35 (14%) it was not possible to advance the lead through the ventricular septum. Basal septal late gadolinium enhancement was significantly more extensive in these patients (median 67%, IQR 58-69.5) compared to the other 30 (median 10%, IQR 0-20, p = 0.0006). There was no significant correlation between the paced QRS duration achieved and the extent of basal septal scar (r = 0.06, P = 0.75). Conclusions Failure to deliver a lead to the left bundle area is strongly associated with a (very) high burden of scar in the basal septum. Once the lead is delivered, however, the electrical response is independent of scar burden. This suggests that it would be worth developing delivery tools to tackle scarred basal septa, because if the lead could be delivered the electrical capture might still achieve a narrow QRS.