Introduction:
Despite advances in the implant technique over the last a few decades, optimal cardiac synchronization and positive response can still not be achieved in about 30% of the patients.1 More recently, conduction system pacing especially left bundle area (LBA) pacing has rapidly emerged as a potential new alternative to traditional bi-ventricular pacing through the coronary sinus (CS) and has been used in certain cases to improve the CRT response in patients who failed conventional CRT (figure 1). 2-4 Nevertheless, even with LBA pacing, there are still significant number of cases where underlying LBBB cannot be corrected. 2-4
We here report a case where a conventional CRT non-responder underwent an apparently “failed” LBA pacing implant as evidenced by the inability to correct the underlying LBBB or significantly shorten the QRS duration. However, simultaneous pacing from the previously implanted coronary sinus lead and the apparently “failed” left bundle pacing lead substantially narrowed the QRS and eventually led to CRT super response.