Comparative Left Bundle Branch Block Correction With Physiological Pacing-An Intrapatient Electrocardiographic Study

Several studies have compared His bundle pacing (HBP) and left bundle branch area pacing (LBBAP) regarding paced QRS duration and clinical outcomes. This study compared acute intraprocedural depolarization and repolarization electrocardiographic changes between corrective HBP and LBBAP in the same patient with baseline left bundle branch block and reduced left ventricular ejection fraction.

Thirty-six patients with successful corrective LBBAP for cardiac resynchronization therapy (CRT), in whom corrective HBP was also demonstrated, were retrospectively reviewed. QRS duration (QRSd), QRS and T wave axes, left ventricular activation time (LVAT), corrected QT (QTc) and JT (JTc) intervals, QT dispersion (QTd), corrected T wave peak-to-end interval (Tpec) and Tpec/QTc were measured for both instances.

Both pacing techniques produced significantly narrower QRS complexes than the baseline values without differences between them. The LVAT was shorter with HBP than baseline without reaching statistical significance. On the other hand, LBBAP was associated with significantly shorter LVATs than both baseline and HBP values. HBP and LBBAP had a similar impact on repolarization parameters, significantly reducing the QTc, JTc and Tpec. Final left bundle branch pacing was achieved in 24 and final left ventricular septal pacing in 12 patients. The former resulted in a shorter QRS duration and a significantly faster LVAT. Also, capturing the left conduction system reduced the QTc and JTc intervals, albeit without statistical significance.

In patients with LBBB and an indication for resynchronization therapy, HBP and LBBAP resulted in similar significant improvements in electrocardiographic depolarization and repolarization parameters.