The following are key points to remember from a state-of-the-art review on cardiac conduction system pacing:

1. The field of cardiac conduction system pacing has changed rapidly in the last several years.
2. Since the initial description of His bundle pacing targeting the conduction system, recent advances in pacing the left bundle branch (LBBB) and its fascicles have evolved.
3. Conduction system pacing using His bundle pacing (HBP) or left bundle branch area pacing (LBBAP) has the potential to restore or preserve normal physiological activation. LBBAP includes both LBBP where there is clear evidence of direct LBB capture and left ventricular septal pacing (LVSP) without direct capture of the LBB.
4. Available evidence suggests that HBP-cardiac resynchronization therapy (CRT) has the potential to deliver more effective ventricular resynchronization and improve cardiac function in patients when LBBB can be corrected successfully with HBP-CRT.
5. LBBAP offers several potential technical advantages, compared to HBP using currently available tools, including low and stable thresholds, the potential to treat more distal conduction system disease, and potentially a faster learning curve.
6. Whereas LBBAP offers several technical advantages compared to HBP, a potential disadvantage is that it results in less physiological biventricular activation, because RV activation typically does not occur via the conduction system.
7. Both LBBP and LVSP provide more physiological ventricular activation than right ventricular (RV) pacing despite delayed RV activation and a wider QRS interval, which in V1 has a pseudo-RBBB morphology.
8. Of note, confirmation of conduction system capture and restoration of electrical synchrony is essential for successful CRT. Confirmation of His bundle capture is generally quite straightforward because output-dependent transitions in QRS morphology are observed in >90% of cases.
9. Endocardial mapping of His bundle and fascicular potentials to prove LBB capture has application mainly for mechanistic investigation but can be of practical use if dual-lead implantation technique is employed.
10. Finally, large-scale randomized clinical trials are necessary to establish the role of cardiac conduction system pacing in the management of bradycardia and heart failure.

Clinical Topics: Arrhythmias and Clinical EP, Cardiovascular Care Team, Heart Failure and Cardiomyopathies, Prevention, Implantable Devices, EP Basic Science, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias, Acute Heart Failure

Keywords: Arrhythmias, Cardiac, Bradycardia, Bundle of His, Cardiac Conduction System Disease, Cardiac Resynchronization Therapy, Heart Conduction System, Heart Failure, Heart Ventricles, Pacemaker, Artificial, Secondary Prevention

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