What is left bundle branch (LBB) pacing?

Left Bundle Branch Pacing: A Novel Physiologic Pacing Approach

Left bundle branch pacing (LBBP) is a novel physiologic pacing technique that delivers electrical stimulation directly to the left bundle branch area via a transventricular septal approach, providing more synchronized left ventricular activation compared to traditional right ventricular pacing while offering technical advantages over His bundle pacing.

Definition and Mechanism

LBBP involves:

• Placement of a pacing lead through the interventricular septum to directly capture the left bundle branch area
• Stimulation of the left bundle branch conduction system to achieve physiologic activation of the left ventricle
• Creation of a more synchronized ventricular contraction pattern than conventional right ventricular pacing

Clinical Applications

LBBP has emerged as a promising alternative in several clinical scenarios:

1. As an alternative to biventricular pacing for cardiac resynchronization therapy (CRT)

   • Particularly beneficial in patients with heart failure and left bundle branch block (LBBB)
   • Recent studies show LBBP-CRT provides greater improvement in left ventricular ejection fraction (LVEF) than biventricular pacing (BiVP-CRT) 1
   • Demonstrates superior reduction in left ventricular end-systolic volume and NT-proBNP levels 1

2. For patients with heart failure and right bundle branch block (RBBB)

   • Traditional BiVP-CRT has limited efficacy in this population
   • LBBP has shown 88% implantation success rate with significant improvements in LVEF (from 35% to 43%) 2
   • Clinical and echocardiographic response observed in approximately 60% of patients 2

3. As an alternative to His bundle pacing

   • Overcomes limitations of His bundle pacing including:
     • Challenging implantation technique
     • High pacing thresholds
     • Early battery depletion
   • Provides similar clinical benefits with more favorable technical parameters 3, 4

Advantages Over Traditional Pacing Methods

1. Compared to right ventricular pacing:

   • Prevents electric and mechanical dyssynchrony
   • Reduces risk of atrial arrhythmias and heart failure 3
   • Provides more physiologic ventricular activation

2. Compared to His bundle pacing:

   • Higher success rate in patients with wide QRS complexes
   • Lower pacing thresholds (0.49V vs 1.35V) 4
   • Higher R-wave amplitude (11.2mV vs 3.8mV) 4
   • Improved lead stability and performance 5

3. Compared to biventricular pacing:

   • More effective QRS narrowing (71% achieving QRS <120ms vs 30% with BiVP) 5
   • Greater improvement in LVEF and reduction in LV end-systolic volume 5
   • Better quality of life outcomes and reduced healthcare utilization 5

Technical Considerations

• Implantation involves advancing the lead through the right ventricular septum to reach the left bundle branch area
• Successful LBBP is characterized by:
  • Narrow paced QRS duration
  • Large R waves
  • Fast synchronized left ventricular activation
  • Correction of left bundle branch block 3
• Pacing parameters typically show excellent stability during follow-up 2

Clinical Outcomes

Recent evidence demonstrates that LBBP:

• Improves LVEF by approximately 24% at one-year follow-up 4
• Achieves normalized LVEF in approximately 70% of patients 4
• Significantly improves NYHA functional class 5
• Reduces heart failure hospitalizations and healthcare utilization 5

Current Limitations and Future Directions

• While promising, LBBP is still a relatively new technique
• Long-term data on lead performance and clinical outcomes are limited
• Further validation through randomized clinical trials is needed 3
• The technique requires specialized training and expertise

Conclusion

LBBP represents an important advancement in cardiac pacing technology that may overcome limitations of both conventional right ventricular pacing and biventricular pacing for CRT. Its ability to provide more physiologic ventricular activation with favorable technical parameters makes it a promising option for patients requiring cardiac pacing, particularly those with heart failure and conduction disorders.