The huge popularity of conduction system pacing (CSP) , especially the Left bundle branch Area Pacing (LBBAP) has been hailed as a paradigm shift in cardiac pacing. By utilising the native His-Purkinje network, CSP promises a physiological alternative to the dys-synchronous RV pacing. However, beneath this procedural enthusiasm lies a critical, clinical assumption .It is the disregard of distal LBB integrity. In our haste to bypass proximal blocks, the electrophysiology community has mastered the art of ignoring distal conduction system disease a practice that relies more on hope than long-term, evidence-based science.
The physiological basis of LBBAP is based on capturing the main left bundle branch trunk or its proximal fascicles to downstream distal healthy Purkinje network1. In patients presenting with complete heart block , this approach looks fine , if the underlying pathology is strictly nodal or intra-Hisian. However, in progressive, degenerative conduction system disorders such as Lev’s or Lenègre’s disease fibrosis is rarely localized. It is a multi-level, diffuse process that tracks distally into the fascicles and terminal Purkinje ramifications2.
How, can we casually overlook the small but surely dangerous risk of progressive distal LBB disease in complete heart block, which can lead to unpredictable catastrophic events ? This electrical oversight finds a striking, parallel in historical pacing concepts. In patients with sinus node dysfunction (SND), the electrophysiology community long ago established that a standalone atrial lead (AAI pacing) is a clinical hazard3. The minor yet real risk of AV nodal disease progression (approximating 0.6% to 4.5% per year) almost universally mandates the placement of a backup ventricular lead, safely transitioning the strategy to dual-chamber (DDD) pacing4.
The current electrophysiology consensus downplays this distal disease , by invoking the physics of the virtual electrode. The argument is even if the localized nerve fibers directly contacting the lead tip degenerate over the subsequent decade, the high-programmed voltage outputs will maintain permanent myocardial capture, ensuring patient safety from asystole5. While this assumption satisfies the basic requirements of bradycardia support, it ignores a core fact.
Aprar from thew physiological uncertainty , there is also a significant risk of procedural failure. Real-world registries reveal that approximately 5% to 15% of patients undergo acute on-table crossovers due to septal calcification, anatomical variations, or an immediate functional failure to engage a viable conduction pathway7.
Conduction system pacing is undoubtedly a great addition to our EP armamentarium, but it must be practiced with humility in the face of unproven long-term putcome and procedural complexities. A clinical pragmatism is warranted. Conventional dual chamber (DDD) is backed by more than four decades of randomized clinical evidence.9. Until we clarify the natural history of the chronically paced, diseased left bundle, DDD pacing should remain the standard of care.
References
- Huang W, Su L, Wu S, et al. A novel pacing strategy with low and stable threshold-left bundle branch pacing. Europace. 2019;21(3):471-477.
- Lev M. Anatomic, pathologic, and electrocardiographic correlations in the atrioventricular and distal conduction system. Prog Cardiovasc Dis. 1964;7(4):317-340.
Andersen HR, Nielsen JC, Thomsen PE, et al. Long-term follow-up of patients paced in atrioventricular synchronous vs. single-chamber atrial mode for sick sinus syndrome. Lancet. 1997;350(9086):1210-1216. - Brandt J, Anderson H, Fåhraeus T, et al. Natural history of AV conduction in patients with sick sinus syndrome as related to bilateral bundle branch block. Pacing Clin Electrophysiol. 1992;15(11 Pt 2):1914-1918.
- Vijayaraman P, Sharma PS, Cano Ó, et al. Comparison of Left Bundle Branch Area Pacing and His Bundle Pacing in Bradycardia Indications. JACC Clin Electrophysiol. 2021;7(11):1433-1442.
- Jastrzębski M, Kiełbasa G, Cano Ó, et al. Left bundle branch area pacing outcomes: the MELOS registry. Eur Heart J. 2022;43(40):4161-4173.
- Heckman LI, Luermans JG, Vos LM, et al. Left Bundle Branch Area Pacing: A Comprehensive Review of Technical Aspects, Clinical Outcomes, and Future Directions. J Clin Med. 2023;12(11):3611.
- Wijesuriya N, Niederer S, de Verteuil R, et al. Extraction of conduction system pacing leads: a systematic review and international survey. Europace. 2024;26(2):euae032.
- Wilkoff BL, Cook JR, Epstein AE, et al. Dual-chamber pacing or ventricular pacing in patients with an implantable defibrillator: the DAVID trial. JAMA. 2002;288(24):3115-3123.
- Khurshid S, Epstein AE, Verdino RJ, et al. Incidence and predictors of pacing-induced cardiomyopathy. Heart Rhythm. 2014;11(9):1618-1625.
Postamble
This opinion letter is being sent to EURO PACE journal : Expecting a fast tracked rejection letter within a week or two .(Based on my past experience) They view these type of articles as destructive criticism I was told by one editor. Some one please clarify me, the difference between a constructive and a destructive critic, please)
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Dr.S.Venkatesan MD 