Dr. Parikshit S. Sharma, MD, MPH, FACC, FHRS, Section Head of Electrophysiology at Cleveland Clinic Florida (Weston), is among the world's most prolific researchers in conduction system pacing. With over 130 peer-reviewed publications, his work — particularly through the International Collaborative LBBAP Study Group (I-CLAS) — has fundamentally shaped clinical practice around Left Bundle Branch Area Pacing (LBBAP) as an alternative and often superior strategy to conventional right ventricular pacing and biventricular cardiac resynchronization therapy (CRT).
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Landmark Registry & Clinical Outcomes Studies
1
Clinical Outcomes of LBBAP Compared to Right Ventricular Pacing: Results from the Geisinger-Rush Conduction System Pacing Registry
Heart Rhythm, 2022 — Sharma PS, Patel NR, Ravi V, et al.
This registry-based observational study — with Dr. Sharma as first author — compared LBBAP versus conventional right ventricular pacing (RVP) in 703 patients undergoing pacemaker implantation for bradycardia indications. LBBAP achieved a significantly narrower QRS duration (121 ± 23 ms vs. 156 ± 27 ms with RVP) and resulted in a substantially lower primary composite outcome of death, heart failure hospitalization (HFH), or upgrade to biventricular pacing (10.0% vs. 23.3%; HR 0.46; P <0.001). In patients with pacing burden >20%, LBBAP reduced the primary outcome to 8.4% vs. 26.1% with RVP — a more than three-fold reduction in risk.
First-Author Study
RVP vs. LBBAP
Geisinger-Rush Registry
2
Left Bundle Branch Area Pacing for Cardiac Resynchronization Therapy: Results From the International LBBAP Collaborative Study Group
JACC: Clinical Electrophysiology, February 2021 — Vol. 7(2):135–147
One of the first large international multicenter studies to assess LBBAP specifically as a CRT modality. Co-authored by Dr. Sharma as part of the I-CLAS collaborative, this foundational paper enrolled patients with LVEF <50% and guideline CRT indications at multiple centers worldwide. It demonstrated high LBBAP implant success rates with favorable electrical resynchronization parameters and served as the blueprint for the entire I-CLAS research program.
I-CLAS Founding Study
CRT
Multicenter
3
Comparison of Left Bundle Branch Area Pacing and Biventricular Pacing in Candidates for Resynchronization Therapy
Journal of the American College of Cardiology, 2023 — Vol. 82(3):228–241
A landmark observational study comparing LBBAP versus biventricular pacing (BVP) in patients with LVEF ≤35% undergoing CRT for Class I or II indications at 15 international centers (January 2018 – June 2022). The primary endpoint was the composite of death or heart failure hospitalization. This paper, published in the flagship JACC journal, provided the strongest evidence to date supporting LBBAP as a viable — and potentially superior — alternative to BVP-CRT in patients with severely reduced ejection fraction.
JACC Publication
LVEF ≤35%
15 Centers
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The I-CLAS Series: International Collaborative LBBAP Studies
4
Sex-Specific Outcomes of LBBAP Versus Biventricular Pacing: Results From I-CLAS
JACC: Clinical Electrophysiology, January 2024 — Vol. 10(1):96–105
This study analyzed sex-specific outcomes in 1,778 patients (575 female, 1,203 male) from the I-CLAS cohort. Given that conventional CRT has historically shown greater benefit in women, this analysis investigated whether LBBAP-CRT preserves or enhances this sex-based advantage. The study represents an important step toward personalized conduction system pacing strategies and was co-authored by Subzposh, Sharma, Cano, Vijayaraman, and an international team of electrophysiologists.
Sex-Specific Analysis
1,778 Patients
I-CLAS
5
Conduction System Pacing vs. BVP for CRT in Patients with Heart Failure and Mildly Reduced EF (HFmrEF): Results from I-CLAS
Heart Rhythm, October 2024
Addressing a historically underrepresented population, this I-CLAS analysis focused on patients with heart failure with mildly reduced ejection fraction (HFmrEF, LVEF 36–50%) who have guideline indications for CRT. Conduction system pacing (LBBAP and His bundle pacing) was compared to BVP in this challenging subgroup, expanding the evidence base for physiological pacing to patients who fall between the HFrEF and HFpEF spectra.
HFmrEF
CSP vs. BVP
I-CLAS
6
LBBAP vs. BVP in Patients with LVEF ≤50% Undergoing CRT: Results from I-CLAS
Heart Rhythm, August 2025 — Vol. 22(8)
The most recent I-CLAS publication (at time of writing), this multicenter observational study enrolled patients with LVEF ≤50% at 18 international centers from January 2018 to June 2023. The primary endpoint was a composite of all-cause mortality or first heart failure hospitalization. With 18 centers and a 5-year enrollment window, this paper represents the largest and most current I-CLAS dataset comparing LBBAP with BVP for CRT candidacy across the full spectrum of reduced ejection fraction.
Most Recent I-CLAS
18 Centers
LVEF ≤50%
7
Rescue LBBAP in Coronary Venous Lead Failure or Non-Response to Biventricular Pacing: Results from the International LBBAP Collaborative Study Group
JACC: Clinical Electrophysiology (I-CLAS series)
An important clinical application paper examining LBBAP as a "rescue" strategy in patients who experienced coronary venous lead failure or failed to respond to conventional BVP-CRT. This work demonstrates LBBAP's utility as a second-line or alternative approach when traditional CRT fails, broadening the clinical pathway for patients with refractory heart failure seeking resynchronization.
Rescue CRT
CRT Non-Responders
I-CLAS
8
Left Bundle Branch-Optimized Cardiac Resynchronization Therapy (LOT-CRT): Results from an International LBBAP Collaborative Study Group
JACC: Clinical Electrophysiology (I-CLAS series)
LOT-CRT is a hybrid approach combining LBBAP with a coronary sinus lead to achieve optimized biventricular resynchronization in patients where standalone LBBAP may be insufficient. This study evaluated outcomes of this novel combined strategy from the I-CLAS international registry, representing an evolution in thinking beyond pure conduction system pacing toward tailored resynchronization strategies.
LOT-CRT
Hybrid CRT
Innovation
Technical, Procedural & Diagnostic Papers
9
His-Purkinje Conduction System Pacing Following TAVR: Feasibility and Safety
JACC: Clinical Electrophysiology, June 2020 — Vol. 6(6):649–657
This multicenter study evaluated His-Purkinje conduction system pacing in patients requiring permanent pacing after transcatheter aortic valve replacement (TAVR). In a challenging post-TAVR anatomy, LBBAP achieved success in 93% of attempts versus 63% for His bundle pacing (HBP), and was associated with lower pacing thresholds and higher R-wave amplitudes. The study established LBBAP as the preferred conduction system pacing approach in post-TAVR patients — a clinically critical population with growing implantation numbers worldwide.
Post-TAVR Pacing
HBP vs. LBBAP
Feasibility
10
Evaluation of the Criteria to Distinguish Left Bundle Branch Pacing from Left Ventricular Septal Pacing
Co-authored with Vijayaraman, Wu, Huang, et al.
A technically oriented paper addressing one of the most nuanced diagnostic challenges in the LBBAP field: distinguishing true left bundle branch pacing (LBBP) from LV septal pacing (LVsP). Since these two subtypes of LBBAP differ in terms of His-Purkinje recruitment and potential long-term outcomes, establishing reliable electrocardiographic and intracardiac criteria is essential for procedural standardization and outcome comparison across studies.
Diagnostic Criteria
LBBP vs. LVsP
Technical
11
Complications, Troubleshooting, and Follow-Up for Left Bundle Branch Area Pacing
Arrhythmia & Electrophysiology Review, 2025 — Vol. 14:e20
A comprehensive open-access clinical review of unique LBBAP complications including septal perforation, exit block, phrenic nerve stimulation, and lead dislodgement. The paper provides practical guidance on device programming, remote monitoring follow-up, and procedural troubleshooting. Given the unique anatomical territory of LBBAP compared to RV pacing or HBP, this review serves as an essential clinical resource for electrophysiologists adopting or expanding conduction system pacing programs.
Open Access
Complications
Clinical Review
Device Programming
Frontier Research (2025)
12
Optimizing Conduction System Pacing: Is Hierarchical Physiological Pacing the Answer?
Heart Rhythm, April 2025
Dr. Sharma's most recent publication at the time of this writing explores the concept of "hierarchical physiologic pacing" — a tiered decision framework for selecting the optimal conduction system pacing modality (HBP vs. LBBAP vs. LV septal pacing) based on patient-specific anatomy, electrophysiology, and hemodynamic goals. This represents the current philosophical frontier of his research: moving beyond simple RVP vs. LBBAP comparisons toward a nuanced, patient-tailored pacing strategy.
2025 Frontier
Hierarchical CSP
Physiological Pacing
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Frequently Asked Questions
What is Left Bundle Branch Area Pacing (LBBAP)?
Left Bundle Branch Area Pacing (LBBAP) is a conduction system pacing technique that directly engages the His-Purkinje system through deep septal screw-in lead deployment at the level of the left bundle branch. Unlike conventional right ventricular pacing — which causes abnormal ventricular activation and carries risk of pacing-induced cardiomyopathy — LBBAP achieves near-physiological ventricular activation, narrower QRS duration, and preserved left ventricular function. It encompasses both true left bundle branch pacing (LBBP) and left ventricular septal pacing (LVsP).
What is the I-CLAS study and why does it matter?
The International Collaborative LBBAP Study (I-CLAS) is an ongoing multicenter, multinational research consortium co-led by Dr. Parikshit Sharma and Dr. Pugazhendhi Vijayaraman. It has enrolled thousands of patients across 15–18 international centers and produced a series of landmark comparative studies between LBBAP and biventricular pacing (BVP) for CRT. I-CLAS data have shown consistent advantages for LBBAP across multiple EF subgroups (≤35%, ≤50%, HFmrEF), sexes, and clinical contexts (de novo CRT, rescue CRT), making it the most comprehensive real-world evidence base for conduction system pacing.
How does LBBAP compare to biventricular pacing for CRT?
Multiple I-CLAS publications by Dr. Sharma and colleagues demonstrate that LBBAP achieves equivalent or superior clinical outcomes to biventricular pacing (BVP) for CRT. Key findings include: significantly narrower QRS duration (near-normal physiological activation), significant reductions in the composite endpoint of death or heart failure hospitalization across multiple EF subgroups, comparable or superior outcomes in both male and female patients, higher procedural success rates vs. His bundle pacing in challenging anatomies (post-TAVR), and utility as a rescue strategy when BVP fails.
Who is Dr. Parikshit Sharma at Cleveland Clinic Florida?
Dr. Parikshit S. Sharma, MD, MPH, FACC, FHRS is the Section Head of Electrophysiology at Cleveland Clinic Florida (Weston). Previously Section Chief at Rush University Medical Center in Chicago, he is a world-recognized pioneer in conduction system pacing with over 130 peer-reviewed publications. He received the prestigious Joan and Douglas P. Zipes Publication of the Year Award in 2019 from the Heart Rhythm Society. He currently leads Cleveland Clinic Florida's EP program, overseeing services from Broward to Indian River County, and is establishing an EP fellowship program opening in July 2026.
What are the unique complications of LBBAP compared to conventional pacing?
LBBAP involves deep septal lead deployment, which carries unique complication risks not seen with conventional RV pacing. These include interventricular septal perforation, inadvertent left ventricular deployment, exit block (due to fibrotic encapsulation in the deep septum), phrenic nerve stimulation (from lateral septal placement), and challenges in lead extraction given the degree of septal fibrous tissue ingrowth. Complication rates are generally low but require meticulous follow-up with attention to pacing threshold trends, impedance, and sensing parameters — topics covered extensively in Dr. Sharma's 2025 Arrhythmia & Electrophysiology Review paper.
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