The Future of Cardiac Resynchronization: Emerging Studies Support Conduction-System Pacing as a Potential Alternative to Biventricular Pacing

Over the past decade, conduction system pacing (CSP) has been an emerging and more commonly used technique in the field of cardiac pacing. Conduction system pacing involves implantation of a permanent pacing lead along the cardiac conduction system and is done either through His-bundle pacing (HBP) or left bundle branch area pacing (LBBAP). Unlike traditional biventricular pacing (BVP), CSP allows for a more physiological way to pace the heart, with observational studies showing equal or even better improvements in QRS duration and LV function, and possibly greater hemodynamic benefits¹. Despite these potential benefits, randomized clinical trials comparing hard clinical outcomes for CSP versus biventricular pacing are still lacking.

Two studies^1,2, by Dr. Vijayaraman and his colleagues, recently published in Heart Rhythm, further assessed the impact of CSP on clinical outcomes and add to the growing evidence supporting CSP as a possible alternative to biventricular pacing for cardiac resynchronization therapy (CRT).

he first study reviewed retrospective data from two US centers including 477 adult patients (32% women) with an LV ejection fraction of < 35% and who had an indication for cardiac resynchronization therapy, of which 258 underwent successful CSP and 219 underwent biventricular pacing. In a mean follow-up period of 27 +12 months, the primary outcome of all-cause death or heart failure hospitalization was significantly lower with CSP versus BVP (28.3% vs 38.3%, HR 1.52; 95% CI 1.08-2.09; P = 0.013). This was primarily driven by significantly lower heart failure hospitalizations (15% vs 34%, HR 3.15, 95% CI 2.07-4.79, P <0.001) in the CSP group.

The second study presented observational data from 16 international centers to assess the feasibility and outcomes of rescue LBBAP in patients who failed BVP (due to coronary venous lead complications or failure) or were BVP non-responders (defined as LVEF improvement <5% and either worsening or unchanged functional status for at least 6 months after BVP). Rescue LBBAP was successful in 200 patients (94%) and was associated with significant clinical and echocardiographic response such as improvement in QRS duration, LV function, and NYHA functional class.

“Conduction system pacing is exciting because it permits the use of the patient’s native His-Purkinje system for ventricular activation and these data lend further support to the concept that doing so yields improvements in clinical outcomes that heart failure patients with reduced ejection fraction care about,” said Dr. George D. Veenhuyzen, Cardiac Electrophysiologist at the Libin Cardiovascular Institute, University of Calgary. Most importantly, he adds, “However, we must remain skeptical until these pacing techniques pass the test of randomized trials.”

References:

1. Vijayaraman P, Zalavadia D, Haseeb A, Dye C, Madan N, Skeete JR, Vipparthy SC, Young W, Ravi V, Rajakumar C, Pokharel P, Larsen T, Huang HD, Storm RH, Oren JW, Batul SA, Trohman RG, Subzposh FA, Sharma PS. Clinical outcomes of conduction system pacing compared to biventricular pacing in patients requiring cardiac resynchronization therapy. Heart Rhythm. 2022 Aug;19(8):1263-1271. doi: 10.1016/j.hrthm.2022.04.023. Epub 2022 Apr 29. PMID: 35500791.
2. Vijayaraman P, Herweg B, Verma A, Sharma PS, Batul SA, Ponnusamy SS, Schaller RD, Cano O, Molina-Lerma M, Curila K, Huybrechts W, Wilson DR, Rademakers LM, Sreekumar P, Upadhyay G, Vernooy K, Subzposh FA, Huang W, Jastrzebski M, Ellenbogen KA. Rescue left bundle branch area pacing in coronary venous lead failure or nonresponse to biventricular pacing: Results from International LBBAP Collaborative Study Group. Heart Rhythm. 2022 Aug;19(8):1272-1280. doi: 10.1016/j.hrthm.2022.04.024. Epub 2022 Apr 30. PMID: 35504539.