By Michael H. Crawford, MD, Editor
SYNOPSIS: Researchers compared biventricular pacing to left bundle branch area pacing (LBBAP) for cardiac resynchronization among patients living with heart failure caused by reduced left ventricular ejection fraction, along with either LBB block or need for ventricular pacing. The combined endpoint of all-cause mortality rates or heart failure hospitalizations was significantly lower with LBBAP.
SOURCE: Vijayaraman P, Sharma PS, Cano O, et al. Comparison of left bundle branch area pacing and biventricular pacing in candidates for resynchronization therapy. J Am Coll Cardiol 2023;82:228-241.
For patients living with heart failure (HF) caused by reduced left ventricular ejection fraction (LVEF) and either left bundle branch block (LBBB) or anticipated frequent right ventricular pacing, cardiac resynchronization therapy (CRT) by biventricular pacing (BVP) has been shown to reduce heart failure hospitalization and all-cause mortality compared to guideline-directed medical therapy (GDMT) alone.CRT system implantation is technically challenging, and some patients do not derive any benefit; some even deteriorate. Is LBB area pacing (LBBAP) effective in preserving ventricular synchrony? Vijayaraman et al assessed the clinical outcome of LBBAP compared to conventional BVP. This was a multicentered, international, observational, case-controlled study conducted at 15 centers from 2018 to 2022. Included patients recorded an LVEF of 35% or less and were undergoing BVP of LBBAP for the first time for guideline class I or II reasons. Patients were excluded if they presented with a pre-existing CRT device, CRT was unsuccessful, or they did not complete a six-month follow-up.
The choice between the two techniques was based on operator and institutional preferences. The LBB lead was inserted into the muscular interventricular septum and repositioned, if necessary, to achieve LBBAP. A right ventricular (RV) lead was placed for resynchronization. BVP was achieved in the conventional manner using an RV lead and a quadripolar LV lead whenever possible.
Patients were followed in device clinics or by remote monitoring. The BVP devices were programmed to optimize for the narrowest-paced QRS duration. The LBBAP devices were programmed to maximize the LV-RV offset, or programmed to LV-only pacing. The primary outcome was the combination of time to all-cause death or the first episode of HF. Secondary outcomes included echocardiography-determined changes in LVEF.
A total of 1,778 patients underwent successful CRT device implantation (mean age, 69 years; 32% were women). Mean LVEF was 27%, and mean QRS duration before CRT was 160 ms. LBBAP was used in 797 patients and BVP in 981 patients. The mean follow-up was 33 months (maximum = five years). LBBAP slowed paced QRS duration from a baseline mean of 161 ms to 128 ms (P < 0.001) and was significantly shorter than that achieved by BVP (144 ms; P < 0.001). A multivariate regression analysis showed the primary combined outcome percentage was significantly lower via LBBAP compared to BVP (21% vs 28%; HR, 1.50; 95% CI, 1.21-1.84; P < 0.001). Also, LVEF increased from a mean of 27% to 41% via LBBAP compared to 37% via BVP (P < 0.001). The authors concluded clinical outcome percentages for patients showing indications for CRT were higher via LBBAP than via BVP.
COMMENTARY
Patients who require ventricular pacing with a single RV lead can develop a cardiomyopathy (or worsen an existing one). BVP might not be right for some patients because of anatomic constraints, phrenic nerve stimulation, or incomplete resynchronization. This is why Vijayaraman et al explored conduction system pacing, which would mimic normal physiologic pacing of the LV. His bundle pacing, which although successful when accomplished, is a technically challenging procedure, and lead stabilization is problematic. LBBAP, in which the lead tunnels from the right side of the septum so its tip is near or in the LB, is worthy of study.
The LBBAP and BVT groups were similar in clinical characteristics but not perfectly matched; 61% showed LBB block. The GMDT rate was high (89% of patients were taking beta-blockers and 80% were taking neprilysin or an angiotensin-converting enzyme inhibitor/angiotensin receptor blocker). Procedure duration was longer for LBBAP, but fluoroscopy time was the same. Procedural complication rates were lower for LBBAP patients. The combined primary endpoint of all-cause mortality or HF hospitalization over a five-year maximum follow-up was significantly better on LBBAP, but was driven by HF hospitalization. This was significant individually, whereas mortality was not. Echocardiographic data were available for 80% of patients. These data showed LVEF increased more on LBBAP than BVP, but the absolute differences were similar (13% vs. 10%, respectively).
There were limitations to the Vijayaraman et al paper, the most important of which is the fact this was a retrospective, observational study, not a randomized, controlled trial. There may be biases and unmeasured confounders. Also, this was an on-treatment trial, so the true success of each procedure is unknown.
In addition, the echo data were not blinded or read by a core lab. Finally, two-thirds of the patients had non-ischemic cardiomyopathy or complete LBB block, which would enhance the chances of success with LBBAP. At this point, LBBAP seems to be as good or better than BVP (and perhaps easier to accomplish).
Researchers compared biventricular pacing to left bundle branch area pacing (LBBAP) for cardiac resynchronization among patients living with heart failure caused by reduced left ventricular ejection fraction, along with either LBB block or need for ventricular pacing. The combined endpoint of all-cause mortality rates or heart failure hospitalizations was significantly lower with LBBAP.
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