Conduction System Pacing Noninferior to Biventricular Pacing for HF With Wide QRS

Daniel M. Keller, PhD

April 06, 2022

Conduction system pacing (CSP) produced the same degree of cardiac resynchronization, ventricular reverse modeling, and similar clinical outcomes as did biventricular pacing (BiVP) in patients with heart failure and wide QRS, a small, randomized study has shown.

The rates of complications requiring reintervention were equivalent. However, x-ray time was slightly longer with CSP, Margarida Pujol-López, MD, Hospital Clinic de Barcelona, Spain, reported at the European Heart Rhythm Association (EHRA) 2022 congress held in Copenhagen and online.

Although CSP has emerged as an alternative to BiVP, randomized studies comparing the two are limited and have not included left bundle-branch pacing, she said. To address this question, Pujol-López and colleagues performed the Left Ventricular Activation Time Shortening with Conduction System Pacing vs Biventricular Resynchronization (LEVEL-AT) trial.

Seventy patients at a single center with an indication for cardiac resynchronization therapy were randomly assigned in this parallel group, noninferiority trial 1:1 to one or the other pacing modality (n = 35 each). For the primary endpoint of left ventricular activation time (LVAT) shortening, a noninferiority margin of -12 ms was used, measured by electrocardiographic imaging at day 45. Secondary endpoints were measured at 6 months.

Symptomatic patients with heart failure were included in the study if they were receiving optimal medical treatment, had a left ventricular ejection fraction (LVEF) ≤ 35%, left bundle-branch block (LBBB) with QRS ≥ 130 msec or a wide QRS complex ≥ 150 msec in nonleft branch block, and atrioventricular (AV) block and cardiac dysfunction. Patients were excluded if they had myocardial infarction, unstable angina, cardiac revascularization, or valve surgery/intervention within the previous 3 months, or pregnancy.

Despite the relatively small sample sizes, the CSP and BiVP groups were fairly equivalent in terms of gender (34.3%, 28.6% female, respectively), age (65.7 vs 68.1 years), ischemia (31.4% each), QRS width (177 msec, 178 msec), LBBB (65.7% each), AV block (31.4%, 25.7%), New York Heart Association (NYHA) functional class (I or II: 60%, 57.1%; III: 31.4%, 37.1%; IV: 8.6%, 5.7%), LVEF (27%, 28%), and left ventricular end-systolic volume (148 mL, 125 mL).

Patients were crossed over to the alternative procedure if the primary procedure that they had been assigned to failed. Two (6%) BiVP patients crossed over to CSP, and 8 (23%) CSP patients crossed over to BiVP.

In the CSP arm, 4 of 35 patients underwent His bundle pacing, but the majority (31/35) received left bundle-branch pacing as a first option or if His bundle pacing failed.

There were two dropouts/exclusions in each of the CSP and the BiVP arms. Thirty-three patients in each arm were included in the primary endpoint analysis at 45 days follow-up, and all 35 were included in the secondary endpoint analysis at 6 months.

CSP Noninferior to BiVP  

Results showed that CSP achieved noninferiority compared with BiVP in terms of LVAT. "That is to say that conduction system pacing achieved the same degree of cardiac resynchronization as compared to the ventricular pacing," Pujol-López said.

The LVAT difference in the CSP arm between baseline and final measurement was -28 ± 26 msec vs -21 ± 20 msec for the BiVP arm (P < .001 for noninferiority of CSP).

On the secondary endpoint of left ventricular reverse remodeling, CSP was also noninferior to BiVP: -37 ± 59 mL for CSP vs -30 ± 41 mL for BiVP (P = .04 for noninferiority).

Outcomes also showed noninferiority of CSP for heart failure hospitalization or mortality (2.9% in the CSP arm vs 11.4% for BiVP; P = .002) and for change in NYHA class at 6 months (-0.8 ± 0.8 for CSP vs 0.4 ± 0.8; P < .001).

Finally, QRS shortening showed noninferiority for CSP vs BiVP: -53 ± 20 msec vs -48 ± 20 msec, respectively; P < .001).

There were only two intraprocedure differences between CSP and BiVP, an x-ray time of 28.4 ± 12 min for CSP vs 22 ± 9 min for BiVP (P = .008); and pulse width of 0.6 ± 0.3 msec vs 0.5 ± 0.2 msec, respectively (P = .03).

There were no significant differences in total procedure time or thresholds. Complications requiring reintervention were 11.4% in each arm.

Based on such positive results, Pujol-López concluded that the "conduction system pacing technique will be a feasible alternative to the ventricular pacing."

Study discussant Christophe Leclercq, MD, PhD, University Hospital of Rennes, Hospital Pontchaillou, France, gave an analysis of the LEVEL-AT study, noting that the inclusion criteria were very broad for such a small population. Patients had LVEF below 35% with left bundle-branch block and QRS greater than 130 msec, but also allowed were patients with nonleft bundle-branch block and QRS greater than 150 msec.

He said that he noticed that the majority of patients in the CSP group received mainly left bundle-branch area pacing because only 11% of them received His pacing.

The crossover rate from BiV pacing to CSP was low (6%), "which is consistent with published studies," he noted. "But by contrast, the crossover from CSP conduction system pacing to BiV pacing was very high, 23%, which is not consistent with the data from the literature, which report success rates of 80 to 95%," he said.

Although the primary endpoint supported the noninferiority of CSP as compared with BiV pacing, when Leclercq looked more closely at the individual data in the CSP group, he said, "I noticed that there were 4 patients who have an increase in LVAT as compared to only one in the BiV group, and it was presented as an intention to treat, so I would be very happy to know for these 4 patients how they were really paced, if it was a BiV or CSP."

He said that the primary endpoint supported the noninferiority of CSP to BiV pacing in patients with heart failure and wide QRS, as assessed by LVAT. However, "I think that for the secondary endpoint of ventricular remodeling, there was a trend," he added, but suggested that the study was not powered for the other clinical endpoints.

Leclercq advised that the tools to deliver CSP need to be improved, and that a large, randomized trial comparing BiV pacing with CSP in terms of efficacy, safety, and long-term follow-up needs to be conducted before reaching any solid conclusions about CSP.

European Heart Rhythm Association (EHRA) 2022: Presented April 3, 2022.

Pujol-López has received speaker honoraria from Medtronic. Leclercq consults for Medtronic, Abbott, Biotronik, MicroPort, and Boston Scientific.

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