Among patients who were eligible for CRT, left bundle branch area pacing (LBBAP) was not found to be noninferior to biventricular pacing (BiVP) in the intention-to-treat analysis, according to results from the LEFT-BUNDLE-CRT trial published April 14 in EHJ.

The investigator-initiated study, conducted at 11 centers across Spain, randomized 176 patients (average age, 67; 33% women) with guideline-based CRT indications and LBBB per Strauss criteria to either BiVP-CRT (n=84) or LBBAP-CRT (n=92). Baseline characteristics were similar between the two groups, except for a wider intrinsic QRS in the LBBAP than the BiVP group (median 172 ms vs. 165 ms).

There was a high level of treatment crossover, with 17 in the BiVP group and nine in the LBBAP group crossing over. Along with withdrawals, this resulted in 74 patients in the BiVP group and 87 patients in the LBBAP in the intention-to-treat analysis. For the on-treatment analysis, there were 69 patients and 92 patients in the two groups, respectively.

Total implant time was similar between the groups, but fluoroscopy time was significantly shorter in the LBBAP group (median 11 min. vs. 19 min in the BiVP group; p=0.01).

Results at six months showed that, in the intention-to-treat population, 94.6% of BiVP patients vs. 89.7% of LBBAP patients met the primary endpoint of a positive CRT response, defined as either an improved clinical composite score (77% vs. 68%, respectively) or a ≥15% reduction in left ventricular end-systolic volume (LVEDD) (85% vs. 79%); the results did not meet the noninferiority threshold (p=0.12).

In the on-treatment analysis, there was comparable efficacy between the two treatment strategies, with a positive CRT response in 92.8% of BiVP patients and 91.3% of LBBAP patients – yet the researchers caution this is an exploratory finding.

In other findings, there was a comparable and significant improvement in LVEF (+16.3 and +14.4 with BiVP and LBBAP, respectively) at six months and was sustained at 12 months. The proportion of patients who had a reduction in LVEDD ≥15% at six months was similar in the intention-to-treat analysis (84.9% vs. 79.1%; p=0.34) and on-treatment analysis (84.1% vs. 80.0%) in the two groups respectively. Comparable improvements were observed in six-minute walking distance and EQ-5D score at six and 12 months in both groups.

Rates of acute complications and adverse events were also similar across groups.

"The relatively high and asymmetric crossover rate, particularly in the BiVP group, complicates interpretation of the intention-to-treat results," write investigators Óscar Cano, MD, et al. "In this context, the on-treatment analysis provides complementary insight into the effects of the pacing strategies actually delivered and suggested similar outcomes between LBBAP-CRT and BiVP-CRT; however, given the discordance between analyses, these findings should be interpreted as exploratory."