LBB performs better than standard BiV pacing for CRT in chronic heart failure

For chronic heart failure (HF) patients requiring cardiac resynchronization therapy (CRT), the use of left bundle branch (LBB) pacing yields superior clinical outcomes compared with the traditional biventricular (BiV) pacing, as shown in the results of the HeartSync-LBBP trial.

Over a median follow-up of 36 months, the primary endpoint of composite all-cause mortality and HF hospitalization events occurred with significantly less frequency among patients who received LBB pacing-guided CRT than among those who received BiV pacing-guided CRT (8 percent vs 32 percent; hazard ratio [HR], 0.26, 95 percent confidence interval [CI], 0.12–0.57; p<0.01), reported lead investigator Dr Xueying Chen from Zhongshan Hospital, Fudan University in Shanghai, China. [Chen X, et al, EHRA 2025]

The result was consistent across subgroups defined by age, sex, nonischaemic cardiomyopathy status, hypertension, diabetes, baseline QRS duration, NYHA class, and left ventricular ejection fraction, Chen added.

Secondary outcomes

When the composite endpoint was analysed separately, LBB pacing was associated with significantly fewer HF hospitalizations compared with BiV pacing (HR, 0.23, 95 percent CI, 0.10–0.52; p<0.01), with no difference in all-cause mortality (HR, 0.40, 95 percent CI, 0.08–2.04; p=0.25).

QRS duration decreased in both treatment groups, but the narrowing was significantly greater with LBB pacing (from 169.8 to 120.6 ms) than with BiV pacing (from 167.0 to 137.4; p<0.01 for between-group comparison), Chen noted.

Additionally, echocardiographic data indicated that compared with the BiV group, the LBB group had a substantially greater mean LVEF at 36 months (47.3 percent vs 41.5 percent; p<0.01), as well as lower LV end-systolic diameter (41.8 vs 48.1 mm; p<0.01) and LV end-diastolic diameter (55.3 vs 60.3 mm; p<0.01).

In terms of response, significantly more patients in the LBB group achieved super response based on an LVEF increase of at least 15 percent or LVEF reaching 50 percent or greater (65 percent vs 44 percent; p<0.01). There was no significant between-group difference in the percentage of patients achieving response defined as an LVEF improvement of at least 5 percent (90 percent vs 84 percent; p=0.21).

HeartSync-LBBP population

HeartSync-LBBP included 200 patients (mean age about 65 years, 68 percent male) enrolled at six centres in China. These patients had chronic systolic HF, left bundle branch block, LVEF of not more than 35 percent, and NYHA class II-IV symptoms despite having taken guideline-directed medical therapy for at least 3 months.

At baseline, the mean LVEF was 28 percent, with most patients (83 percent) having nonischemic cardiomyopathy. Roughly 90 percent of patients were on guideline-directed medical therapy comprising an angiotensin-converting-enzyme inhibitor/angiotensin receptor blocker/angiotensin receptor-neprilysin inhibitor, a beta-blocker, and spironolactone.

Of the patients, 100 were allocated to the LBB group and 100 to the BiV group. Some patients crossed over between treatment groups, with LBB pacing used in six patients in the BiV group due to unfavourable venous anatomy (n=4), high pacing threshold (n=1), or phrenic nerve stimulation (n=1). BiV pacing was used in two patients in the LBB group due to a failure to screw in the lead.

Chen acknowledged that the generalizability of the results may be limited by the high percentage of men and those with nonischaemic cardiomyopathy included in the population, as well as the exclusive enrolment of Chinese patients. Moreover, the study was performed in centres with high success rates and low crossover rates, which might differ from other studies with different implant experience, she added. The lack of MRI data prior to the CRT implantation also made it difficult for the investigators to analyse the scar and aetiology of the study population.

More data needed

Study discussant Prof Jens Cosedis Nielsen from the Aarhus University Hospital in Aarhus, Denmark, congratulated Chen and colleagues for completing the HeartSync-LBBP trial as the largest investigation into the topic, with a “quite amazing difference” in the primary endpoint.

However, Nielsen pointed out that the population comprised patients at very low risk of death, with an estimated mortality rate of 1 percent per year. “At least in our institution this is a little higher, so I would question how severe this heart failure was.”

There were also potential issues surrounding blinding, HF hospitalization definition and adjudication by an endpoint committee, and steps taken to address the potential for bias when evaluating responder status, he noted. “The risk of bias may be considerable in this unblinded trial with respect to both the primary and secondary endpoints.”

Therefore, while LBB pacing was found superior to BiV pacing in this trial, more data are needed before LBB pacing-guided CRT can be broadly adopted for HF with left bundle branch block in clinical settings, according to Nielsen.