Determinants of mid-term response to left bundle branch pacing in heart failure patients with left bundle branch block.

BACKGROUND

Response to left bundle branch pacing (LBBP) varies in patients with left bundle branch block (LBBB). We aimed to investigate whether clinical response to LBBP was associated with ventricular electricity, volume, and myocardial glucose uptake in nonischemic cardiomyopathy (NICM) patients with LBBB.

METHODS

Consecutive NICM patients who received LBBP with successful LBBB correction were prospectively enrolled. Electrocardiographic QRS duration (QRSd) and left ventricular volume were measured. Myocardial glucose uptake was accessed by means of 18F-fluorodeoxyglucose (FDG) positron emission tomography. The standardised uptake value (SUV) and target-to-background ratio (TBR) of 18F-FDG uptake were analysed.

RESULTS

After 6 months of LBBP, 24 patients responded to LBBP (left ventricular end-systolic volume reduction (ΔLVESV%) 31.7 ± 18.7%) and 12 did not (ΔLVESV% 1.9 ± 1.3%) although similar QRSd reductions with LBBP were observed (55.57 ± 16.93 ms in the response group vs 57.40 ± 17.69 ms in the nonresponse group; P = 0.780). The univariate logistic regression model identified risk factors (baseline QRSd, R-wave peak time, left ventricular end-diastolic volume (LVEDV), LVESV, TBRmean-septum, and SUVmax-septum; P < 0.05) for nonresponders, only LVEDV (odds ratio [OR] 1.32, 95% confidence interval [CI] 1.18-1.48; P = 0.025) and TBRmean-septum (OR 0.85, 95% CI 0.783-0.931; P = 0.005) were predictors of nonresponders in the multivariate logistic regression model.

CONCLUSIONS

LBBP significantly shortened QRSd in NICM patients with LBBB, although 6-month clinical response to LBBP varied, with 33% nonresponders. Larger LVEDV and more depressed glucose uptake were associated with higher odds of LBBP nonresponse than the electrical variables of QRSd and ΔQRSd. Besides ventricular electrical desynchrony, volume and myocardial metabolism should be considered for choice of pacing therapy.

TRIAL REGISTRATION: ChiCTR2300070954.