Selective LBB pacing yields the greatest acute hemodynamic benefit, and the hemodynamic-optimal atrioventricular interval is shorter than the electrical-optimal atrioventricular interval, suggesting that modest atrioventricular interval shortening after electrical optimization may better maximize hemodynamics.
Key Findings
Results
All left bundle-branch (LBB) area pacing modalities produced significantly narrower QRS duration than right ventricular septal pacing in patients with heart failure, reduced ejection fraction, and LBB block.
Twenty-four patients underwent sequential testing of RV septal, LV septal, nonselective LBB, and selective LBB pacing during CRT implantation in a prospective, within-subject physiological study.
All comparisons versus RV septal pacing had P<0.01.
Results
Selective LBB pacing produced the greatest acute hemodynamic improvement in systolic blood pressure among the modalities tested.
ΔSBP at the AV interval maximizing SBP improvement was 16.3±5.2 mm Hg for selective LBB pacing.
This exceeded LV septal pacing (13.5±6.2 mm Hg) and nonselective LBB pacing (12.8±6.3 mm Hg); all P<0.05.
Hemodynamics were assessed with beat-to-beat systolic blood pressure.
Results
At the AV interval that maximized SBP improvement, QRS duration remained narrower with LBB area pacing than with RV septal pacing.
Electrical endpoints were QRSd and vectorcardiographic QRS area.
This comparison was made at the hemodynamically optimal AV interval rather than the electrically optimal one.
Results
The AV interval that maximized ΔSBP was consistently shorter than the AV interval that minimized QRSd across all pacing modalities.
Mean difference was 18–29 ms across modalities.
The AV interval producing maximal SBP improvement was compared with that producing the narrowest QRSd within each modality.
Conclusions
The authors conclude that modest AV interval shortening after electrical optimization may better maximize hemodynamics.
QRSd-guided AV optimization may not yield the greatest hemodynamic benefit.
This is based on the observed gap between the electrical-optimal and hemodynamic-optimal AV intervals.
What This Means
This study looked at different ways of pacing the heart's left conduction system in 24 patients with heart failure, weak pumping, and a delay in the heart's left-sided electrical signal (left bundle-branch block). During implantation of a cardiac resynchronization device, the researchers tested four pacing approaches in each patient and measured electrical activation (QRS width) and blood pressure on a beat-to-beat basis.
All three approaches that paced the left bundle-branch area produced a narrower QRS than pacing the right-sided septum. Selective left bundle-branch pacing gave the largest immediate rise in systolic blood pressure (about 16 mm Hg), more than the other left-sided approaches (about 13 mm Hg each). The timing between atrial and ventricular pacing that gave the best blood pressure was consistently 18–29 ms shorter than the timing that gave the narrowest QRS.
This research suggests that selective capture of the left bundle may offer the best short-term hemodynamic effect, and that adjusting timing using QRS width alone may not give the best blood pressure response. The findings come from a small study measuring immediate effects during implantation, so they do not show long-term outcomes.
Su Y, Yu Z, Xiao Z, Pan L, Lu H, Chen J, et al.. (2026). Evaluation of Acute Electrical and Hemodynamic Improvement During Left Bundle-Branch Area Pacing Modalities for Resynchronization Therapy.. Journal of the American Heart Association. https://doi.org/10.1161/JAHA.126.049208