Preliminary results of a cross-over trial comparing CLS and VVIR pacing in LBBAP patients with chronotropic incompetence
B Wrobel, J Karpiak, M Wojcik, P Szpunar, I Wojtas, A PrzybylskiAbstract
Background
Chronotropic incompetence (CI) is frequent in patients with permanent atrial fibrillation (AF) treated with ventricular pacing and is associated with exercise intolerance and reduced quality of life. Left bundle branch area pacing (LBBAP) restores physiological ventricular activation, while closed-loop stimulation (CLS) adapts pacing rate to contractility changes, potentially providing a more physiological rate response than standard VVIR mode. However, data on CLS in LBBAP patients with CI is limited.
Purpose
To compare CLS and conventional VVIR pacing in patients with permanent AF and CI treated with LBBAP.
Methods
This prospective, single-blind, cross-over study included patients with permanent AF, CI, and >50% ventricular pacing burden after LBBAP implantation. During the first phase, patients were evaluated in CLS mode using a standardized protocol: handgrip test (5 min at 30% maximal strength), mental stress test (Paced Auditory Serial Addition Test – PASAT), and treadmill exercise test (modified Bruce protocol), all under continuous 12-lead ECG monitoring. Between tests, ≥5 min rest was allowed for heart rate recovery. Device follow-up was performed at each visit. After one month, the pacing mode was switched to VVIR, and all assessments were repeated. The quality of life was assessed using the EQ-5D-5L questionnaire, and patients were asked to indicate their preferred mode.
Results
Twenty-one patients completed both phases. Exercise duration (4.9 ± 6 vs 3.7 ± 4 min, p = 0.19), METs (3.8 ± 3 vs 2.6 ± 3, p = 0.11), ΔHR (33.9 ± 12 vs 34 ± 15 bpm, p = 0.94), and Borg scale (15 ± 2 vs 15 ± 2, p = 0.16) did not differ between CLS and VVIR. CLS induced a higher BP response during PASAT (ΔSBP 5 ± 9 vs 4 ± 5 mmHg, p = 0.03) but a lower proportion of correct answers (36.7 ± 23 vs 61.4 ± 15%, p < 0.001). Handgrip ΔHR tended to be higher with CLS (7 ± 20 vs 0 ± 5 bpm, p = 0.10). Device parameters were comparable except for higher ventricular pacing percentage (94 ± 16 vs 87 ± 40%, p = 0.03) and impedance (354 vs 340 Ω, p = 0.001) in CLS. EQ-5D-5L scores were similar: Visual Analogue Scale (VAS) 69.4 (24) vs 64.1 (27), p = 0.83; index 0.97 (0,126) vs 0.94 (0,078), p = 0.08.
Conclusion
In patients with permanent AF, CI, and LBBAP, CLS did not significantly improve exercise capacity or handgrip performance compared with VVIR pacing. CLS elicited higher BP responses but lower cognitive performance during mental stress, with no relevant differences in device parameters. Larger studies are warranted to define its clinical role.ResultsMethods Scheme