右脚ブロックを伴う左室駆出率低下型心不全および右脚ブロック患者における心伝導系ペーシングは、心機能、心筋仕事量、および身体能力を改善した

Background/Objectives: Conduction system pacing (CSP) is a potential alternative to biventricular pacing (BVP) in heart failure with reduced ejection fraction (HFrEF) and left bundle branch block (LBBB) or non-LBBB. Available data also suggest that unlike BVP, CSP may improve clinical outcome in patients with right bundle branch block (RBBB), although its effects on cardiac mechanics and energetics are ill-defined. Herein, we report on echocardiographic and clinical outcomes of CSP in this patient cohort. Methods: CSP either with His bundle pacing or LBB area pacing was attempted as a primary strategy in patients with RBBB, QRS duration ≥ 130 ms, LVEF < 35% and NYHA II-IV symptoms after optimized medical therapy for 6 months. Data on functional status, NT-proBNP and echocardiographic parameters were collected at baseline and 6 months after CSP. Results: CSP performed in 16 patients reduced QRS duration from 155.3 ± 12.8 ms to 130 ± 16.5 ms (p < 0.001), increased LVEF from 27 ± 7% to 33 ± 9% (p = 0.01), improved LV global longitudinal strain from -7 ± 3% to -10 ± 4% (p = 0.004) and improved LV peak strain dispersion from 126 ± 28 ms to 96 ± 23 ms (p = 0.004). Global myocardial work index increased from 582 ± 277 mmHg% to 840 ± 306 mmHg% (p = 0.003), as did global constructive work (900 ± 374 mmHg% to 1203 ± 393 mmHg%; p = 0.006) and global work efficiency (from 71 ± 7% to 77 ± 8%; p = 0.004). NYHA class (12.5% with NYHA II, 87.5% with NYHA III before vs. 25% with NYHA I, 50% with NYHA II and 25% with NYHA III at 6 months; p = 0.002) and 6 min walk distance (from 354 ± 88 m to 411 ± 95 m; p = 0.003) improved, while NT-proBNP decreased (from 4093 ± 7215 ng/L to 2087 ± 2872 ng/L, p = 0.003). Conclusions: CSP improved functional capacity and echocardiographic parameters related to cardiac functions and myocardial work in HFrEF patients with RBBB. Nevertheless, these results await further confirmation by large-scale, multi-center randomized trials.