Key result
Long R-R' interval in LBBB is linked to ~79% fewer adverse events after CRT.
Why the study?
The relationship among R-R' interval, mechanical dyssynchrony, viable myocardium, and long-term outcomes in CRT candidates with LBBB was not well established.
Does a long R-R' interval (≥48 ms) predict better long-term outcomes and mechanical dyssynchrony in CRT candidates with LBBB?
Cohort
Does a long R-R' interval (≥48 ms) predict better long-term outcomes and mechanical dyssynchrony in CRT candidates with LBBB?
Hazard Ratio: 0.21
p-value: p=0.014
An R-R' interval ≥48 ms on baseline ECG is a strong independent predictor of improved event-free survival, volumetric response, and mechanical dyssynchrony in CRT candidates with LBBB.
BACKGROUND: Typical left bundle branch block (LBBB) shows 2 peaks of the R wave, which reflect activation reaching the interventricular septum (R) and posterolateral wall (R') sequentially. OBJECTIVE: The purpose of this study was to investigate the relationship among R-R' interval (RR'), mechanical dyssynchrony, extent of viable myocardium, and long-term outcomes in cardiac resynchronization therapy (CRT) candidates. METHODS: , I, and aVL. Baseline evaluations were QRS duration (QRSd) and RR' measured from the 12-lead electrocardiogram; eyeball dyssynchrony (apical rocking and septal flash) and opposing-wall delay by speckle tracking from echocardiography, and extent of viable myocardium assessed by thallium-201 single-photon emission computed tomography. Primary outcomes included the combination of all-cause death and heart failure-related hospitalization. RESULTS: RR' predicted volumetric response better than QRSd (area under the curve 0.73 vs 0.67, respectively). The long RR' group (≥48 ms) revealed more frequent eyeball dyssynchrony and significantly greater radial (SL) and circumferential dyssynchrony (AP and SL) and %viable segment than the short RR' group. In multivariate regression analysis, only RR' ≥48 ms was independently associated with higher event-free survival rates following CRT (hazard ratio 0.21; P = .014). CONCLUSION: These findings suggest that RR' in complete LBBB was associated with mechanical dyssynchrony, extent of viable myocardium, and long-term outcomes following CRT.
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Kodama et al. (2023) conducted a cohort in Cardiac resynchronization therapy (CRT) candidates with complete left bundle branch block (LBBB). Long R-R' interval (≥48 ms) vs. Short R-R' interval (<48 ms) was evaluated on Combination of all-cause death and heart failure-related hospitalization (HR 0.21, p=0.014). A long R-R' interval (≥48 ms) in complete LBBB was independently associated with higher event-free survival following CRT (HR 0.21; P=0.014).
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