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Updated: Jan 28, 2026
High-Resolution Cardiac Positron Emission Tomography/Computed Tomography for Small Animals
Published on: December 16, 2022
True complete left bundle branch block reveals dyssynchrony evaluated by semiconductor single-photon emission
Munehiro Iiya1, Masato Shimizu1, Hiroyuki Fujii1
1Department of Cardiology Yokohama Minami Kyosai Hospital Yokohama Japan.
Insights
True complete left bundle branch block (CLBBB) indicates more severe heart dyssynchrony but does not predict heart failure hospitalization or cardiac death compared to conventional CLBBB criteria.
Area of Science:
- Cardiology
- Medical Imaging
- Electrophysiology
Background:
- Conventional complete left bundle branch block (CLBBB) criteria can lead to false-positive dyssynchrony diagnoses.
- True CLBBB criteria aim to better identify responders for cardiac resynchronization therapy (CRT).
- The correlation of true CLBBB with dyssynchrony severity and long-term prognosis remains unclear.
Purpose of the Study:
- To investigate the association between true CLBBB criteria and the severity of left ventricular dyssynchrony (LVD).
- To evaluate the predictive value of true CLBBB for LVD and long-term clinical outcomes.
- To compare LVD severity in patients with true CLBBB versus conventional CLBBB.
Main Methods:
- Ninety-four patients with conventional CLBBB underwent semiconductor SPECT.
- Patients were categorized into true CLBBB (defined by specific QRS duration and mid-QRS notching/slurring) and non-true CLBBB groups.
- Left ventricular dyssynchrony was assessed using SPECT parameters (bandwidth and phase SD), and multivariate analysis identified predictors of LVD. Clinical outcomes were tracked for 3 years.
Main Results:
- True CLBBB patients exhibited significantly wider bandwidth and higher phase standard deviation, indicating more severe LVD.
- No significant differences were observed between groups regarding ejection fraction, end-diastolic volume, ischemic heart disease, or summed rest score.
- True CLBBB, ejection fraction, and end-diastolic volume were significant predictors of LVD.
Conclusions:
- True CLBBB is associated with more severe left ventricular dyssynchrony as measured by SPECT.
- Despite greater dyssynchrony, true CLBBB did not predict a worse prognosis in terms of heart failure hospitalization or cardiac death at 3-year follow-up.
- The findings suggest that while true CLBBB identifies severe dyssynchrony, its prognostic implications require further investigation.
Background:
Conventional complete left bundle branch block (CLBBB) criteria sometimes result in a false-positive diagnosis that does not represent dyssynchrony. Recently, true CLBBB criteria have been proposed to detect responders to cardiac resynchronization therapy (CRT), although their correlation with severity of dyssynchrony or natural prognosis is unclear.
Methods:
Ninety-four consecutive patients (74 ± 9 years, 63 men) with conventional CLBBB during sinus rhythm underwent semiconductor SPECT. They were divided into two groups: patients with true CLBBB and others. True CLBBB was characterized by the mid-QRS notching/slurring and wide QRS duration (male, ≥140 milliseconds; female, ≥130 milliseconds). Multivariate analysis was performed to detect left ventricular dyssynchrony (LVD), defined as bandwidth ≥145° and/or phase standard deviation (SD) ≥43°. Primary endpoints (hospitalization for heart failure or cardiac death) were evaluated.
Results:
True CLBBB had wider bandwidth (145 ± 83° vs 110 ± 64°, P = 0.024) and higher phase SD (48 ± 26° vs 35 ± 19°, P = 0.007). Ejection fraction (EF), end-diastolic volume (EDV), summed rest score (SRS), and the presence of ischemic heart disease (IHD) showed no differences between groups (P = 0.401, 0.591, 0.165, and 0.212, respectively). Multivariate analysis revealed that true CLBBB, EF, and EDV were significant predictors of LVD (odds ratio, 12.6, 0.90, 1.03; P = 0.003, 0.002, 0.022, respectively). At 3-year follow-up (median 667 days), primary endpoints were comparable in both groups (log-rank, P = 0.92).
Conclusions:
Patients with true CLBBB had more severe dyssynchrony on single-photon emission computed tomography than patients with nontrue CLBBB. On the other hand, the two groups showed no differences in EF, EDV, the presence of IHD, hospitalization for heart failure, and cardiac death.
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