True complete left bundle branch block reveals dyssynchrony evaluated by semiconductor single-photon emission...

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.