Correlation of LBBB and Mechanical LV Dyssynchrony in Patients with Normal and Abnormal Left Ventricular Function and Prediction of Mortality

Introduction: Patients with LBBB with symptoms of heart failure and LVEF ≤ 35% are referred according to guidelines for electromechanical resynchronization therapy (CRT) device as this has shown to improve cardiac outcome

Purpose: We studied the significance of mechanical LV dyssynchrony (MLVD) in patients with LBBB and LV function and prediction of mortality.

Methods: we selected from the database of nuclear cardiology lab, patients referred for gated SPECT MPI who had LBBB in the basic ECG. The patients were divided into 3 groups according to LVEF. All the clinical, perfusion, LV function and MLVD measured by phase standard deviation (PSD) were compared.

Results: There were 185 patients with LBBB. Group 1 included 22 patients with LVEF > 50%, group 2- 42 patients with LVEF 35%-50%. And group 3 - 121 patients with LVEF < 35%. The QRS width was 119-140 ms (95% CI), similar in all groups. However, PSD values were significantly different and increased across the 3 groups (mean values, 24, 36, 60, p< 0.0001 respectively). NYHA class prevalence (3-4) was 4%, 20%, 62% across the 3 groups of LVEF (p<0.0001). No correlation was seen between QRS width in the presence of LBBB. During median follow up of 5 years, all because deaths occurred in 4, 10 and 34 patients in the 3 groups, accordingly. In Cox regression analysis, PSD was an independent predictor for all cause mortality in patients with LVEF ≥ 35% (HR 1.030; 95% CI 1.003-1.058, p, 0.032) and for cardiac mortality as well (HR1.057; 95% CI 1.022-1.094).

Conclusions: MLVD in patients with LBBB was increasingly abnormal with correlation to LV systolic function, without correlation to QRS width. In addition to LVEF, PSD was an independent predictor of all cause mortality as well as cardiac mortality, in patients with LBBB and LVEF≥35%.