Comparison of Echocardiographic Markers of Cardiac Dyssynchrony and Latest Left Ventricular Activation Site in Heart Failure Patients with and without Left Bundle Branch Block

Several echocardiographic markers have been introduced to assess the left ventricular (LV) mechanical dyssynchrony. We studied dyssynchrony markers and the latest LV activation site in heart failure patients with and without left bundle branch block (LBBB). Conventional echocardiography and tissue velocity imaging were performed for 78 patients (LV ejection fraction ≤ 35%), who were divided into two groups: LBBB (n = 37) and non-LBBB (n = 41). Time-to-peak systolic velocity (Ts) was measured in 12 LV segments in the mid and basal levels. Seven dyssynchrony markers were defined: delay and standard deviation (SD) of Ts in all and basal segments, septal-lateral and anteroseptal-posterior wall delay (at the basal level), and interventricular mechanical delay (IVMD). The LBBB patients had significantly higher QRS duration and IVMD. The posterior wall was the latest activated site in the LBBB and the inferior wall was the latest in the non-LBBB patients. The most common dyssynchrony marker in the LBBB group was the SD of Ts in all segments (73%), whereas it was Ts delay in the basal segments in the non-LBBB group (48.8%). Ts delay and SD of all LV segments, septal lateral delay, septal-to-posterior wall delay by M-mode, pre-ejection period of the aortic valve, and IVMD were significantly higher in the LBBB group than in the non-LBBB group. Also, 29.3% of the non-LBBB and 10.8% of the LBBB patients did not show dyssynchrony by any marker. The number of patients showing dyssynchrony by ≥ 3 markers was remarkably higher in the LBBB patients (73% vs. 43.9%, respectively; p value = 0.044). The LBBB patients presented with a higher prevalence of dyssynchrony according to the frequently used echocardiographic markers. The latest activation site was different between the groups.