Figure 1: ECG Strip[1]
A left bundle branch block occurs when "the normal direction of septal depolarization is reversed (becomes right to left), as the impulse spreads first to the RV via the right bundle branch and then to the LV via the septum."[2] The reversed direction of depolarization produces deep S waves in the right precordial leads (V1) and tall R waves in the lateral leads (V6).[2]
Table 1: ECG Characteristics[3]
Figure 2: ECM Analysis, Record 109[5][6]
Additional Example of a LBBB
Figure 3: Record 214[5][6]