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Patient
63-year-old man with primitive dilated cardiomyopathy;
Trace
Sinus rhythm, normal PR; complete left bundle branch block: QRS width > 120 ms (152 ms); absence of an exclusive q wave and R wave, wide and notched in leads I, aVL, V5 and V6 with a delayed intrinsicoid deflection > 60 ms; QS and rS pattern in V1 and V2; ST segment depression in leads I, aVL; ST segment elevation in V1-V3; negative T-wave in leads I, aVL, V5 and V6;
Patient
24-year-old man, asymptomatic;
Trace
Sinus rhythm, typical pattern of complete right bundle branch block: QRS duration of 130 ms; V1: rSR' pattern, delayed intrinsicoid deflection, negative T-wave; V6: qRS pattern with septal q wave and wide slurred S wave;
Exergue
The left bundle branch block is characterized by a disturbance of all ventricular depolarization vectors; the right bundle branch block is characterized by a disturbance of the vectors of the second part of the QRS; activation of the left ventricle is normal, hence explaining the normality of the vectors of the first part of the QRS.
The bundle branch block corresponds to a slowdown (incomplete block) or an interruption (complete block) of the path of the ventricular excitation wave in the conduction pathways below the bifurcation between the right branch and left branch.