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The difference between the normal narrow QRS and wide QRS as seen in left bundle branch block (LBBB) and right bundle branch block (RBBB). Also note the relative contribution of the left ventricle (LV) and right ventricle (RV) to the QRS complex. (Source: University of San Francisco, http://www.usfca.edu/fac-staff/ritter/section.htm. Reprinted with permission.)
