Factors determining the magnitude of the pre-ejection leftward septal motion in left bundle branch block

Abstract

Left bundle branch block lowers afterload against pre-ejection septal contraction, expressed as slowed rise of P_LV-RV, which is a main cause and determinant of the magnitude of leftward septal motion. The motion may be small or absent due to septal infarct, impaired global or RV contractility or RV volume overload, which should be kept in mind if this motion is to be used in evaluation of CRT response.