Echocardiographic demonstration of abnormal motion of the interventricular septum in left bundle branch block

A characteristic abnormality of motion of the interventricular septum was recorded by echocar-diography in 17 of 18 patients with left bundle branch block. Early and abrupt contraction of the septum occurs during the pre-ejection period before the delayed commencement of contrac-tion of the posterior wall of the left ventricle. This abnormality can be explained by asynchronous contraction of the left ventricle with early activation and contraction of the septum but delay in activation and contraction of the left ventricular free wall due to a block in the left bundle branch or its peripheral branches. Additional Indexing Words: Left ventricle Ultrasound SYSTOLIC contraction of the human left ventri-cle is normally an almost symmetrical process accompanied by small rotational movements of the chamber within the thorax. ' This pattern of contraction depends upon the normal rapid spread of myocardial activation so that the cavity is quickly surrounded by contracting myocardium during early systole.2'3 Experimental interruption of con-duction through the left bundle branch not only delays left ventricular activation but also disturbs its sequence2 so that the normal symmetry of contraction might be disturbed by asynchronous movements of the walls of the chamber. Echocar-diography has confirmed this supposition by dem-onstrating that abnormal abrupt early systolic contraction of the interventricular septum is charac-teristically found in patients with left bundle branch block