Natural history of electrical interventricular septal force in the course of left ventricular hypertrophy in man

Initial electrical forces emanating from interventricular septal depolarization, being directed to the right and anteriorly, normally produce an initial negative deflection or Q wave in leads I, aVL and V6 and an initial positive deflection or R wave in leads V1 and V2. The observations of hypertrophied interventricular septum, an integral part of the left ventricle, in patients with left ventricular hypertrophy would predict an increase in these septal electrical forces similar to the total left ventricular (QRS) forces in these subjects. Contrary to this expectation, several studies document an actual decrease or absence of the normally oriented initial forces in ECGs of patients with the criteria of left ventricular hypertrophy. In order to clarify the nature of this paradox, this study was initiated. Our observations suggest that the normal initial septal forces indeed increase as expected, during the initial four to six years, and subsequently show a progressive decline in patients with left ventricular hypertrophy. Although the precise mechanism for the bimodal change in the septal forces during the period of the constancy of the total QRS forces is not clear, a hypothesis based on the current knowledge is advanced to explain these observations.