In left ventricular hypertrophy, there is an increase in the mass of the left ventricular free wall and the interventricular septum. This increase in ventricular mass leads to an increase in the electrical forces directed to the left and posteriorly. This is expressed electrocardiographically by an increase in the amplitude of the QRS complex. The increase in ventricular mass, coupled with intramyocardial fibrosis, increases the time required for the impulse to spread from endocardium to the epicardium which, in turn, increases the time required for left ventricular depolarization. This results in an increase in the duration of the QRS complex. In addition, primary changes in repolarization may occur, causing changes in the ST segment and the T wave.