Left ventricular hypertrophy is thickening of the walls of the lower left heart chamber. The lower left heart chamber is called the left ventricle. The left ventricle is the heart's main pumping chamber. During left ventricular hypertrophy, the thickened heart wall can become stiff. Blood pressure in the heart increases. The changes make it harder for the heart to effectively pump blood. Eventually, the heart may fail to pump with as much force as needed. Uncontrolled high blood pressure is the most common cause of left ventricular hypertrophy. Complications include irregular heart rhythms, called arrhythmias, and heart failure. Treatment of left ventricular hypertrophy depends on the cause. Treatment may include medications or surgery.