With age, many changes occur in the cardiovascular system. There is dysfunction of the vascular endothelium, an increase in collagen and a decrease in elastin, a decrease in arterial compliance, an increase in blood pressure and a relative increase in circulating blood volume. The number of myocytes decreases and they become thickened. The mass of the left ventricle also increases. Degenerative changes of the heart valves are more common in older age.