The World Health Organization (WHO) has defined the term hypertension as, “a persistent elevation of the systolic blood pressure above 140 mmHg and diastolic blood pressure above 90 mmHg.†The blood vessel type that is being measured in this case is the arterial pressure. When systemic arterial blood pressure is elevated, this indicates that the heart is working harder than it should to be able to pump the blood throughout the whole body. The normal value of blood pressure is 120/80 mmHg in adults.