High Blood Pressure (Hypertension)
Causes of Hypertension
The World Health Organization’s criterion for a diagnosis of hypertension is a blood pressure of 160/95 mmHg or greater. Pressures between this and 140/90 are borderline. Most physicians treat diastolic pressures of 95 mmHg. Three readings are usually recorded over several days before treatment is begun. Factors such as anger, anxiety, stress and exercise may cause a transient increase in blood pressure so the person should rest for several minutes before the blood pressure is taken.
In most cases (95%) the cause of hypertension is unknown (primary or “essential” hypertension). A genetic component appears to be present involving excessive sensitivity to dietary salt and an overstimulation of the sympathetic nervous system. The overstimulation of sympathetic activity causes arteriolar spasm which creates hypertrophy of the muscle layer of the arteriole, narrowing of the vessel, and an elevation of the blood pressure. The baroreceptor mechanism is reset to a higher level. The kidney appears to be involved.
Weight reduction, salt restriction, and the discontinuance of alcohol and smoking. A stepped-care approach is often used: the patient is started on a diuretic, beta-blocker or calcium-channel blocker, and other agents are added as needed, such as one of the above or an angiotensin- converting enzyme (ACE) inhibitor.