High blood pressure

Blood pressure varies throughout the day. In particular, it increases during exercise and decreases during sleep. Though hypertension can cause headaches, dizziness and visual disturbances, the majority of patients do not suffer from any symptoms. Hence the condition may remain undiagnosed. Having a routine blood pressure check is recommended or more comprehensively, a 24 hour ambulatory blood pressure monitor (ABPM) to give a more accurate picture of blood pressure levels and variation.

Blood pressure is measured in millimetres of mercury (mm Hg) and consists of two readings, e.g. 120/80 mm Hg. The systolic pressure is the first number that represents the force of the blood during contraction of the heart as it pumps blood around the body. The upper limit of normal is usually defined as 140 mm Hg. The diastolic pressure is the second number that represents the pressure in the arteries of the body while the heart is relaxed, preparing for the next contraction. This is always lower than the systolic pressure and has an upper limit of 90 mm Hg.

If hypertension is diagnosed, an underlying cause should be sought, especially when the blood pressure is particularly high or the patient is young. In 90% of cases however, the cause is unknown and the condition is termed primary hypertension. If a cause is identified, e.g. an underlying problem with the kidneys, adrenal glands or aorta, it is termed secondary hypertension and on correction of the problem, the high blood pressure usually returns to normal.

If primary hypertension is left untreated or is combined with obesity, smoking, high blood cholesterol levels or diabetes, the risk of a heart attack is several times higher. The reason for this is that arteries become harder and lose their elasticity over time, leading to the build up of cholesterol. This process is called arteriosclerosis and results in a narrowing of the blood vessel. Arteriosclerosis is accelerated by hypertension with the overall effect of a reduction in the blood supply to an organ, preventing them from working effectively and leading to problems such as heart attack, stroke, kidney failure, retinopathy and peripheral vascular disease.

A healthy lifestyle can help reduce blood pressure when mildly elevated (140/90 mm Hg). This includes a reduction in salt intake, regular exercise, not smoking and having a low-fat diet. Medication for hypertension is usually recommended when the blood pressure remains elevated despite lifestyle measures or in those who have pre-existing cardiovascular disease or diabetes. Your cardiologist will usually recommend the appropriate medication and liaise with your GP to achieve the best possible blood pressure control.