It causes the heart to work harder than normal putting both the heart and arteries at greater risk of damage. High blood pressure, or hypertension, increases the risk of heart attacks, strokes, kidney failure, damage to the eyes, congestive heart failure and atherosclerosis.
Hypertension exists where the pressure at which blood is pushing against blood vessel walls is consistently above average.
Blood pressure changes throughout the day. In particular, it increases during exercise and decreases during sleep.
Untreated high blood pressure can cause the heart to become abnormally large and less efficient (ventricular hypertrophy) causing heart failure and increased risk of heart attack.
Although high blood pressure can cause headaches, dizziness and problems with vision, the majority of people suffer no symptoms at all. As a result many people with hypertension remain undiagnosed because they have no symptoms to motivate them to see a doctor or get their blood pressure checked.
However, despite the lack of symptoms hypertension can lead to heart attack, stroke, kidney damage, and many other medical problems
In over 90 per cent of cases, the cause is unknown. In the remaining cases, high blood pressure is a symptom of a recognisable underlying problem such as a kidney abnormality, tumour of the adrenal gland or congenital defect of the aorta (in these cases when the root cause is corrected, blood pressure usually returns to norma).
This type of high blood pressure is called secondary hypertension.
If high blood pressure isn’t treated and is combined with obesity, smoking, high blood cholesterol levels or diabetes, the risk of heart attack is several times higher.
Arteries also suffer the effects of high blood pressure, becoming scarred, hardened and less elastic. Though this hardening of the arteries often occurs with age, high blood pressure accelerates the process. The hardened or narrowed arteries are unable to supply the amount of blood the body’s organs need, preventing them working effectively. Another risk is that a blood clot may lodge in an artery narrowed by atherosclerosis, blocking blood supply.
The only way to find out if you have high blood pressure is to have your blood pressure checked. A doctor or other qualified health professional should check a patient’s blood pressure at least once every two years.
It’s measured in millimetres of mercury (mm Hg) and is defined in an adult by the recording of two readings:
- Systolic pressure – represents the force of the blood as the heart contracts (beats) to pump it around the body. This is the higher of the two readings and records blood pressure at or above 140mm Hg.
- Diastolic pressure – the pressure while the heart is relaxed and filling with blood again in preparation for the next contraction or heart beat. This value is lower than the systolic pressure and records blood pressure at or above 90mm Hg.
What is considered to be an acceptable blood pressure and what is hypertension (and then what needs treatment) depends on several factors. A single high reading isn’t enough to warrant a diagnosis of hypertension as blood pressure can be raised in all of us now and then – even the sight of a doctor can be enough to put it up. So there must be at least three high readings to cause concern.
When high blood pressure is first diagnosed, tests may be done for an underlying cause (i.e. secondary hypertension) especially if the person is young or has very high blood pressure. If an underlying cause is found it should be treated.
There’s no cure as such for essential hypertension, but following a healthy lifestyle can be enough to bring blood pressure down to a normal level. This is one reason why drug treatment may not be offered for healthy individuals with only mild hypertension (above 140/90 mmHg but below 160/100 mmHg).
Medication is used if lifestyle changes alone fail to lower blood pressure sufficiently. It’s generally recommend that drug treatment is offered to those with:
- Blood pressure above 160/100 mmHg
- Isolated systolic hypertension of more than 160 mmHg
- Blood pressure of more than 140/90 mmHg (ie, mild hypertension) but who also have cardiovascular disease or significant risk of developing cardiovascular disease, diabetes, or damage to the heart, kidney or eyes as a result of high blood pressure
Current UK guidelines also recommend that blood pressure levels need to be even lower for certain people and say treatment should aim to lower blood pressure to below 130/80 if a person has:
- A complication of diabetes, especially kidney problems
- Had a serious cardiovascular event such as a heart attack, TIA or stroke
- Has certain chronic kidney diseases
All medicines can have side effects and sometimes it’s necessary to try different drugs if initial treatments cause problems.