High Blood Pressure
HYPERTENSION (HIGH BLOOD PRESSURE)
Provides an overview of this common and important problem
- Hypertension is a major risk factor for stroke and heart attacks
- The risk can be substantially reduced by attention to lifestyle issues
- Medication has been shown to be safe and effective at reducing complications if pressures remain elevated.
- Undetected and under-treated hypertension remains unfortunately common.
What is blood pressure?
Everyone has a blood pressure - in fact it is this pressure which makes the blood circulate through the body’s arterial system. Blood pressure fluctuates throughout the course of the day - it goes up during exercise and intense activity and is lower at rest and particularly lower during sleep.
How is it measured?
It is important that you are feeling rested and not rushed or stressed when having your blood pressure recorded.
A cuff is inflated over the arm and blown up; the pressure on the arm blocks the arterial pulse. As the pressure is let down, jets of blood start getting through the artery (this is heard through the stethoscope).
The point at which these sounds are first heard is called the systolic blood pressure and is the reading on the top. The pressure is recorded in millimetres of mercury as this is what is in the column that measures the pressure reading.
As the pressure in the cuff goes lower, the pulsing sounds get fainter and fade away; the point at which they fade away totally is known as the diastolic blood pressure and is the bottom reading.
Both the top and bottom readings are important in determining the risks of high blood pressure.
For example a pressure of 120/80 means the systolic pressure is 120 and the diastolic is 80.
It is important that the correct sized cuff is used - if you have a bigger arm a larger cuff is needed, otherwise a reading may be falsely too high.
Because blood pressure varies so much, it is important to have it checked several times. If the pressure is high, it should be rechecked several times over a period of time.
If it is very high (e.g. 180/110), it should be checked sooner (within days or weeks), but if it is only just above normal (e.g. 145/95), it is fine to check it in a few months.
Automated home blood pressure machines are also increasingly used. If these are used it is important that they are reliable and accurate (your doctor may be able to guide you).
Increasingly, ambulatory blood pressure monitoring may be used to gain a better picture of what a blood pressure is actually doing. A cuff is worn for 24 hours and a series of recordings is made, including during sleep. It is particularly useful in cases where blood pressure is very labile (up and down) and where it is in a borderline category (where treatment decisions may be more difficult).
It may also be useful to help establish which patients may just be getting an "alarm response" (pressure goes up when being measured).
High blood pressure should not be diagnosed until there have been consistent high measurements on several occasions.
What is normal?
Levels around 130/80 and below are absolutely fine. Doctors are generally concerned when levels are consistently greater than 140/90, as this is the level above which blood pressure starts significantly contributing to the long term risk of increased cardiovascular problems (strokes and heart attacks).
Depending on the exact classification used, pressures around 140-150/90-100 would be called mild hypertension. Pressures around 150-170/100-110 would be called moderate, and pressures higher, e.g. 200/120 would be considered fairly severe.
In reality blood pressure is a continuum, and it is sometimes difficult to be categorical about exactly what category a person is in. The higher the pressure is, the greater the risk that it will lead to further problems.
Causes of high blood pressure
The exact cause of most (90-95%) cases of high blood pressure remains unclear. It is probably caused by a mixture of lifestyle and dietary factors in people who have a genetic tendency.
In a smaller group of patients, a single underlying condition may be responsible - this is more likely to be the case in a young person with very high blood pressure and none of the usual lifestyle risk factors. Such cases are referred to as secondary hypertension. They can usually be identified by careful examination and additional tests if indicated.
Important factors in Essential Hypertension
The following factors all play a role in essential hypertension and correcting them as far as possible, plays a very important role in the lifestyle treatment of high blood pressure.
The tendency to high blood pressure runs in families. If you have a parent with high blood pressure, it is important to make lifestyle changes from a young age and have your blood pressure checked regularly every few years. Often it may only start increasing from middle age onwards.
African Americans seem particularly prone to hypertension and its effects.
This is probably one of the main areas where lifestyle changes can be most effective and lead to substantial improvements in blood pressure levels.
There is no doubt that being overweight may bring on hypertension. The exact mechanism is unclear but may involve increased peripheral resistance and metabolic changes.
A high salt diet may increase the tendency to hypertension in some people - this is thought to be a factor in approximately 40% of people with hypertension. The exact mechanism is unclear.
There is some evidence suggesting that a high dietary potassium intake will reduce the risk of hypertension. Fruit tends to have high potassium content and is the best source of dietary potassium.
A good calcium intake has been linked to hypertension and recent research has showed a high calcium diet (low fat dairy food) may help reduce high blood pressure.
The renin-angiotensin system
It is thought that abnormalities in the hormonal system in the kidney may lead to the production of chemicals (angiotensin) which brings on hypertension.
The exact mechanism remains unclear as does its importance in individual patients.
Excess alcohol (e.g. greater than 2-3 drinks a day) is a very important factor in many cases of high blood pressure. The exact mechanism by which alcohol increases blood pressure is uncertain, but it is believed to be a major factor in a substantial portion people with essential hypertension. It also leads to difficulty controlling it and resistance to the effects of medication.
Very modest drinking (1-2 drinks a day) may be beneficial for the heart - the key is the amount that is drunk!
This includes specific medical conditions which lead to hypertension as a result of the underlying illness/condition and include the following. Secondary causes account for only about 5% of cases of hypertension, but they are worth considering as they may be cured by treating the underlying cause. A secondary cause may be more likely in a young person with very high blood pressure.
Conditions which damage the kidneys, such as previous infection/reflux, polycystic kidneys may lead to hypertension.
Increasingly, renal artery stenosis (narrowing of the kidney artery) is being recognised as an important cause of hypertension.
Hyperthyroidism - an overactive thyroid gland may cause raised blood pressure.
Phaeochromocytoma - this is a very rare problem, where adrenaline-like chemicals are secreted by a tumour in the adrenal gland; some cases are associated with headache, sweating and palpitations.
Hyperaldosteronism - this results from the secretion of a chemical called aldosterone by the adrenal gland. A clue to this condition may be a low potassium level in the blood.
Cushing's syndrome - this is from a variety of conditions which result in an increased production of cortisol (a steroid, either from tumours or problems in the adrenal gland). Features include truncal obesity, striae (stretch marks in skin), hirsuitism (excess hair).
This is characterised by loud snoring, which may be followed by apnoea (no breathing) and then gasping or snorting. The changes and stress this puts on the body may lead to high blood pressure. Daytime sleepiness may be a feature and morning headaches.
Special sleep studies (a polysomnograph) is needed to diagnose it.
Medications and drugs
Several medications may cause or aggravate hypertension including:
- Non-steroidal anti-inflammatories
- Illegal drugs such as cocaine and amphetamines may cause dramatic increases in blood pressure.
Why is high blood pressure so important?
Although high blood pressure usually causes no symptoms at all, it acts as a major cardiovascular risk factor over time. Having high blood pressure substantially increases the risk of having a stroke or heart attack in the future.
As a high proportion of people will eventually suffer from some form of cardiovascular disease, it is an important public health issue to try and reduce the risk of this.
The actual risk of an actual problem occurring in a younger person is usually small, but if blood pressure remains elevated, it will continue increasing the risk of future events such as heart attacks and strokes.
The risk associated with high blood pressure increases with age and is further increased in the presence of other risk factors such as smoking, high cholesterol and diabetes.
The following specific conditions are specifically related to high blood pressure:
Coronary heart disease
Hypertension is an important risk factor for heart attacks. Having high blood pressure may double the risk of a heart attack. The risk of heart attacks is further increased if other risk factors are present. Treating high blood pressure reduces the risk of heart attacks substantially (approximately 20 %). This risk is further reduced if other risk factors are also treated.
The reasons that treating high blood pressure does not lead to as great a reduction of heart attacks and stroke, are not well understood.
In patients who have already had a heart attack, it is vitally important to gain good control of blood pressure to try and help reduce the risk of further problems.
Congestive heart failure
Many elderly people develop congestive heart failure - this may be as a result of heart attacks damaging the heart muscle, or as a result of years of uncontrolled hypertension placing undue stress on the heart muscle.
Hypertension is a major risk factor for all types of stroke, and effectively treating it can reduce the risk by approximately 30-40 percent.
Hypertension may lead to kidney damage. If there is already a kidney problem (e.g. due to diabetes), hypertension will accelerate the damage.
In the presence of kidney failure or even mild kidney impairment, it is vitally important to control hypertension, to minimise ongoing kidney damage.
The small vessels at the back of the eyeball can sometimes be damaged by raised blood pressure leading to visual problems.
What symptoms does high blood pressure cause?
The vast majority of people with hypertension have no symptoms at all and in fact would have no idea at all that their blood pressure was raised, unless it was measured. This is why it is sometimes referred to as the "silent killer".
Feelings of tension and stress are not automatically linked to high blood pressure and many people with high blood pressure are in fact perfectly calm and relaxed.
This is why some people may find it difficult to accept that there may be a potential problem, as they feel absolutely normal.
Very rarely a condition called malignant hypertension is associated with extremely high pressures and headache may be a feature of this.
For the vast majority of people with high blood pressure, headaches are not a feature of the condition.
However, a painful headache (like anything painful) may cause a slight increase in blood pressure.
Often the symptoms are of complications of the long term effects of hypertension e.g. angina, strokes and heart failure.
Examination is usually geared towards confirming the blood pressure on several occasions. The heart and general circulation needs to be examined well and signs of rare conditions will usually be checked for by doctors. This is especially so in cases of very high blood pressure in young patients, who will be more likely to have an underlying cause (secondary hypertension).
Investigations and tests
These are important to check for other risk factors such as diabetes (sugar) and high cholesterol (lipids).
Other blood tests are needed to exclude kidney problems and other hormonal problems mentioned.
Urine tests - testing of the urine is needed to exclude an underlying kidney problem.
An ECG (electrocardiogram) and chest X-ray are often ordered as part of diagnosing an enlarged heart or other underlying heart problems.
An echocardiogram (echo) is a useful test to tell accurately whether the heart muscle is enlarged or thickened (this may indicate a need for specific or more urgent treatment).
The aim of treatment is not just to simply lower blood pressure, but to actually substantially reduce the risk of heart attacks and strokes and other circulation problems and make the person live a longer healthier life. If the best results are to be achieved, it is vital that all the vascular risk factors are treated e.g. lowering cholesterol and giving up smoking will add a substantial further benefit to any blood pressure treatment.
In general, lifestyle measures should be tried first before considering medication. For example a young person (say around 40) with mild hypertension (of around 143/92) and no other risk factor would be advised to vigorously try lifestyle changes for possibly up to a year, before considering medication.
If there were other problems such as a previous heart attack, diabetes or very high cholesterol, a move to medication would likely be advised earlier.
Regardless of whether medication is tried either initially or later, lifestyle changes have a great impact and should be continued.
Stopping smoking. This is probably the most important, as smoking is such a powerful vascular risk factor (for both heart attack and stroke) and greatly increases the risks associated with high blood pressure.
Diet.The key issue is to have a healthy low fat diet which results in a gradual weight loss. The help of a dietician should not be underestimated to help with a programme and support to achieve this. A very high proportion (over 50 %) of overweight patients may be able to control blood pressure with weight loss alone. As a general rule of thumb, each pound of weight loss can result in a 1mm Hg reduction of blood pressure. This means many overweight people could avoid the need for medication altogether by achieving a modest weight loss of 10-15 pounds.
Achieving as close to possible a normal weight is highly desirable.
Sodium. Very low salt diets are not very well tolerated, but it is wise to have moderate salt restriction. For example do not add a lot of salt and avoid very salty foods. Most dietary sodium comes from meats (including poultry and fish), grains and dairy foods, so being overly restrictive could have adverse effects on overall nutritional needs and is probably not necessary.
Potassium - in practice this means eating plenty of fruit (aim for five pieces per day and vegetables).
Exercise - regular exercise has been shown to lower blood pressure and will also help with weight loss. If you are not used to exercise, it is best to start gradually and increase slowly. Exercise can be gentle and yet still beneficial - aim for the equivalent of 30-45 minutes per day on most or all days of the week.
It is wise to be evaluated carefully if there are risk factors before undertaking any vigorous programme of exercise, particularly if you are over the age of 40. An exercise test may be advised as a precaution in some cases.
If blood pressure levels remain elevated despite lifestyle changes, medication may be needed and discussed with your doctor. There is pretty unanimous agreement amongst doctors that drugs should be used if blood pressure is severely elevated e.g. 160/100 at age 20, 160/110 at age 50.
In fact there is good evidence that treating even mild hypertension with medication is beneficial e.g.160/95 at age 50 is effective in reducing complications like stroke.
In patients at greater risk because of other risk factors, medication may be started at relatively lower levels e.g. 140/90.
Such patients may include those with diabetes, previous heart attack or stroke, high cholesterol and heart failure: In such patients, the baseline risk of further problems is much higher, so treatment is relatively more beneficial.
It has been shown that it is beneficial to treat isolated systolic hypertension (e.g.165/85), where only the top level is elevated.
Trials have also confirmed that it is beneficial to treat hypertension in older people as well. In fact it may be particularly beneficial as the risk of problems increases with age.
The aim of medication is to reduce blood pressure with minimal side effects and inconvenience. All medications may take a month or two to exert their full effect, so most doctors will "start low" and "go slow" until the desired blood pressure level is reached.
There are a number of suitable and effective medications for safely lowering blood pressure and reducing the risk of complications.
The most studied over many trials include thiazide diuretics and B-blockers, which have been convincingly shown to reduce complications.
Unless there is a reason not to, most doctors will choose one of these when starting therapy.
Other classes of medications which have been shown to safely and effectively lower blood pressure include ACE inhibitors, calcium channel blockers and alpha blockers.
All these medications have pros and cons and need to be chosen for their potential benefits in a given patient.
Often a second or even occasionally a third medication may be required to achieve adequate control.
Includes drugs such as bendrofluazide and cyclopenthiazide. These are a particularly good choice in the elderly or in the presence of mild heart failure.
They may occasionally raise sugar levels or precipitate gout. These side effects are rare at low doses which have been found to be particularly effective.
Beta-Blockers (B-adrenoreceptor blockers)
These include drugs such as propanolol atenolol, metoprolol, celiprolol and pindolol.
These are effective drugs which have been well researched. They should not be given to patients with asthma as they may aggravate it.
They are particularly useful in patients with angina or patients who have had a previous heart attack (they have been shown to improve survival in these patients).
Ace Inhibitors (angiotensin converting enzyme inhibitors)
These include drugs such as captopril, enalapril and quinapril. They have been shown to safely and effectively to lower blood pressure with minimal side effects. Care is needed to check kidney function while taking them, especially when starting or altering the dosage. They may cause an irritating cough in a small percentage of patients.
These drugs may be particularly useful in diabetic patients, particularly where there is associated kidney damage and proteinuria (protein in urine).
They are also particularly useful after a heart attack where there has been significant muscle damage.
They are also useful for the treatment of heart failure and are the treatment of choice if there is significant heart failure associated with hypertension.
These include drugs such as such as verapamil and nifedipine. They are generally not used as a first line treatment, but they have a useful role in certain patients (e.g. angina) and where other medications are not tolerated.
Alpha Adrenergic blockers
Includes drugs such as prazosin. These are used less nowadays, but may continue to have a role in certain patients.
Other drugs used to reduce risks
Recent studies have indicated that it may be beneficial to add low-dose aspirin to treatment of hypertension (once the blood pressure is controlled). There may be reasons why some patients cannot take aspirin (e.g. previous ulcer), so patients should always discuss this with their doctors.
Goals of treatment
To reduce the risk of complications, it is wise to aim for levels below 140/90. It may take some time to achieve this. Unfortunately a high percentage of people taking medication do not achieve these goals, so it is important to have regular checks and adjustments in treatment until the goal is reached. This will require ongoing lifestyle changes and possibly trying several different medications or combinations. This is because sometimes the different classes of medication work better for some people than others.
There is some evidence that pressure does not need to be lowered too much below 140/85 - the exception to this is in the presence of diabetes, where the aim should be 130/80.
It is very important to have frank and honest discussions with your doctor about compliance (taking medication), alcohol intake and side effects as these are major issues which may prevent patients achieving good blood pressure levels.
Fundamental research is continuing into the causes of high blood pressure and research and development of effective treatments.
However, it is worth remembering that the situation could be greatly improved by applying more effectively what we already know.
A very high proportion of people with hypertension are not even detected (35%). Of those who are detected, only half are taking medication and 80% of those may still have blood pressures over 140/90.