Dr Idris Harding:
Private cardiologist in West Kent

Blood pressure measurement allows the diagnosis of hypertension (high blood pressure) and can be used to assess how effective treatment of hypertension is. Blood pressure readings can also inform assessment of the risk of stroke and heart attack.

Usually, blood pressure is taken via a one-off reading either in the doctor’s surgery or at home.

The usual technique is to sit quietly for 5-10 minutes and then take the blood pressure three times. The lowest measurement of the three is recorded.

Some people get very anxious about having their blood pressure taken and this can cause artificially high blood pressure readings (so-called “white coat hypertension”). If you or your doctor suspect this is affecting your readings then it can be useful to use a machine that automatically takes the blood pressure many times over 24hrs to reach a more accurate view of the blood pressure over time.

Having a 24hr blood pressure monitor (also called an “ambulatory blood pressure monitor”) should be a painless and unintrusive experience. The monitor is fitted around your arm like a normal blood pressure cuff during a clinic visit and you will be given a small recording unit to carry around with you, usually with belt loops or a lanyard to make it easier to carry.. After wearing the monitor for a day and a night it is returned to the clinic for analysis.

Very occasionally the repeated blood pressure measurements can be uncomfortable or mildly painful in which case the test is less useful as artificially high readings are likely to be made. This is not common but if it happens to you then your doctor may suggest other ways to assess your blood pressure.

Magnetic Resonance Imaging (MRI) is now a common investigation to look at the heart. It is particularly useful for examining the substance and function of heart muscle. In comparison to echocardiography, for instance, MRI can offer unrestricted views of part of the heart that can be difficult to see with echo, and MRI also gives information on the makeup of cardiac muscle including the presence of scarring. This information tends to be more limited on echo scans.

The pattern of scarring in heart muscle can be used to determine the cause of heart diseases.

Some heart muscle diseases (“cardiomyopathies”) have very characteristic scar patterns on MRI, and the diagnosis can be made with high certainty from this one test. For some other conditions the scar pattern can be suggestive but not conclusive, and for these diseases other tests including echo, ECG recordings, angiography and blood tests are used to build a fuller picture of the disease.

To accentuate the difference between types of tissue, some MRI scans are performed with an injection of contrast medium into the vein during the scan. The most common contrast agent used is Gadolinium. This is generally a very safe drug; allergic reactions are very rare. Gadolinium can affect kidney function, however, and it is generally avoided for patients with pre-existing severe kidney impairment.

MRI scanning uses strong magnets and for this reason some people with metal implants (eg: some joint replacements) or metal fragments embedded in the bodies from accidents, cannot have MRI scans due to the risk of dislodging these during the scan. You should be given a safety questionnaire to complete before any MRI scan.

Some cardiac devices (pacemakers, defibrillators, etc) are safe in MRI scanners, and some are not. This is assessed on a case by case basis.

Not all cardiac MRI scans are the same: different sequences of pictures will be obtained depending on the question being asked. It is unusual for scans to last less than 30 minutes, or more than 90 minutes.

Most MRI scanners are fairly confined spaces. People with severe claustrophobia may have difficulties completing the scan but this can usually be planned for.

Stress tests examine how the heart copes during exercise. This can help find out whether symptoms that come on during exercise, for example chest pain or palpitations, are due to heart disease. These tests are particularly useful for diagnosing ischaemic heart disease. The tests can also be used to judge the severity of heart valve disease if other tests have been inconclusive.

The most straightforward stress test is a Bruce protocol exercise test. This involves walking then running on a treadmill that gets faster and steeper every two minutes. An ECG is recorded before and during exercise to examine for electrical changes brought on by exertion. The protocol can be modified to make the exertion easier for people less able to run, but these days alternative tests are also available.

During an exercise echocardiogram, ultrasound pictures of the heart are taken at rest and while peddling on a recumbent bicycle or other exercise equipment. This is generally more tolerable to patients with some mobility problems.

If mobility problems are severe, then drug-induced stress may be used instead of exercise. Drugs such as Adenosine (to dilate the blood vessels) and Dobutamine (to speed the heart up) can be used to mimic the effects of exercise on the heart. Drug (“pharmacological”) stress can be used along with echocardiography to image the heart, or with MRI scanning to get similar information. The choice between whether to use echo or MRI for a pharmacological stress test often comes down to which technology is more readily available and where information about heart valves is also needed (in which case echo is preferable) or whether information about heart scarring would be more useful (in which case MRI might be preferred).

Ischaemic heart disease causes narrowings in the arteries over the surface of the heart (“coronary arteries”) and is the number 1 killer globally. In the UK over 400,000 deaths annually are due to the disease.

Coronary artery disease can be detected by a number of different tests including various different stress tests, but only an angioram can determine the precise site and severity of arterial narrowings.

Angiography can be carried out in two ways: invasive coronary angiography and CT coronary angiography.

Invasive coronary angiography involves passing wires and tubes through the artery in the arm or leg, to the heart, and injecting X-ray dye directly into the coronary arteries, while short X-ray videos are taken. This is done after administration of local anaesthetic to the arm or groin area, and sometimes under light sedation. This test is done in a special operating theatre called a catheter laboratory (“cath lab”) and generally patients undergoing invasive angiography stay in hospital a few hours after the procedure and go home the same day.

CT coronary angiography gives a larger dose of X-ray dye into a cannula in the arm. A CT scan is then acquired to see the dye entering the coronary arteries. No wires or tubes are placed inside the body except for the small arm cannula. This test is generally done in the radiology department and patients go home immediately, or very soon after the procedure.

The decision whether to use CT or invasive coronary angiography depends on many factors. The main advantages of invasive angiography are that it allows treatment (e.g.: stenting) to be carried out at the same time as he diagnosis is made, and it may involve giving less X-ray dye and less X-ray dose than CT. However, unlike CT, invasive angiography involves direct access to the main arteries around the heart and thus it carries a higher complication risk.

Many patients are offered a CT angiogram initially to diagnose coronary narrowings, and then an invasive angiogram happens later as part of a stenting procedure.

Every heartbeat is caused by a series of electrical changes in the heart, which trigger the heart muscle to contract in an organised and coordinated way.

The standard ECG gives a 10 second snapshot of the electrical activity of the heart and allows diagnosis of persistent electrical abnormalities within the heart including ongoing tachycardias, bradycardias and arrhythmias.

Some heart muscle diseases (cardiomyopathies) cause characteristic changes to the electrical activity of the heart and the ECG can therefore be helpful in diagnosing these conditions. In heart failure, the ECG can determine whether certain treatments are likely to be successful.

Having an ECG is a painless and safe procedure. Stickers are fixed to the arms, legs and chest and you will be asked to lie still for a few seconds to allow the recording to be taken. People with a lot of body hair may need to have part of the chest shaved to allow the recording to be taken.

Many cardiac diseases including ischaemic heart disease, rhythm disturbances (“arrhythmias”) and heart valve disease can affect the pumping capacity of the heart.

Echocardiograms (sometimes called “echos”) are a simple and safe way to examine the structure and function the heart. Generally, echo can give excellent assessments on the size and motion of heart muscle, heart valves and parts of the large arteries and veins that lead out of the heart pumping chambers.

Having an echo scan is very similar to having any other medical ultrasound examination. This involves lying still while a technician uses a small ultrasound probe on the chest to take pictures of the heart. Ultrasound jelly is used on the chest to improve the quality of the pictures. The pictures are also affected by movement, so you may be asked to adopt different positions during the scan. Most echos are done with the patient lying slightly propped up and slightly rolled onto the left hand side - this tends to give the best views of the heart. You may be asked to alter your breathing pattern during the scan or to hold your breath for short periods to help get the best pictures.

Sometimes echo picture quality is reduced due to lung disease or other reasons preventing sound waves from reaching the heart. In these cases a cannula may be sited in the arm and an injection of contrast medium given to help show up the heart chambers better on the echo scan. Very rarely, even doing this fails to improve the picture quality, so that another test might be suggested instead.

Because echo uses only ultrasound waves it is a very safe test. No radiation is involved. Allergic reactions to the echo contrast medium are possible (if used) but these are not common.

Many heart rhythm abnormalities (“arrhythmias”) are intermittent. The only way to reliably diagnose these problems is to record the electrical activity of the heart (an “electrocardiogram”) during an episode of the problem.

There are now many ways to do this, with various different consumer devices available. However in many cases the gold standard test remains the ambulatory ECG.

Ambulatory ECG devices generally include between one and three electrical leads fixed to the chest wall with stickers (“electrodes”). The ECG is recorded by a small computer, generally carried in a pouch with belt loops, or on a lanyard. Some newer devices are so small that no separate computer unit is required, and the whole recorder is stuck to the chest wall.

An ambulatory ECG can last between one and 14 days. During that time it is important to record any symptoms. Different devices include different ways of tagging symptoms: most modern devices include a button on the device or a smartphone app that allow you to record a time stamp. With older devices you may simply be asked to make a written record of the time and date that any symptoms were felt. It is important to be as accurate as possible with these manual records, as the times you record will be used match up your symptoms with what the heart rhythm was doing at the time.

At the end of recording the device is returned for analysis, either to your local hospital or via courier to an analysis centre. The first stage of analysis is generally automated but most services also include manual verification of the findings to ensure that important or dangerous arrhythmias are not missed, and that all findings are correctly described to your consultant.