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Diagnosing heart conditionsThis factsheet is for people who are being tested for a heart condition. Symptoms such as angina (chest pain) or palpitations can be caused by problems with the heart. To understand the exact cause, your doctor may suggest one or more of the tests described in this factsheet. Similar tests may be done for people who are taken to hospital in an emergency, such as a heart attack.
Understanding the heartThe heart is a muscular pump made up of four chambers - two atria and two ventricles, connected through valves.
A heartbeat starts with an electrical impulse in the right atrium, at the top of the heart. This impulse is conducted across the atria, causing them to contract and pump blood into the ventricles through a set of heart valves (mitral and tricuspid valves). Once the blood is in the ventricles these valves close. The electrical impulse is carried down the centre of the heart and into the ventricles. This in turn causes them to contract, pumping blood around the body through a second set of valves (aortic and pulmonary valves). Coronary arteries bring oxygen-rich blood to the heart, which it needs to keep pumping. A common heart condition is coronary heart disease (CHD), in which fatty deposits gradually block the coronary arteries. This can result in angina or a heart attack (myocardial infarction, or MI). Other factsheets in the ABC of health series explain more about the heart and circulation. Please see Further information, at the end of this factsheet. This factsheet covers some of the tests that check if the heart is working normally. It also covers tests that assess the progress of CHD, or the effects of a heart attack.
Resting electrocardiogram (ECG)This test records the rhythm and electrical activity of the heart while a person is at rest. Some GPs have an ECG machine in the surgery. You will be asked to lie down, before a number of wires (usually 10) from the machine are attached to your chest using sticky patches. A trace (outline) of the heartbeat is shown on a screen, or printed onto a paper strip. The test, which only takes a few minutes at most, can show:
The results of this test may be normal even if someone has severe CHD. If heart disease is suspected, other tests may still be needed. 24 hour ECG recordingThis test means wearing a small electronic recorder for 24 hours or sometimes longer, connected to the chest by leads. The device, which is about the size of a deck of cards, can be attached to your belt or kept in your pocket through that time. You'll also be given a timesheet and asked to keep a log of any cardiovascular symptoms, such as palpitations, dizziness or pain, that you experience throughout the test. The recordings are then analysed in the cardiology department. The test can reveal intermittent arrhythmias and detect evidence of CHD. Implantable loop recorderA small electronic box, about the size of a packet of chewing gum, is inserted beneath the skin of the chest (under local anaesthetic) and left in place for up to 14 months. It monitors heart rhythms 24 hours a day and is good for detecting arrhythmias missed during a 24-hour ECG. This can be useful in determining the cause of fainting, dizziness or palpitations. Exercise ECG testingThis test is usually done in a hospital setting as specialised equipment is needed. The person walks or runs on a treadmill or cycles on an exercise bike, with leads attached as they are for a resting ECG. The test may be made gradually more difficult, by increasing the gradient on a treadmill for example. As angina symptoms often occur on exercise it is useful to see if there are changes in the ECG while the person is exercising. It can:
Radionuclide testIn this test, you're given a small, harmless injection of radioactive material, which is taken up by the heart muscle. The amount taken up depends on how efficiently blood travels to the heart muscle. The test may be done on a treadmill or exercise bike. A large camera directed at the heart picks up rays sent out by the radioactive material. Its pictures show if any areas of the heart are not getting enough blood. The test can help to diagnose coronary heart disease. It can also help doctors to decide if coronary bypass grafting (when a section of vein from the leg is transplanted to bypass a blockage in an artery) or balloon angioplasty might be successful. EchocardiogramIn this test, harmless ultrasound waves (high-frequency sound) are sent through the chest with a probe moved across the skin. The echoes that bounce off the heart are used to create a moving image of the heart on a screen. The test can sometimes take up to an hour. The echocardiogram scan can give accurate information about the structure and the function of the heart muscle and valves and the pumping function of the heart. An echocardiogram is often used for detecting complications following a heart attack. These include bulges due to muscle weakness (aneurysms) in the left ventricle (which sends oxygen-rich blood to the rest of the body) or damage to one of the heart valves. The technique is also used to help diagnose heart failure (when the heart is not pumping as well as it should). For a transoesophageal echocardiogram (TOE), you are sedated before a small ultrasound probe is inserted into the oesophagus (gullet). Images can then be taken without the ribcage and lungs interfering. The procedure is often used to get a clearer look at the heart valves. You shouldn't eat or drink for a few hours before having a TOE. Although you won't have to stay in hospital overnight, it isn't safe to drive for at least 24 hours after the procedure because of the effect of the sedative. AngiographyThis X-ray based procedure is a way of looking at the coronary arteries. While you lie down, a thin, hollow tube (catheter) is inserted into the femoral artery in the groin and threaded up to the coronary arteries. A dye is then injected through the catheter, which makes any narrowing or blockages in the coronary arteries clearly visible in an X-ray. The test is uncomfortable and there is some risk of complications, such as a reaction to the dye. You may need to recover overnight in hospital. Sometimes, blockages are treated at the same time with balloon angioplasty (also known as percutaneous transluminal coronary angioplasty or PTCA). A small balloon is inflated inside the artery to open it up. An expandable wire mesh tube, called a stent can be placed to keep the artery open. These sometimes release drugs which help the arteries stay open. Cardiac enzyme testingDuring a heart attack, damaged heart muscle releases enzymes - proteins that speed up chemical reactions in the body - into the blood. Levels of the enzymes can be measured by blood tests. The larger the rise in enzymes, the more heart muscle damage has been done. Creatine kinase (CK), troponin T and troponin I are the markers most commonly tested for. MRI (magnetic resonance imaging)MRI scanners use powerful magnets to make a detailed picture of tissues and organs inside the body. They don't expose you to radiation like X-rays do. It can take a while - about an hour - to create a good-quality image. It can be useful for identifying cardiomyopathy - a condition when the heart muscle is diseased - and narrowed coronary arteries. For more information about MRI, see the separate BUPA health factsheet MRI scan. Electrophysiological testingThis is used to find out which part of the heart is causing an arrhythmia. A catheter is threaded to the heart, via the groin or neck, and delivers tiny electric shocks, provoking the abnormal rhythm. Once located, the abnormal area can be destroyed with an electric shock, chemical solution or various drugs, stopping the abnormal rhythm. PET scanningFor a positron emission tomography (PET) scan, you're given an injection of a small amount of low-dose radioactive material, before lying under a scanning device. Using the scanner, doctors are able to examine blood flow and see your heart working. PET scans are useful for deciding whether a person needs balloon angioplasty or a coronary artery bypass graft (CABG) in complicated cases. Electron beam computed tomography (EBCT)Electron beam computerised tomography uses X-rays to create high quality images of the heart and coronary arteries, without the need for an invasive procedure. It can measure the extent of coronary artery disease, but it is not routinely used as a diagnostic test. It is more accurate at ruling out CHD than confirming it. Further informationSee the BUPA health factsheets:
Sources
Reviewed by Dr James Quekett, Bsc.MB Ch.B MRCGP DRCOG DFFP, partner/principal general practitioner at Rowcroft Medical Centre. Published by BUPA's health information team, healthinfo@bupa.com, March 2007.
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