The electrocardiogram (ECG) is the oldest test in cardiology and has been around for over 100 years. It records the electrical activity of the heart for 12 seconds. It is performed by placing 10 electrodes at specific points across the chest and on the arms and legs. The test takes only a few minutes and is painless. The ECG is very useful and is performed on nearly all patients who present with a possible heart problem. It can diagnose heart rhythm problems (such as if someone is in atrial fibrillation) and also if someone has had a previous heart attack. It can also identify some diseases of the heart muscle, cardiomyopathy. Whilst the ECG is very useful it is often followed up with other tests to confirm the findings of the ECG and also to assess the heart in greater detail.

Although the standard 12 lead ECG is very useful this only records the electrical activity of the heart for a short period of time (12 seconds). With many heart rhythm disturbances these occur intermittently and the sensation of the heart beating (palpitations) is nearly always intermittent.

A 24 hour ECG records the electrical activity of the heart for 24 hours. Electrodes are placed across the chest and connected to a recording device that records and stores the electrical activity of the heart for 24 hours. This recording device and electrodes are then worn for 24 hours and patients are encouraged to perform normal daily activities as much as possible during the test. The electrical recoding of the heart is then downloaded after 24 hours (and after the electrodes and device have been removed from the patient) and then analysed in detail to look for heart rhythm problems and also assess the heart rhythm when palpitations occurred. The recording can also be done for longer than 24 hours although it is unusual to perform this test for more than 7 days.

An event recorder is another way of recording the electrical activity of the heart for longer periods of time. In this case the heart is not monitored continuously and recording occurs only for a short period of time when you have your symptoms. When symptoms occur then some devices which are carried are simply placed on the chest to record the electrical activity of the heart. Others are attached using electrodes (much as with the 24 hour tape) and the patient wears the device constantly and then presses a button to activate recording of the electrical activity of the heart. These devices are useful when symptoms do not occur very frequently.

Reveal devices allow for very long periods of monitoring (over 1 year). They are small devices (around the size of half of an index finger) which are implanted under the skin in the chest. They constantly monitor the heart and store any electrical activity of the heart which appears to be abnormal. The electrical data which is stored can be easily accessed by placing a receiver over the reveal device on the chest wall and downloading the data (this is a painless procedure). Although extremely useful when symptoms are rare to implant this device does require a small procedure under local anaesthetic and also a small (1-2cm) scar will form from the incision made in the skin through which the device is inserted under the skin.

A transthoracic echocardiogram (often just called an echocardiogram or echo for short) is a very commonly used test in cardiology. This uses an ultrasound probe placed on the chest to visualise the heart chambers and valves. A gel is often used on the surface of the chest to improve the contact of the ultrasound probe with the skin and improve the quality of the images. Moving images of the heart are taken and stored. Various different types of images can be taken to assess the heart in more detail. Doppler is often used to measure flow and pressure (which is very useful when assessing the heart valves).

An echocardiogram can show how well the heart is pumping. It can also show if part of the heart muscle has become thickened (such as in high blood pressure or certain diseases of the heart muscle) or thinned (such as after a heart attack). Leakiness or narrowing of the heart valves and indeed any abnormality of heart valves can be assessed in great detail using an echocardiogram.

For some types of studies a contrast agent is injected into a vein in the arm. This makes it easier to see the chambers of the heart and how well they are contracting. It also makes it easier to see if there are any abnormal structures within the heart such as a clot. Contrast can also be very useful to assess if there is a hole in the heart. When a hole in the heart is large then it can often easily be seen but when it is small often is can only be identified by seeing the abnormal flow of contrast between the heart chambers.

A stress echocardiogram is where the contraction of the heart is studied during rest and after stress (in other words speeding the heart up). If there is a significant narrowing of a heart artery when the heart exercises the part of the heart muscle supplied by the narrowed artery will not receive enough oxygen and nutrients. It will then begin to contract or pump abnormally. This can then be seen on an echocardiogram performed during this stress. To exercise or stress the heart drugs may be used which are given as an infusion into the veins or exercise can be performed and then stopped for a short period whilst the ultrasound images are taken.

This is very similar to a transthoracic echocardiogram in that it uses an ultrasound probe to visualise the heart chambers and valves. The difference is that for TOE the probe is inserted down the oesophagus (gullet) until the heart can be seen. This test is performed under sedation and a spray to numb the back of the throat (anaesthetic spray) is often used. It is particularly good for looking for clots in certain chambers of the heart and also for assessing the heart valves in detail.

Magnetic resonance imaging (MRI) has revolutionised many areas of medicine but it is only recently that MRI has been able to assess the heart. This is because the heart contracts with every heart beat and also moves within the chest during breathing which makes it harder to image with MRI than other organs in the body. Cardiac MRI (CMR) uses powerful magnets and radiowaves to image the heart. It does not use what is called ionising radiation (which includes X-Rays, nuclear imaging tests and CT scanning). Since there are no known long term hazards from CMR this makes it a very useful test. Also the resolution of the images from CMR is high which means it can provide extremely detailed information about the heart. Most people are able to have a CMR. As it requires lying down inside a tube for 30 minutes some people who are claustrophobic may not be able to tolerate the scan although modern MRI scanners have a larger hole inside (these are called wide bore scanners). Since powerful magnets are used it is not possible to scan patients who have certain metallic devices. Patients with certain types of metal clips in the brain cannot have a scan. Most patients with pacemakers cannot have a CMR Scan (although this is now changing and this is possible for some patients). However, many metal implants are perfectly safe. These include all heart stents and valves and all metal knee and hip replacements. In most cases a contrast agent will be given in the middle of the scan which will be injected into a vein.

CMR has many uses and the exact scan that is performed varies depending on your symptoms and the results of your other tests. CMR is the best test for looking at how well the heart chambers pump. It can also look for scarring in the heart and it is the only test that can look directly for scarring. The commonest cause of scarring in the heart is a heart attack but other diseases of the heart muscle (cardiomyopathy) cause certain patterns of heart scarring which CMR can detect. It can also look at the heart valves although an echocardiogram would usually be performed first). It can look for swelling of the heart (called oedema) which can be useful if there is inflammation of the heart (such as in myocarditis).

One very common use for CMR is to assess if the heart arteries are narrowed or blocked. This is a stress CMR. Medication is given through a vein to exercise or stress the heart for 3-4 minutes. After this contrast or dye in injected and images of how the dye enters into the heart muscle are taken (this is called perfusion of the heart). An abnormal CMR perfusion scan can be used to assess if the heart arteries are narrow and to try to determine which heart arteries are affected.

This is a relatively new test to look directly at the heart arteries. Although CT scanning has been available for many years the scanners were not able to image the heart and the heart arteries properly as the heart contracts with each heartbeat. Modern CT scanners are extremely fast and therefore able to achieve this. CT scanning involves lying in a tube but this tube is not as long as for a cardiac MRI scan.

With a heart CT scan there are two parts to the assessment. The first is a non contrast scan (in other words no dye is injected) to look for and measure any calcium in the heart arteries (called a CT coronary calcium score). This is important to assess because high calcium scores indicate that it is more likely you will suffer problems with the heart arteries (such as angina or a heart attack) in the future. The second part of the scan involes and injection of dye or contrast which then allows the heart arteries to be seen in more detail and to look for any narrowing or blockage of any of the heart arteries.

Although this test does involve ionising radiation (like an X-Ray) the amount of radiation has been reducing steadily as the CT scanners have become faster and more sophisticated. Modern CT scanners use only the same amount of radiation as for a coronary angiogram and often use less. With a CT coronary angiogram test only the heart arteries are usually assessed as to assess the pumping function of the heart or the valves of the heart there are other tests which are used (such as echocardiography or cardiac MRI).

A coronary angiogram (often referred to as an angiogram) is an invasive test to look for narrowings or blockages to the heart arteries. This test is performed with patients lying flat on a movable table. A small tube called a catheter is inserted under local anaesthetic into the artery in either the wrist or the groin. This tube is then moved using X-Ray guidance up and around the arteries of the body into the heart arteries. Images of the heart arteries are then taken using X-Rays and the injection of a dye (also called contrast) through the catheter into the heart arteries. There are different types of catheters which are used to look at each heart artery in turn.

If the heart arteries are significantly narrowed or blocked then they can be treated by stretching them open with a balloon and inserting a stent to keep the artery open. This is called percutaneous coronary intervention (PCI) or sometimes called angioplasty. Once an angiogram has identified the narrowed portion of the artery a very fine wire is passed up through the catheter in the wrist or groin into the heart artery. This wire is then carefully passed across the narrowing or stenosis in the artery. A balloon is then guided over this wire and inflated at the location of the narrowing to stretch the heart artery open. Finally a metal scaffold called a stent (which is attached to a balloon) is passed via the fine guidewire to narrowed part of the heart artery and the balloon on which the stent sits is inflated to press the stent firmly into the wall of the heart artery and thereby keep the heart artery open. Originally stents were made of metal only (called bare metal stents). More recent stents have special drug coatings on them (drug eluting stents). These coated stents reduce the risk of the narrowing of the heart artery recurring (called restenosis).

Sometimes an artery can be partially narrowed and it is difficult to work out from just the angiogram pictures whether the narrowing requires treatment with a stent. There are 2 tests that can assess part of the heart arteries in more detail. The first is a special ultrasound probe that can be passed over a fine guidewire across the narrowing in the heart arteries to take ultrasound images of the artery to see the amount of narrowing in more detail. This is called IVUS (intravascular ultrasound). The second uses a special fine wire to assess the flow across the narrowing and how much the flow is reduced. This special wire is carefully passed across the narrowing in the heart artery. The heart arteries are then fully relaxed using drugs which are given through the veins for 1-2 minutes. The drop in flow across the narrowing can then be assessed in more detail to make a decision whether it requires treatment. This test is called a pressure wire (also called FFR, fractional flow reserve).

The rate at which your heart beats is normally automatically controlled by the heart itself. This can vary quite considerably during a 24 hour period. Our hearts beat more slowly at night and faster when we exercise. Electrical impulses lead to the heart beating. Where there is a disease of the electrical circuits which control the heart then the heart may beat more slowly. This is known as heart block. With some types of heart block a pacemaker is required to speed up the heart beat.

A pacemaker consists of two components; the leads and the generator box. A pacemaker is often inserted with sedation. Patients lie flat on a movable table. Most pacemakers are inserted on the front of the chest just below the collar bone on the left side. This area is numbed first with local anaesthetic. The veins under the collar bone are then identified. Through one of these the leads of the pacemaker are inserted and then passed around to the correct chambers in the heart under X-Ray guidance. A small pocket is then made under the skin and a small incision is made. The pacemaker generator is then inserted into this pocket, attached to the leads and then the incision in the chest is the sutured back together. The generator contains both the battery for the pacemaker and also the monitoring equipment to assess the electrical acticity of the heart and make sure that the heart is paced (or electrically activated to beat) approrpriately.

After the pacemaker has been inserted it needs to be checked to ensure that it works properly and problems with the leads and the generator have not occurred. The remaining battery life also needs to be noted. Most modern pacemakers have a battery life of several years. To do this a receiving device is placed over the pacemaker whilst lying down and the pacemaker and leads can be assessed. Also if the way in which the pacemaker is working needs to be adjusted this can be done at the same time.

If the pacemaker battery begins to run out then the generator box will need changing. With local anaesthetic and whilst lying down the old generator is removed by making a small cut into the skin and taking it out and a new generator inserted.

There are now special types of pacemakers that can improve the pumping of the heart if it is not pumping properly (heart failure). These pacemakers have more leads but the way in which they are implanted and checked is similar to a normal pacemaker. These devices are called biventricular pacemakers.

For some conditions it is now possible to implant a device that will deliver an electric shock to the heart if it is at risk of developing a heart rhythm for which the best treatment is a rapidly delivered shock to the heart to restore a normal heart rhythm. These devices are again inserted in a similar way to a normal pacemaker and they can be checked in a similar way to a pacemaker although sometimes more specialist checking that the device is working correctly is required.

Although an ECG and monitoring with a 24 hour tape can provide a lot of information about the electrical activity of the heart sometimes more information is needed. An electrophysiology study (called an EP study) provides detailed information about your heart's electrical activity. It can be useful to assess certain heart rhythm problems, particularly if treatment with an ablation is being considered. After lying down on a movable table local anaesthetic is inserted into your groin. A flexible tube (called a catheter) is carefully passed through the veins in the leg around and into the chambers of the heart under X-Ray guidance. At the end of this catheter there are small electrodes which are placed carefully on the inside surface of the heart chamber to record the electrical activity of the heart.

For some heart rhythm problems an ablation can be performed to treat the abnormal heart rhythm and prevent it recurring. The commonest heart rhythm problem that can be treated is atrial fibrillation (AF). Once the electrical activity from the heart chambers has been assessed with an EP study a catheter called an ablation catheter is passed though the vein in the leg into the heart chambers. Certain heart rhythm problems are due to abnormal electrical impulses developing at certain sites within the heart. These areas where the abnormal electrical impulses develop are then treated by through the ablation catheter applying radiofrequency impulses to a small area of the heart and thereby destroying or ablating the source of the abnormal heart rhythm. The exact procedure and the amount of ablation required varies according to the heart rhythm problem and this is discussed before the procedure.

A chest x-ray is one of the oldest tests used in cardiology. An x-ray image of the chest is taken with the patient standing in front of an x-ray plate. A chest x-ray can show if the heart is enlarged and also show if there is fluid in the lungs which can occur in heart failure. Although useful an abnormality found on a chest x-ray is usually confirmed with additional investigations.

This test was commonly used to assess for narrowings or blockages to the heart arteries. A small amount of radioactive dye or contrast is injected into the bloodstream and a series of images taken which show how this dye enters the heart muscle (this is called the perfusion of the heart) using a special camera (gamma camera). This test is performed twice, once at rest and once during stress when the heart is exercising. For the stress images to exercise the heart drugs are often injected into a vein in the arm to speed up the heart. Another way is for the patient to perform exercise such as on a treadmill.

Although still occasionally used this test is now used less than previously. This is because it involves ionising radiation and other tests such as cardiac MRI and stress echo can give similar information without the need for ionising radiation. There is also evidence that it is less accurate than other tests such as cardiac MRI.

This is an extension of a normal ECG. As with an ECG, electrodes are attached to your chest. An electrical recording of the heart is taken at rest and then at regular intervals whilst the patient performs increasing amounts of exercise. The blood pressure is also monitored during this test. The most common form of exercise is a treadmill but an exercise bike can also be used. The ECG traces can then be analysed after the test. Certain changes can indicate narrowings of the heart arteries. However, this test is not very accurate and can give misleading results (called a low sensitivity and specificity). It is therefore used less often than previously and other tests such as cardiac MRI and stress echo are more often used.

This uses ultrasound waves to image the neck vessels. An ultrasound probe is placed on the neck to visualise the neck arteries and veins. A gel is often used on the surface of the neck to improve the contact of the ultrasound probe with the skin and improve the quality of the images. Images of the neck vessels are taken and stored. Various different types of images can be taken to assess the various vessels in more detail. Doppler is often used to measure flow and pressure across the vessels which can be useful to assess the amount of narrowing of a blood vessel. This test is sometimes performed before heart surgery to make sure that the neck arteries are not diseased or narrowed which increases the risk of a stroke during heart bypass surgery. There is also some evidence that even very minor narrowings of the head and neck arteries indicate an increased risk of certain heart problems in the future (such as angina or a heart attack).