London Heart

Cardiac Diagnostic Tests

Electrocardiogram (ECG)

An ECG gives an overview of the function of the heart. It involves placing 12 stickers on your arms, legs and chest and provides information about various aspects of the heart structure and function.


An echocardiogram or echo for short is an ultrasound scan of the heart. It can give detailed pictures of the moving heart and provides lots of valuable information. To conduct the test, a small ultrasound probe is placed in different positions on your chest by an echo technician or cardiologist. The scan tells us how your heart is beating, whether the heart has any structural abnormalities and provides information about the heart valves.

Transoesophageal Echocardiogram (TOE)

This test involves passing an ultrasound probe through your mouth and down your food pipe (oesophagus). As the ultrasound probe sits closer to your heart, the images obtained are of better quality than a normal echocardiogram. A TOE is usually performed with a local anaesthetic spray into the mouth and sedation to make you comfortable. It is usually performed to provided detailed information about the heart structure and function including the heart valves. A TOE can also provide information about whether there are any blood clots in the heart which may put you at risk of stroke.

Stress Echocardiogram

This is a special type of echocardiogram. This involves using an ultrasound machine to take detailed pictures of the heart from a probe on the chest. A normal echo takes pictures of the heart when you’re resting. Sometimes, it can be helpful to get pictures of the heart whilst it is under stress.

This can be done in two ways:

  1.  Exercise – via walking on a treadmill or exercise bike
  2. Drug – If you can’t use a treadmill or exercise bike, drugs can be used to make the heart beat faster and harder.

There are some conditions that are only apparent when the heart is under stress and some are magnified by the stress. Therefore, sometimes a stress echo may be able to give answers and information that a normal echo can’t. The main reson for performing a stress echo is to see if there is suffient blood reaching your heart muscle when you exercise or exert yourself.

Ambulatory ECG Monitor (holter)

This is a test which analyses your heart rhythm. A holter monitor is often used to investigate patients with palpitations of blackouts or who have a particularly slow or fast heart rate.

For this test, you will be connected to a heart rhythm monitor (ECG monitor) which you will wear for a prolonged period of time, usually 24 hours but up to 7 days. This is done by connecting leads that are stuck onto your chest and connected to a small box which you will carry around. The monitor takes only a few minutes to fit and you carry on with your activities as you would normally. The monitor will continuously monitor your heart rhythm during this time. You will also be given a button, which you can press if you feel any symptoms, i.e. shortness of breath, palpitations or dizziness. Your Cardiologist can then see if your symptoms correlate to any abnormal heart rhythms. After the set period of time, the device will be removed and the data can be analysed. Newer devices are in the form of a patch which sticks on your chest like a plaster. These are easier to wear with less restrictions.

Implantable Loop recorder

In patients with infrequent symptoms of palpitations dizziness or blackouts an ECG monitor may not reveal any abnormality. In these cases a small device, approximately the size of three matchsticks, can be implanted easily under the skin to monitor the heart rhythm continuously for up to three years. These devices are then used to correlate your symptoms with your heart rhythm recording to see if there is an abnormality. The devices have evolved considerably and can now be implanted in an outpatient clinic in a matter of minutes using local anaesthetic. The incision is tiny and in most cases stitches aren’t required. In addition the devices have wireless functionality meaning that your heart rhythm can be analysed without you needing to come into hospital.

Exercise treadmill test

As the name implies this test involves you walking on a treadmill connected to an ECG. The intensity of exercise increases progressively. The test provides information about your heart function during exercise. Your ECG and blood pressure is monitored closely and it is also useful to assess whether you are having any symptoms of chest pain, which may be indicative of narrowings in the coronary arteries.

Cardiac MRI scan

A Cardiac MRI scan is perhaps, the scan that gives the most detailed pictures of the heart. It involves a magnetic field and radiowaves, which feed into a computer. This can then provide very detailed pictures of the heart. It can make assessments on how well the heart is pumping and provides information about any structural problems with the heart. Using a special drug it can also be used to provide information about potential narrowings in the coronary arteries. As the scanner incorporates a large magnet, it is not suitable for everyone. If you have metal joint replacements and certain types of pacemaker, you may not be suitable to have an MRI scan.


This is an invasive test to assess the coronary arteries which provide the blood supply to the heart. Any blockages in the blood supply can lead to angina and heart attacks. An angiogram involves passing small tubes through the artery in the wrist or groin. These are then advanced up to the heart where small amounts of contrast or dye are injected into the coronary arteries. Using an x-ray machine, pictures can then be taken of the coronary arteries. These pictures can then show if there are any narrowings or blockages in the arteries which could be interrupting the blood supply and preventing blood getting to the heart and causing symptoms.

Cardiac CT scan

A Computer Tomography scan of the heart (a Cardiac CT) is a scan that is being more and more commonly used to look at the blood supply to the heart (the arteries). In previous years, in order to get pictures of the blood supply of the heart, you would have needed to have an angiogram, which is an invasive test. This is non-invasive (i.e. no need for needles or wires inside the body). To do this, dye is injected into the blood stream via a small tube in the arm. You will then pass through the scanner and pictures of the coronary arteries can be obtained. The scan can show if there are any narrowings or blockages in the arteries which may be causing symptoms (i.e. chest pain) and which may require intervention such as stents or surgery. The scan is very safe and in only a small number of cases image quality may be limited by artefact.