Diagnostic tests

CAT scans provide high resolution CAT scans provide high resolution images

Tests to establish whether people are at risk of, or have suffered, heart disease or stroke can involve chemicals being injected into the body - invasive - or readings taken externally only - non-invasive.

Non-invasive

Electrocardiography

An electrocardiogram (ECG) measures the rhythm and electrical activity of the heart.

Small metal patches, called electrodes and set in sticky plaster, are put on the arms, legs and chest and connected by wires to a recording machine.

The test can detect abnormalities of heart rhythm and can tell whether the patient has had a heart attack in the past.

The test has limitations - abnormal readings can have an innocent explanation and some patients with serious heart problems can have a normal ECG.

Exercise ECG, otherwise known as exercise stress testing, is an ECG taken while exercising on a treadmill or stationary bicycle.

It is often more accurate than a resting ECG and is used to test whether there is a lack of blood supply through the arteries that go to the heart.

The exercise is made increasingly difficult and blood pressure and breathing are monitored at the same time.

Holter monitoring, also known as 24-hour ECG, involves electrocardiogram recordings taken over 24 hours and can help diagnose palpitations, which occur infrequently and can easily be missed in a short test.

The electrodes are placed on the chest and attached with wires to a small portable tape recorder which is worn on a belt around the waist.

The recorder - the Holter monitor - takes constant or intermittent readings.

Echocardiography

A pulse of high frequency, inaudible sound is transmitted through the skin by placing a recorder or probe on the chest wall.

The probe picks up the echoes reflected from various parts of the heart and displays them as an echocardiogram - a picture on a screen.

The recorded waves show the shape, texture and movement of the valves and the size and function of the heart muscle and chambers.

The test can take up to an hour and is painless.

It provides information about disease of the heart muscle for those who have suffered a heart attack or heart failure and to assess people with disease of the heart valves.

Doppler echocardiography measures the speed of the flow of blood in different parts of the heart.

Occasionally, echocardiography is carried out after the heart is put under stress either with exercise or a drug - stress echocardiography.

Magnetic Resonance Imaging (MRI scan)

Magnetic Resonance Imaging (MRI) produces detailed pictures of internal organs, including the heart and brain.

Patients lie in a short tunnel-like machine which contains a cylindrical magnet. Short bursts of magnetic fields and radio waves create images of parts of the body as required.

MRI can measure the flow of blood through some of the major arteries and can detect abnormal heart function in disorders such as cardiomyopathy (heart muscle disease), coronary heart disease, congenital heart defects and help define the location and extent of brain injury in stroke patients.

CT or CAT scan

High resolution images of the heart, brain and blood vessels are given by X-ray computed tomography (CT) or computerised axial tomographic (CAT) scans.

It is useful to evaluate disease of the aorta - the largest artery in the body and involves little potential risk to patients. In stroke patients, it gives valuable information about the location and extent of brain injury.

Blood tests - cardiac enzyme tests

Blood samples taken over a series of days can reveal the level of enzymes - proteins that help with chemical actions in the body and are released after a heart attack - in the blood.

Invasive

Coronary angiogram - cardiac catheterisation

Cardiac catheterisation is often used to assess whether people with angina require surgery.

The test gives vital information about blood pressure within the heart, how much oxygen is in the blood, the function of the pumping chambers and valves, and the exact severity and positioning of any narrowings in the coronary arteries.

A coronary angiogram - a picture of the coronary arteries - is produced.

The catheter - a long, flexible, plastic tube - is inserted into a vein or artery in the groin or the arm after a local anaesthetic is given.

The catheter is used to inject dye into the coronary arteries - this is called coronary angiography or coronary arteriograpy.

High speed X-ray "films" record the course of the liquid as it flows through the heart and arteries. Obstructions in the arteries can be identified by tracing the liquid's passage.

Cerebral arteriography is used to show the extent and location of hardening of the arteries in the brain in order to diagnose patients at risk of stroke.

The test takes between 20 minutes and an hour and is often done as day case, though some patients may have a short stay in hospital.

There is a very small risk - one in 700 - that the test will cause a heart attack.

Nuclear imaging

A very small and harmless quantity of radioactive substance, called an isotope, is injected into the blood, often while exercising.

Gamma rays emitted by the isotope - usually technetium or thallium - are picked up by a "camera" positioned close to the chest.

Technetium is used to test the size and pumping function of the heart chambers, taking pictures of the inside of the heart as it empties and fills.

Thallium is used to study the blood flow to the heart muscle, by taking pictures of the flow of blood to the muscular walls of the heart, and to provide more detailed information than the exercise ECG test.