If a heart attack is suspected, you should be admitted to hospital immediately. You will usually be admitted to an acute cardiac care unit (ACCU), or directly to the cardiac catheterisation unit, to confirm the diagnosis and begin treatment.

Electrocardiography

An electrocardiogram (ECG) is an important test in suspected heart attacks. It should be carried out within 10 minutes of being admitted to hospital.

An ECG measures the electrical activity of your heart. Every time your heart beats, it produces tiny electrical signals. An ECG machine records these signals onto paper, allowing your doctor to see how well your heart is functioning.

An ECG is painless and takes about five minutes to perform. During the test, electrodes (flat metal discs) are attached to your arms, legs and chest. Wires from the electrodes are connected to the ECG machine, which records the electrical impulses.

An ECG is so important because:

• it helps confirm the diagnosis of a heart attack
• it helps determine what type of heart attack you have had, which will help determine the most effective treatment

Types of heart attack

Heart attacks can be classified by a measurement known as the ST segment. The ST segment is an electrical measurement recorded by an ECG. It corresponds to the level of damage inflicted on the heart.

The higher the ST segment, the greater the likely damage.

Acute coronary syndrome

A heart attack is a form of acute coronary syndrome (ACS), where there is a significant blockage in the coronary arteries.

There are three main types of ACS:

• ST segment elevation myocardial infarction (STEMI)
• non-ST segment elevation myocardial infarction (NSTEMI)
• unstable angina

The three types are described in more detail below.

ST segment elevation myocardial infarction (STEMI)

A STEMI is the most serious type of heart attack, where there is a long interruption to the blood supply. This is caused by a total blockage of the coronary artery, which can cause extensive damage to a large area of the heart.

A STEMI is what most people think of when they hear the term "heart attack".

Non-ST segment elevation myocardial infarction (NSTEMI)

An NSTEMI can be less serious than a STEMI. This is because the supply of blood to the heart is only partially, rather than completely, blocked.

As a result, a smaller section of the heart is damaged. However, NSTEMI is still regarded as a serious medical emergency.

Unstable angina

Unstable angina is the least serious type of ACS although, like NSTEMI, it is still regarded as a medical emergency.

In unstable angina, the blood supply to the heart is still seriously restricted, but there is no permanent damage, so the heart muscle is preserved.

Other tests

A number of other tests can be used to assess the state of your heart and check for related complications. However, because heart attacks are medical emergencies, some tests are usually only carried out once your initial treatment has begun and your condition has been stabilised.

Blood tests

Damage to your heart from a heart attack causes certain proteins to slowly leak into your blood. Enzymes are special proteins that help regulate chemical reactions that take place in your body.

If you have had a suspected heart attack, a sample of your blood will be taken so it can be tested for these heart proteins (known as cardiac markers). Your protein levels will be measured through a series of blood samples taken over the course of a few days.

This will allow damage to your heart to be assessed, and also help determine how well you are responding to treatment.

Read more information about blood tests.

Chest X-ray

A chest X-ray can be useful if diagnosis of a heart attack is uncertain and there are other possible causes of your symptoms, such as a pocket of air trapped between the layers of your lungs (pneumothorax).

A chest X-ray can also be used to check whether complications have arisen from the heart attack, such as a build-up of fluid inside your lungs (pulmonary oedema).

Echocardiogram

An echocardiogram is a type of ultrasound scan that uses sound waves to build up a picture of the inside of your heart.

This can be useful to identify exactly which areas of the heart have been damaged and how this damage has affected your heart’s function.

Coronary angiography

Coronary angiography can help determine whether a blockage or narrowing has occurred in the coronary arteries and, if so, to locate the exact location of the blockage or narrowing.

The test involves inserting a thin tube, known as a catheter, into one of the blood vessels in your groin or arm. The catheter is guided into your coronary arteries using X-rays.

A special fluid, known as a contrast agent, is pumped through the catheter. This fluid shows up on X-rays, and studying how it flows around and through your heart can help locate the site of any blockage or narrowing.

A coronary angiogram is often performed just before surgery, as the results can help guide the efforts of the surgeon. Read our page on treating a heart attack for more information.

Blood

Blood supplies oxygen to the body and removes carbon dioxide. It is pumped around the body by the heart.

ECG

An ECG (electrocardiogram) is a test that measures electrical activity in the heart and is used to identify heart problems. 

Enzyme

Enzymes are proteins that speed up and control chemical reactions, such as digestion, in the body.

Heart

The heart is a muscular organ that pumps blood around the body.

Heart attack

A heart attack happens when there is a blockage in one of the arteries in the heart.

Inflammation

Inflammation is the body's response to infection, irritation or injury, which causes redness, swelling, pain and sometimes a feeling of heat in the affected area.

Kidney

Kidneys are a pair of bean-shaped organs located at the back of the abdomen, which remove waste and extra fluid from the blood and pass them out of the body as urine.

Liver

The liver is the largest organ in the body. Its main jobs are to secrete bile (to help digestion), detoxify the blood and change food into energy.