Heart attack

Diagnosing a heart attack

Most heart attacks are diagnosed from the results of an electrocardiogram [ECG] and a blood test, which can confirm whether or not a heart attack is occurring and if so, how it is affecting the heart. An ECG is often done in the ambulance by paramedics to make a preliminary diagnosis of a heart attack. While the final diagnosis rests in the hands of doctors, that preliminary diagnosis is important because it allows paramedics to begin treatment immediately - often while still in the patient's home (see ‘Pre-hospital care in the ambulance for a heart attack’). An ECG can also be done in a GP’s surgery.

The classic sign of a heart attack on the ECG is known as ST elevation. This is the electrical signal produced by a damaged segment of the heart muscle, and heart attacks which display this are known as "STEMI" - ST- elevation myocardial infarction. If a heart attack occurs without this ECG signal, it is known as NSTEMI (the N standing for non-). Such heart attacks are usually diagnosed on the basis of blood tests such as troponin-T and other enzymes released by damaged heart cells. These can take a few hours to show up in the blood so it is common practice to admit patients with possible heart attacks for a period of hours to get a second blood test. These blood tests are not used as a way to decide on immediate treatment but can be used to assess the level of damage to your heart and how well you are responding to treatment. Both STEMI and NSTEMI heart attacks are also referred to as "Acute Coronary Syndromes" (ACS), together with the separate condition of unstable angina, which we do not cover here.
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One woman described the series of tests she had done, in the ambulance, and over the next few days while she was in hospital to assess the amount of damage caused by the heart attack and a few months later to establish whether she would need further treatment for narrowing of her coronary arteries.

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Occasionally, making a diagnosis is not straightforward and it can take some time before a heart attack is confirmed. One woman said that a series of ECGs carried out in hospital at first showed no changes - to confirm she was having a heart attack, even though she was getting attacks of chest pain.

The timing and type of blood tests taken are important in diagnosis. A man in his thirties explained that when he had a heart attack after bypass surgery, the ECG showed no significant changes in his heart.

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Another man in his forties said that the x-ray and the blood tests at first showed no abnormalities and he was sent home, but the stress test (treadmill ECG) he had two days later showed he had had a heart attack.

Other tests such as a chest x-ray, an echocardiogram, other heart scans or a coronary angiogram may be used to assess the severity of the heart attack and to help decide on the best form of treatment. Whether these further tests are done at once or later will depend both on what is immediately available and on the patient's condition. See 'The general ward and discharge home after a heart attack' for more on the exercise ECG (also known as the 'treadmill' test).

Most people said having an echocardiogram, which is an ultrasound picture of the heart shown on a TV monitor, was very straightforward. One man, who after a week in hospital was still unstable, was sent for an angiogram, which showed that further treatment was necessary.

A coronary angiogram is a test that shows which, if any, arteries supplying the heart are narrowed. Usually, it is a day case procedure done under local anaesthetic. Some people we interviewed in 2006 had to wait eight or nine months to have a coronary angiogram, others waited one or two months and some had the test a few days after their heart attack while they were still in hospital recovering.

Those who had waited a long time said they were anxious to have the tests done soon, so that if treatment was necessary it could be done as soon as possible. Waiting times vary around the country. How long you wait depends how urgently your doctor considers you need the coronary angiogram. A few people decided to pay to have the coronary angiogram done privately. One man had asked to be put on the cancellation waiting list in the hope of getting it done sooner.

Some had been anxious before or during the test, but said it was nothing to be frightened of and it wasn't as bad as they had expected. One man said that it helped that his doctor explained to him what was happening all the way through the procedure.

Some found it interesting to watch the procedure on the television screen. People are given a local anaesthetic and most said they had no pain. The only thing they felt was a warm sensation as the “dye” (which shows up on the x-ray pictures) flushes round their body. 


Last reviewed June 2017.

Last updated June 2017.


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