Heart Attack

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I Had My Cardiac Enzymes Measured: A Case Study - What Does a Thallium Stress Test Involve?

What is a heart attack?
Most heart attacks are a result of coronary heart disease – the narrowing of the coronary arteries due to a gradual build-up of fatty material within their walls. This fatty material is called atheroma.

If the atheroma becomes unstable, a piece may break off and lead to a blood clot forming.

This clot can then block the coronary artery and the heart muscle is starved of blood and oxygen and could become permanently damaged. This is a heart attack and is sometimes known as acute coronary syndrome, myocardial infarction or coronary thrombosis.

During a heart attack, life-threatening heart rhythms may develop, which makes it a medical emergency.

If you think that you or anyone else is having a heart attack, you should call 999 immediately.

What is cardiac arrest?

Cardiac arrest happens when the heart stops pumping blood around the body because of a disturbance in the normal heart rhythm.

One of the causes of cardiac arrest is a heart attack. Other causes could include such things as electrocution, bleeding, choking or a drugs overdose.

What are the symptoms?

The symptoms of a heart attack vary from one person to another. They can range from a severe pain in the centre of the chest, to having mild chest discomfort that makes you feel generally unwell. Women may experience different symptoms to men.

The common symptoms of a heart attack include:

Central chest pain
The pain can spread to the arms, neck or jaw
Some people can feel feel sick or sweaty as well as having central chest pain
Some people can feel short of breath as well as having central chest pain.
The less common symptoms of a heart attack include:
A dull pain, ache or 'heavy' feeling in the chest
A mild discomfort in the chest that makes you feel generally unwell
The pain in the chest can spread to the back or stomach
Some people say that the chest pain feels like a bad episode of indigestion
Some people can feel a bit light-headed or dizzy as well as having chest pain.

How is a heart attack diagnosed?

If you are having or you suspect someone close to you is having a heart attack, call an ambulance.

When they arrive, the ambulance staff will assess your condition and start any treatment necessary before taking you to hospital. When you arrive, you will have a rapid assessment that includes:

An assessment of your symptoms and medical history
A physical examination including monitoring your heart rate and blood pressure
An electrocardiogram (ECG) to help diagnose your condition
Blood tests to help check for any damage to the heart muscle
While you are in hospital, other tests may be carried out to assess your heart and decide the best form of ongoing treatment.

What treatment could I expect to receive?

You could be given pain relief, oxygen and aspirin and a combination of medication, which you should keep taking after you go home.

Other treatment you are likely to have depends on the results of your tests and overall assessment of your condition. The most common types of treatment that are given to people with a heart attack are:

Thrombolysis: a treatment that helps dissolve the clot that is blocking the artery and helps to restore the blood supply to the heart. It involves injecting a drug in to the blood stream. Thrombolysis is sometimes called a clot buster.
Coronary angioplasty: a treatment to widen the artery.

Can I prevent coronary heart disease and heart attack?

Yes - even if you’ve had a heart attack there are several things that you can do to reduce the risk of future heart problems.

These include:

  • Stopping smoking
  • Controlling high blood pressure
  • Reducing blood cholesterol levels
  • Keeping physically active
  • Achieving and maintaining a healthy weight
  • If you have diabetes, controlling your blood glucose as much as possible.

I Had My Cardiac Enzymes Measured: A Case Study

Tony first became aware that something was wrong when he was watching TV at his home in Reading. “I had been feeling tired, but nothing unusual and my left arm was aching. I put it down to having pulled a muscle or something like that. As I watched a film with my wife, I started to feel much worse and my arm and chest began to feel very painful. My chest felt as though someone was sitting on it and I struggled to breathe,” says Tony. He was having the classic symptoms of a heart attack and his wife Helen acted quickly, called 999 and an ambulance arrived within minutes from the Royal Berkshire Hospital.

Arrival in Accident and Emergency

Helen travelled in the ambulance with Tony, keeping out of the way as the paramedics monitored his heart rate and gave him oxygen. They were at the hospital within 15 minutes and Tony was rushed to the cardiology emergency team. “By this time, I was feeling more panicky and realised that this could be it for me – it sounds melodramatic, but it did worry me that I was not going to make it,” remembers Tony.

So many monitors were hooked up to Tony that he now jokes that he was using up most of the electricity being produced by the national grid that night. With emergency treatment, his condition was stabilised quite quickly and then the doctors began to do some tests to see how bad the heart attack had been. “The cardiologist explained that some key cardiac enzymes were going to be measured. He said that this would help them to find out whether this had been a mild heart attack, as they suspected, or if it was more serious than it seemed,” says Tony.

Cardiac Enzymes Measured

Cardiac enzymes are molecules that are released as heart muscle dies, as it does when a blockage in a coronary artery cuts off the oxygen to heart muscle during a heart attack. The most reliable blood marker for heart muscle damage is a protein called troponin. This is a protein released only by heart muscle that has died; it is never normally present in blood but levels do rise after a heart attack. The higher the level of troponin in the blood within hours of symptoms of a heart attack, the more severe the cardiac episode has been.

“The test itself took some of my blood and it was sent off to the biochemistry labs. As well as troponin, other cardiac enzymes were also measured,” he recalls. Other markers of a heart attack include creatine kinase, lactate dehydrogenase, myoglobin and natriuretic peptides. Afterwards, Tony did some research on the internet and found out that the levels of troponin I and troponin T in the serum of people who have suffered chest pain can predict those most likely to die from their heart attack. “I didn't realise it was such a big deal at the time and Helen just thought it was a standard test. When the results came back that no troponin had been detected, we didn't realise the significance at first,” explains Tony.

No Troponin, Good Prognosis

Later, the cardiologist in charge of Tony's care took more time to explain the results and told the couple that the lack of troponin in Tony's blood was a very encouraging sign. It meant that his heart attack had been fairly mild and, because he had been rushed to hospital so quickly after his symptoms worsened, there was less damage to his heart muscle than their might have been with a delay. “That made me feel better, although it was still a long time before I was on my feet again. I feel I now have to care about my health much more and I have done a full cardiac rehabilitation program. With regular exercise and healthy eating, I hope to avoid ever having to repeat my experience,” says Tony.

What Does a Thallium Stress Test Involve?

If you have symptoms of heart disease, or a family history that suggests you may be at risk, it is important to have tests to monitor the way that your heart is working. The thallium stress test is one technique that is useful for visualising how well the blood flows to the heart muscle and through the heart when you are exerting yourself and when you are at rest. 

 It is called a stress test because it involves putting the heart under stress to see how it behaves. This is done either by exercise or by giving a drug to make the heart work harder.

Why is a Thallium Stress Test Done?

One of the main things that doctors look for during a thallium stress test is whether any of the coronary arteries are blocked, where any blockages are and how bad they are. It is also used to look at the heart of someone who has had a heart attack to assess the extent of muscle damage. After treatments such as coronary artery bypass surgery or balloon angioplasty, a thallium stress test can also show how successful the procedure has been, and if there are any outstanding issues with blood flow to the heart muscle. The test can also reveal why a patient is experiencing chest pain and how much exercise they can do without risking a heart attack.

What Happens During a Thallium Stress Test?

In the first stage of the test, you are asked to start exercising on a treadmill or exercise bike. You will be hooked up to a heart monitor and all your vital signs – heart rate, blood pressure and breathing rate – will be carefully checked. Once you have been exercising hard for a few minutes, the medical team will be able to see when your heart is working at its maximum level. It will now be under some stress. At this point, you will be given an injection containing radioactive thallium into one of your main veins.

As the radioactive thallium circulates through your body, you are asked to lie still under a gamma camera, which looks like a large scanner. As the thallium reaches your heart, the camera takes a series of pictures to build up a good view of how your heart muscle is getting new oxygenated blood. Any areas that are not properly perfused – they aren’t getting enough blood – will show up.

Over the next two hours or so, all you then have to do is lie still while the camera takes more pictures. The radioactive thallium keeps circulating through your body and, as your heart slows down as you recover from the exercise, this provides useful information about how your heart recovers from stress, and how blood flow to the muscle is maintained at rest.

What can a Thallium Stress Test Show?

Other tests can show how the blood flows through the coronary arteries at rest but this test uses exercise to stress the heart to give more realistic information. No-one lies still all day and doctors need to assess if someone with a normal looking heart is going to run into serious problems if they walk up a hill, for example. The test can show if a coronary artery is partially blocked, and may pose a danger of a future heart attack.

If you are having a thallium stress test after a heart attack, the test will show how much of your heart muscle has died. Dead areas of heart muscle do not take up radioactive thallium at all, so it is obvious how much of the heart has been damaged and how much may need to be bypassed in a coronary artery bypass operation.

What If I Can’t Do Exercise?

If you need a heart stress test but you are not well enough to ride an exercise bike or go on a treadmill, you will be given a drug such as adenosine. This will increase the amount of blood that flows to your heart, producing a similar effect to strenuous exercise. The results will show how your heart responds to stress, without putting you in danger from a sudden bout of exercise.

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