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Routes to a healthy heart:
Tests to help your recovery
ECG is an abbreviation of “electrocardiogram”. Information from these tests can be helpful for doctors monitoring your recovery from a heart attack, so it's possible that you will be asked to undergo an ECG at regular intervals after you leave hospital.
ECG tests: what is involved?
You may have already undergone several ECG examinations. If you have you will know that it is a simple and easy procedure that takes just a few minutes and should cause no pain. Electrodes are attached to your arms, legs and chest. These electrodes do not give you electric shocks. Instead, they record the electrical activity of your heart as it beats - this information is usually displayed on a paper strip and is recorded electronically for analysis.
When the test is complete the electrodes are removed, leaving no permanent marks on your skin. Having an ECG requires no injections or special preparation. It's a good idea not to eat a large meal just before an ECG.
Resting and exercise ECG tests
The description above applies to a “resting ECG”. There is another sort of ECG test, called an “exercise ECG”. The difference between these is that for the resting test you simply sit quietly or lie down while the test is in progress (usually not more than 5 minutes). In the exercise test you are asked to walk on a treadmill or pedal a cycling machine, usually for not more than 15 minutes. It's quite likely that you had an exercise ECG test in hospital just before you were sent home. When you have an exercise test your doctor or the person performing the test will explain in advance exactly what you need to do. Care will be taken to ensure that you work hard during the test but do not over-exert yourself: you should stop if you feel tired or breathless or develop chest pains.
If you are taking a beta-blocker you will probably be asked to stop using the drug for a few days before an exercise ECG test. This is because beta-blockers stop the heart rate rising during exercise and this can affect the results of the test.
What can the ECG tell doctors about your heart?
The results of an ECG – especially an exercise ECG – enable doctors to see how your heart performs when you are physically active. In particular, it can alert them if parts of your heart are not receiving as much oxygen as they need. This may be a sign that some of the coronary arteries in your heart are becoming blocked up again. Changes to your medication may be needed to prevent that happening or your physician may recommend that you have an angioplasty or a coronary revascularization operation ( PTCA) to widen the affected artery or arteries. Early action of this sort can reduce the risk of you having another full-scale heart attack.
Other tests
The ECG is a useful test but it is not 100% accurate – for example, some people who have coronary artery disease have normal ECGs during an exercise test whereas others, who have healthy hearts, have abnormal ECGs during exercise. Some people who have already had a heart attack have no sign of it on their ECG. For this reason, your doctors will probably want to do additional tests if they find unsatisfactory signs in your ECG. Other tests include angiography, echocardiography and radionuclide investigations. Angiography involves injecting a special dye into the bloodstream and then taking X-ray images of the heart. The dye is visible in these images, enabling doctors to identify places where the coronary arteries are becoming narrowed.
Echocardiography involves gathering information about your heart using reflected high-frequency sound waves. The information gathered in this way tells doctors quite a lot about how well your heart has recovered from your heart attack and about the adequacy of the blood supply to the heart, and can be used to help doctors decide if you would benefit from a coronary revascularization operation (PTCA or CABG). Echocardiography can also be used to monitor the success of such operations.
A standard echocardiography examination is a relatively simple procedure for you as a patient. You lie on a couch and the probe that emits the sound waves is placed on your chest: usually a clear lubricating gel is rubbed onto your chest to improve the contact with the probe. The technician then moves the probe around to get different views of the heart. This procedure is painless (apart from some pressure where the probe is pressed against your chest) but it can take time to get all the information doctors need, so the test may last 30 minutes or more.
There are several variations on the basic echocardiography test. Perhaps the best known of these are the exercise or 'stress' tests. For these you are asked to do a specific physical exercise (as with the ECG exercise test described earlier) or are given an injection of a special drug that makes your heart work harder. Using echocardiography to examine the way your heart responds to exertion can be useful for identifying any continuing problems with the supply of blood to your heart and enables doctors to plan how to correct those problems before they cause more trouble. These tests are mostly quite safe but occasional complications can occur. Your doctors will assess you carefully before deciding which of these types of test is most appropriate for you.
Myocardial contrast echocardiography involves injecting a substance that allows doctors to use echocardiography to see the flow of blood through the coronary arteries. This technique is becoming popular as a clinical tool in specialist hospitals but in most countries is not yet routinely available.
Radionuclide investigations involve injecting a small amount of a radioactive substance into your bloodstream and then using a special detection device to see where the substance is distributed around the body during an exercise test. Depending on the substance used and the techniques adopted this method can give information about the pumping performance of the heart or the supply of blood to the heart during exercise.
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