Electrocardiograms (ECGs) are simple tests that don't really require preparation in the sense of fasting, having a specific liquid intake, or other tasks that you face when taking something like a blood test. However, there are a few items that need to be addressed before the test so that your doctors see the most accurate results possible. The waves on an ECG, such as the QRS complex, can be affected by small things that you wouldn't normally think about.
Medications, Supplements, Teas, and Blood Levels
It's no secret that medications can affect tests, and the knowledge that supplements can do the same is quickly spreading. But two other related issues are also a concern. One is tea. Your average breakfast or afternoon black or green tea isn't such a problem, but herbal teas can be, and that includes iced teas that you're not drinking for any medicinal value. Hibiscus, for example, can affect blood pressure (in a good way; hibiscus tea may lower it slightly), so all those breezy hibiscus-mint concoctions you had over the summer, for example, could have been affecting your blood pressure. If you tend not to keep track of all the herbs in your teas, just let your doctor know that you drink store-bought and commercial (cafe) preparations, and let your doctor go from there.
Another issue is existing levels of minerals and vitamins in your body. For example, a potassium level that is too high or too low can skew ECGs. In an emergency, you won't have time to take a blood test before getting an ECG, but if there's an abnormal result, you might want to talk to your doctor about having a test done to see if your levels of potassium, sodium, and other minerals could have been a factor.
Temperature and Reassurance
If you move, your ECG can change. That's only natural since your heart reacts to how you move (that's why you have faster beating when you've been exercising, and so on). But that also means you have to avoid shivering, which can have a couple of causes. One is the room temperature. If you're cold, tell your doctor so that he or she can either raise the temperature in the room to a point where you aren't shivering or get you a blanket.
Another cause is fear; if you're dealing with new and strange problems, you could be very scared. Having the ECG tech talk you through the procedure, or having the tech use positive language so that you don't get even more worried by the tone of voice the tech uses, can help.
ECGs are simple tests. You don't have to worry about elaborate preparation. Just communicate with your doctor and the ECG tech to ensure that the test goes smoothly and does not make you feel nervous.