It sounds like you or your doctor
is concerned that you may have an arrhythmia. An arrhythmia is an abnormal heart rhythm that can cause the heart to run too fast, too slow, or irregular. They can be felt by the person experiencing them, or can be completely without symptoms. If the arrhythmia is fast, you may feel your heart racing, or may feel lightheaded. All arrhythmias are caused by abnormal electrical activity in the heart. Thus the way we look for them is through the electrocardiogram (EKG).
Arrhythmia diagnostics start by a physician getting EKG and looking for any abnormalities. This involves just placing some pads on your chest hooked up to some electrodes. Often the EKG is normal, because it doesn't always show abnormalities when you are not actually having the arrhythmia. When this happens, the doctor may send you home with a Holter monitor
. This is basically a portable EKG recorder, which records all your heart electrical activity over many days. This increases the chances that the arrhythmia would be found. Unfortunately, there are no x-rays that can look for an arrhythmia.
The type of physician you need to see about this is a cardiologist
. He or she can perform this testing and see if you need any treatment. Good luck.