context: Your heart is hard at work as it pumps blood and nutrients throughout your body. You can sometimes hear it or even feel it as it beats at a steady pace. It's got an even, reliable rhythm that's controlled by your body's own electrical system. When that system has issues, though, you get a change in your heart's rhythm that's called arrhythmia. If you have an arrhythmia, it doesn't necessarily mean you've got heart disease. There are many things that can cause your heart to flutter. It's possible to have a random arrhythmia even if your heart is healthy. If you do, talk to your doctor. Arrhythmias are caused by: Infection or fever Physical or emotional stress Diseases such as anemia or thyroid disease Drugs and other stimulants, such as caffeine, tobacco, alcohol, cocaine, amphetamines, and certain over-the-counter and prescription medications Your genes Some heart conditions A typical heart will beat at 60 to 100 times per minute. It can beat faster if you need it to during exercise or in a stressful situation. It can slow down while you sleep. Your heart is used to slowing down and speeding up. That's normal. When its rhythm is interrupted, you might not notice. Some people, however, can feel it when it happens. Common symptoms include: Palpitations, or "skipped beats" Thumping or fluttering in the chest Sensation of the heart racing Other things that might happen: Feeling faint or tired Light-headedness or passing out Shortness of breath Chest pain or discomfort You may have these sensations and have no arrhythmias. The symptoms may be from anxiety, stress, or other causes besides a problem with your heartbeat. There's a node in the upper right section of your heart that monitors your body's need for blood. It's called the sinoatrial ( SA) or sinus node, and it acts like a natural pacemaker. It's the main control and source of each heartbeat. It can speed up your heart rate when you need it, like when you exercise or get sick, or even when you feel happy. Your SA node sends out electrical impulses across the heart. These cause the chambers to contract at specific times, causing a heartbeat. Heart arrhythmias fall into two categories. One starts from inside the heart's lower chambers. Doctors call this kind "ventricular" because the lower chambers of the heart are the ventricles. The other kind starts outside or above the ventricles. You may hear these called "supraventricular" arrhythmias. The most common types of arrhythmia include: Premature atrial contractions. Doctors may call these " PACs" or " APCs." When your heart contracts earlier than expected, it adds an extra heartbeat. Supraventricular tachycardia or paroxysmal SVT. This is when your heart beats rapidly because of abnormal electrical impulses above the lower heart chamber. Sick sinus syndrome. This has nothing to do with the sinuses in your head. It's about your heart's SA node. Your electrical system fires abnormally, slowing down your heart rate. Atrial fibrillation. This happens when your heart sends electrical impulses at a fast rate, causing a fast and irregular heartbeat. Atrial flutter. Your heart misfires its electrical impulses, bringing on an irregular or fast heartbeat. Premature ventricular complex, or PVCs. Your heart fires an abnormal electrical impulse, causing an early heartbeat. Usually, the heart returns to its normal rhythm right away. Ventricular tachycardia. Your heart sends fast impulses and causes a very rapid heart rate. This is usually serious. Get medical help right away. Ventricular fibrillation. Electrical impulses start in a fast and disordered sequence, which causes your heart to lose its ability to beat and pump blood. This typically causes cardiac arrest. Supraventricular arrhythmias. These are more common, are generally temporary, and often aren't serious. They can create a sensation of a fast heart beat and dizziness. You may have noticed your heart racing, a fluttering in your chest, or a sensation that your heart skipped a beat. If this happens once or infrequently with no other symptoms, it's usually not serious. Talk to your doctor about your questions and concerns. If you get treatment and it doesn't help, make sure to let him know. If you have any of these symptoms, call 911 right away: Unexplained shortness of breath Light-headedness or feeling faint You feel that your heart is beating too slowly or too quickly Chest pain with any of these symptoms When your doctor checks you for heart rhythm disorders, he'll ask about your symptoms, give you a physical exam, and give you a few tests. An electrocardiogram ( EKG) will track and record your heart's rhythm to find out the type of disorder you have. It could take 24 hours or longer to find any problem. If the arrhythmia doesn't happen often, your doctor will give you a Holter monitor or an "event recorder," which you can turn on when you feel the symptoms. Your doctor might recommend an echocardiogram, which is an ultrasound of the heart. It gives a better picture of the structure and function of your heart, looking at the size of the chambers of your heart and its valves. In more serious cases, you might be tested with electrodes placed inside the heart. This is called an electrophysiologic study, and it is performed by an electrophysiologist. If you need treatment, the kind you get will depend on your case. You might need medication or surgery. For instance, a surgeon may place an implanted cardioverter defibrillator ( ICD) in your chest or belly. It will track your heart and reset your heart rhythm if it has a problem. Often, the ICD also works as a pacemaker to prevent you from developing a slow heart rate and to help your heart beat properly. You'll see your regular doctor, and probably a heart specialist, to make sure your treatment works well and to find out if the arrhythmia has returned.