An arrhythmia is an abnormal heart rhythm. They can occur at any age, but become more common as we get older. If severe, the heart may not pump enough blood into the body. Symptoms can be mild such as a heart “fluttering” feeling, or severe such as causing fainting, dizziness, shortness of breath or cardiac arrest. An electrocardiogram is typically used to diagnose arrhythmias, and just knowing how to take your pulse can help you monitor them. Most arrhythmias are harmless and left untreated, but serious ones can be treated with medication, medical devices and nonsurgical procedures.