warning signs and symptoms Some arrhythmias don’t cause any symptoms. Others announce themselves quite clearly, perhaps with the distinct feeling that the heart is racing. Still other arrhythmias cause non heart-related symptoms, such as lightheadedness or dizziness. Most adults will, at some point, experience fleeting, harmless heart rhythm changes. Certain arrhythmias, especially those that last long enough to impact heart function, can be serious or even fatal. Here are some warning signs and symptoms: Palpitation or a Skipped Beat Fluttering Slow Heartbeat – Bradycardias Rapid Heartbeat – Tachycardias Almost Fainting – Presyncope Fainting – Syncope Palpitation or a Skipped Beat Although it may seem as if the heart missed a beat, really the heart has a premature heartbeat, almost an extra beat happening too soon, which may result in a pause – the "skipped beat." Back to top Fluttering A fluttering sensation is usually due to a series of "skipped beats" that occur in quick succession. Back to top Slow Heartbeat – Bradycardias If the heartbeat is too slow, usually considered a rate below 60 beats a minute, not enough oxygen-rich blood flows through the body. Some symptoms of a slow heartbeat are: Fatigue Dizziness Lightheadedness Fainting or near fainting Shortness of breath Back to top Rapid Heartbeat – Tachycardias When the heart beats too quickly, usually considered a rate above 100 beats a minute, the lower chambers, or ventricles, do not have enough time to fill with blood, so they cannot effectively pump blood to the rest of the body. When this happens, some people experience: Skipping a beat Beating out of rhythm Palpitations Rapid heart action Shortness of breath Chest pain Dizziness Lightheadedness Fainting or near fainting Chaotic, quivering or irregular rhythm Back to top Almost Fainting – Presyncope Sometimes people experience symptoms before they faint. Presyncope can be a sign of a heart rhythm disorder and should be evaluated carefully. Symptoms include: Dizziness, lightheadedness or vertigo Blurred or narrowed (tunnel) vision Sweating Nausea and/or vomiting Stomachache/abdominal discomfort Heart palpitations Headache Confusion and/or difficulty speaking clearly or coherently Back to top Fainting – Syncope Fainting related to a heart rhythm disorder is more likely to happen suddenly and without warning than fainting related to other causes, such as dehydration or low blood sugar. Any sudden lose of consciousness should be evaluated by a physician. In some cases, fainting is the only warning sign of an arrhythmia that could cause sudden cardiac arrest.