Cardiac arrhythmia covers a very large number of very different conditions. The most common symptom of arrhythmia is an abnormal awareness of heartbeat, called palpitations. These may be infrequent, frequent, or continuous. Some of these arrhythmias are harmless (though distracting for patients) but many of them predispose to adverse outcomes.
Some arrhythmias do not cause symptoms, and are not associated with increased mortality. However, some asymptomatic arrhythmias are associated with adverse events. Examples include a higher risk of blood clotting within the heart and a higher risk of insufficient blood being transported to the heart because of weak heartbeat. Other increased risks are of embolisation and stroke, heart failure and sudden cardiac death.
If an arrhythmia results in a heartbeat that is too fast, too slow or too weak to supply the body’s needs, this manifests as a lower blood pressure and may cause lightheadedness or dizziness, or syncope (fainting). Some types of arrhythmia result in cardiac arrest, or sudden death. Medical assessment of the abnormality using an electrocardiogram is one way to diagnose and assess the risk of any given arrhythmia.

State of the art Texas Cardiac Arrhythmia Institute (TCAI) at St. David’s Medical Center