Cardiac dysrhythmia (also known as arrhythmia or irregular heartbeat) is any of a large and heterogeneous group of conditions in which there is abnormal electrical activity in the heart. The heartbeat may be too fast or too slow and may be regular or irregular. A heartbeat that is too fast is called tachycardia, and a heartbeat that is too slow is called bradycardia. Although many arrhythmias are not life threatening, some can cause cardiac arrest.
Arrhythmias can occur in the upper chambers of the heart (atria) or in the lower chambers of the heart (ventricles). Arrhythmias may occur at any age. Some are barely perceptible, whereas others can be more dramatic and can even lead to sudden cardiac death.
Some arrhythmias are life-threatening medical emergencies and can result in cardiac arrest. Cardiac arrhythmias are one of the most common causes of death when traveling to a hospital. Others cause symptoms, such as an abnormal awareness of heartbeat (palpitations), and may be merely uncomfortable. These palpitations have also been known to be caused by atrial/ventricular fibrillation, wire faults, and other technical or mechanical issues in cardiac pacemakers/defibrillators. Still others may not be associated with any symptoms at all, but may predispose the patient to potentially life threatening stroke or embolism.
The term sinus arrhythmia refers to a normal phenomenon of mild acceleration and slowing of the heart rate that occurs with breathing in and out. It is usually quite pronounced in children and steadily decreases with age. This can also be present during meditation breathing exercises that involve deep inhaling and breath-holding patterns. Proarrhythmia is a new or more frequent occurrence of pre-existing arrhythmias, paradoxically precipitated by antiarrhythmic therapy, which means it is a side effect associated with the administration of some existing antiarrhythmic drugs, as well as drugs for other indications. In other words, it is a tendency of antiarrhythmic drugs to facilitate emergence of new arrhythmias. Some arrhythmias are minor and can be regarded as normal variants. In fact, most people will on occasion feel their heart skip a beat or give an occasional extra strong beat; neither of these is usually a cause for alarm.