Arrhythmias are abnormal heart rhythms that occur when your heart muscle contracts too fast (tachycardia) or too slowly (bradycardia). Some arrhythmias are benign and need to be treated only if they cause symptoms. Others are life threatening and must be addressed even if they do not produce any symptoms.


Your heart’s precise rhythm is set by its own pacemaker or electrical system, which sends contraction signals to its four chambers. This results in coordinated contraction of the chambers and efficient delivery of blood. Typically, this electrical impulse is restarted 50 to 100 times per minute, establishing your normal heart rate.


An arrhythmia may produce: fatigue, dizziness, fainting, weakness, shortness of breath, palpitations, anxiety, chest discomfort or pain. Sometimes an arrhythmia does not produce symptoms. This does not mean that it is any less dangerous.


There are two types of tachycardias: supraventricular and ventricular. Both cause the heart to beat too fast.

Supraventricular tachycardias occur in the heart’s upper chambers and usually are benign. They begin and end suddenly.

Some forms of supraventricular tachycardia are more serious. These include atrial fibrillation, which causes the heart’s upper chambers to quiver — which can last for a few seconds, hours, or all the time. This may increase the risk of stroke and, therefore, merits medical attention.

Ventricular tachycardias (called VT or T-tach) occur in the heart’s lower chambers. They cause very fast but regular heartbeats, so the heart does not pump as efficiently. Symptoms include a pounding sensation, dizziness, or feeling faint. Ventricular tachycardia may worsen into another arrhythmia called ventricular fibrillation, in which the heart rhythm becomes so unstable that it does not beat but merely quivers and the heart stops pumping blood entirely. You suffer a temporary loss of oxygen and pass out. Typically, these arrhythmias occur in people who have other forms of heart disease, such as prior heart attacks or heart failure. Without emergency treatment, ventricular fibrillation can lead to sudden cardiac death.


A bradycardia occurs when your heart beats too slowly. The blood may not move through the heart and the body the way it should. This can cause dizziness and fainting. When the natural pacemaker cells do not function properly, signals are not being generated. In other cases, the signals are made properly but don’t travel normally — getting stopped before making it all the way through the chambers.


The first step is an electrocardiogram (ECG) which records short-term electrical activity of the heart. You may also need a Holter monitor, a portable device you wear while doing everyday activities. It records heart rhythm for 24 hours. If the symptoms are very infrequent, you may be given an event recorder to only record the rhythm when the symptom occurs. An ultrasound echocardiogram and a stress test also may be prescribed.


Some arrhythmias do not need treatment. Others benefit from medication to normalize the heartbeat or reduce the risk of blood clots. You may also be referred to an electrophysiologist for more extensive testing or treatment. Electrophysiologists are specially trained cardiologists who study the heart’s electrical conduction, then use medications, procedures, or devices to correct abnormal heart rhythms. These procedures include a Tilt table test, an electrophysiology study (EP study or EPS), cardioversion or implantation of a device to regulate rhythm (either a permanent pacemaker or a cardioverter-defibrillator).

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