An electrophysiology study (EP study) is a procedure in which a thin tube (catheter) is inserted into a vein or artery (e.g., in the groin) and guided to the heart. The catheter is tipped with an electrode that is connected to an electrocardiograph (EKG) machine. Once inside the heart, it can perform highly specific measurements of the heart’s electrical activity and pathways. Specifically, the catheter is fed into the upper chambers of the heart (the atria), the lower chambers of the heart (the ventricles) or guided to the site of the heart’s natural pacemaker (the sinoatrial node). 

Once in place, the electrode is used to take a series of detailed measurements, tracing the progress of the electrical current through various portions of the heart's electrical conduction system. During a healthy heartbeat, an electrical signal arises from the sinoatrial node, which lies in the upper part of the right atrium. From there, the electrical signal travels through the atria, causing them to contract. The signal is next gathered at the atrioventricular node, which lies in the junction of the atria and ventricles, or upper and lower portions of the heart. From there, the signal travels through the ventricles along prescribed pathways, causing them to contract and pump blood into the arteries. The EP study is capable of measuring electrical activity very specifically in each of these areas, thus allowing physicians to exactly diagnose any abnormalities in the movement of electricity through the heart that might result in (arrhythmias).

During an EP study, the physician will also stimulate the heart to beat according to prescribed testing protocols. This may include inducing premature heartbeats, as well as specific kinds of arrhythmias. By doing this, the physician will be able to measure how well the heart's conduction system is functioning and possibly pinpoint the exact problem area. In some cases, treatment follows immediately after the irregular heartbeat is located using an ablation catheter. This instrument allows physicians to destroy the abnormal areas that are causing the arrhythmia.

EP studies can be used to diagnose the cause of abnormally slow heart rhythms (bradycardias) or abnormally fast heart rhythms (tachycardias). They are usually performed before patients undergo surgery to receive a pacemaker or implantable cardioverter defibrillator.

A newer type of catheter may help make the EP study more accurate in diagnosing paroxysmal (intermittent) atrial fibrillation. It is called the supreme spiral SC catheter. Its spiral-shaped tip allows physicians to more accurately map abnormal areas of the left atrium (the upper left chamber of the heart).

In addition, a new navigation system is being tested to increase the effectiveness of EP studies. The physician-directed, computer-controlled magnetic navigation system may assist in guiding a catheter into the heart.