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Diagnostic Electrophysiology Studies

What is an Electrophysiology Study?


A diagnostic electrophysiology study (EP study) is a procedure your cardiologist might recommend to investigate such symptoms as syncope (fainting), pre-syncope (dizziness), shortness of breath or palpitations (the sometimes unpleasant awareness of an abnormal heart beat). Your cardiologist might also recommend an electrophysiology study if you have a heart condition that makes a cardiac arrest more likely or for further investigation of an abnormal heart rhythm that has been detected through monitoring (such as on an ECG [electrocardiogram] or a Holter monitor). Electrophysiology studies can identify if you have a ‘short circuit’ involving the upper chambers of the heart that can cause supraventricular tachycardia (SVT), a ‘short circuit’ in the lower chambers of the heart that can cause a ventricular arrhythmia or cardiac arrest and if the hearts normal conduction system if functioning properly. 


An electrophysiology study is performed in a similar way to a coronary angiogram except catheters (thin tubes) are passed up to the heart through the femoral vein and not the femoral artery at the top of the leg. With the guidance of x-ray (usually) these catheters are advanced to the right side of the heart and are placed at the apex of the right ventricle, within the coronary sinus (a vein that runs behind the heart), next to the AV node (the hearts normal conduction system) and possibly at the top of the right atrium. These catheters can sense the electrical activity of the heart wherever they are placed and can also pace the heart to make it go faster and try to bring on abnormal heart rhythms. If an abnormal heart rhythm if found at the time of electrophysiology study then often this can be treated with an ablation (cauterisation) at the same time (see related sections on ablations).


Electrophysiology studies are generally performed with local anaesthesia and twilight sedation. This is because arrhythmias are often less frequent when people are sedated or asleep due to changes in hormone levels and heart cell function. A diagnostic electrophysiology study will generally take less than thirty minutes to complete and patients will usually go home a few hours later. With an EP study there is a 1:1000 risk of a potentially serious complication such as stroke, heart attack or bleeding around the heart requiring drainage. For further information please visit or read other sections about ablation procedures on this site. 

Heart Diagram EPS.jpg

Above is a cartoon of the heart showing the normal conduction system in yellow. The normal conduction system of the heart is studied using three or four electrical catheters passed up through the femoral vein at the top of the leg. Catheters are shown here as black lines with small white electrodes. A catheter is placed at the apex (tip) of the right ventricle, through the coronary sinus (a vein which runs behind the heart) and beside the hearts normal conduction system (the atrio-ventricular or AV node). These catheters can pace the heart from different positions to bring on abnormal heart rhythms and can sense the electrical activity of the heart wherever they are placed.  

EP Study.jpg

Above is an x-ray of the heart showing four diagnostic electrophysiology catheters (similar to the previous cartoon). Similar to the picture above there is a catheter in the coronary sinus (a vein behind the heart), in the right ventricle and next to the AV node. There is also a catheter placed in the high right atrium in this picture. 

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