Studying the Heart's Electrophysiology

Surgeon holding pacemaker
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The cardiac electrical system is important because it controls the heart rhythm and because abnormalities in the electrical system are responsible for most heart arrhythmias. An electrophysiology study (EP study) is a special catheterization test in which electrode catheters (flexible, insulated wires with metal electrode tips) are inserted into the heart in order to study the cardiac electrical system.


How Is an EP Study Performed?

If your doctor has referred you for an EP study, you will be brought to the electrophysiology laboratory (a specialized catheterization laboratory) and lie down on an examination table. You will be given local anesthesia, and possibly a mild sedative, and then electrode catheters will be inserted into one or more blood vessels. (Catheters are inserted either through a small incision or by means of a needle-stick, usually in the arm, groin or neck. Most often two or three catheters are used, and they may be inserted from more than one site.) Using fluoroscopy (similar to an x-ray), the catheters are advanced through the blood vessels and positioned in specific areas within the heart.

Once they are appropriately positioned, the electrode catheters are used to do two main tasks: to record the electrical signals generated by the heart and to pace the heart. (Pacing is accomplished by sending tiny electrical signals through the electrode catheter.) By recording and pacing from strategic locations within the heart, most kinds of cardiac arrhythmias can be fully studied.

Once the procedure is completed, the catheter(s) are removed. Bleeding is controlled by placing pressure on the catheterization site for 30 to 60 minutes.

What Kinds of Arrhythmias Can an EP Study Evaluate?

An EP study can help to evaluate both bradycardias (slow heart arrhythmias) and tachycardias (rapid heart arrhythmias).

 If an EP study reveals a significant propensity for bradycardia, a permanent pacemaker may be required.

Tachycardias are assessed by using programmed pacing techniques to induce (i.e., to start up) the tachycardia. If tachycardias can be induced during the EP study, then by studying the electrical signals recorded from the electrode catheters, the precise cause of the tachycardia can usually be identified. Once this is accomplished, the appropriate therapy for the tachycardia usually becomes clear.

How Does an EP Study Help Direct Treatment for Arrhythmias?

There are a few ways an EP study can help you and your doctor make treatment decisions. Treatment options that may be considered based on the results of an EP study include: 

  • Insertion of a pacemaker: If the EP study confirms the presence of significant bradycardia, a permanent pacemaker can often be inserted immediately, during the same procedure.
  • Ablation: If supraventricular tachycardia (SVT) — and some forms of ventricular tachycardia (VT) — are found, radiofrequency ablation is often the treatment of choice. The ablation procedure is usually carried out during the same procedure, immediately following the EP study. You can read more about ablation therapy online.
  • Implantable defibrillators: If rapid forms of VT and/or ventricular fibrillation (VF) are identified during the EP study, most commonly an implantable defibrillator is the treatment of choice. This device can now often be inserted in the EP laboratory, immediately following the EP study. In earlier years, the EP study was used to identify the "best" anti-arrhythmic drug for patients with VT or VF, but today it is known that no anti-arrhythmic drug is as effective as the implantable defibrillator in preventing sudden death from these arrhythmias.

What Are the Risks of Having an EP Study?

The potential risks of having an EP study are similar to those of having a cardiac catheterization.

These procedures are relatively safe, but because they are invasive procedures involving the heart, several complications are possible. You should not have an EP study unless there is a reasonable likelihood that the information gained from the procedure will be of significant benefit.

Minor complications include minor bleeding at the site of catheter insertion, temporary heart rhythm disturbances caused by the catheter irritating the heart muscle and temporary changes in blood pressure.

More significant complications include perforation of the heart wall (causing a life-threatening condition called "cardiac tamponade"), extensive bleeding or (because potentially lethal arrhythmias are being induced) cardiac arrest. The risk of dying during an EP study is less than 1 out of 1,000.


Rahimtoola, SH, Zipes, DP, Akhtar, M, et al. Consensus statement of the Conference on the State of the Art of Electrophysiologic Testing in the Diagnosis and Treatment of Patients with Cardiac Arrhythmias. Circulation 1987; 75:III3.