Related Resources • Common heart tests • Cardiac arrhythmias • Implantable defibrillators

How is an EP study performed?

The patient is brought to the electrophysiology laboratory (a specialized catheterization laboratory) and placed on an examination table. After local anesthesia is given, electrode catheters are inserted into blood vessels in the groin, arm, or neck. (Catheters are inserted either through a small incision, or by means of a needle-stick. Sometimes, catheters are inserted from more than one site.) The catheters are advanced through the blood vessels to the heart. Generally at least two or three electrode catheters are inserted, and are positioned to specific locations within the heart.

Once positioned within the heart, the electrode catheters are used to do two main tasks: recording the electrical signals generated by the heart, and pacing from various locations within 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 cardiac arrhythmias can be fully characterized.

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

What kinds of arrhythmias can the EP study evaluate?

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

If the propensity for bradycardia is identified during the EP study, the need for a permanent pacemaker can be decided during the study.

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 mechanism of the tachycardia can usually be precisely identified. And once the mechanism is identified, the appropriate therapy for the tachycardia usually becomes clear.

How does the EP study help to direct treatment of arrhythmias?

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 baseline EP study. Once the EP study has confirmed the precise mechanism of the patient's tachycardia, a specialized electrode catheter is inserted, and the heart's electrical system is carefully mapped. Once the doctor identifies the precise area of the heart most responsible for causing the arrhythmia, radiofrequency energy through the tip of the catheter, thus cauterizing the culprit area. For the most common forms of SVT, ablation is successful in eliminating the arrhythmia in more than 95% of patients.

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" antiarrhythmic drug for patients with VT or VF, but today it is understood that no antiarrhythmic 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 are relatively safe, but because they are invasive procedures involving the heart, several complications are possible. Nobody should 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 the 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 1000.