Norfolk County Cardiologist Association
The 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. The cardiac electrical system is important because it controls the heart rhythm, and abnormalities in the electrical system are responsible for most heart arrhythmias.
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 tacycardia usually becomes clear.
What are some of the variations used with the EP study?
If the EP study uncovers the need for a permanent pacemaker, the pacemaker can often be inserted immediately, during the same procedure.
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. First, the cardiac electrical system is carefully mapped while the patient is in SVT, thus identifying the area responsible for causing the SVT. Ablation is then performed by passing radiofrequency energy through the tip of a special electrode catheter, thus cauterizing the culprit area.
If rapid forms of VT and/or ventricular fibrillation (VF) are identified during the EP study, treatment with antiarrhythmic drugs can be evaluated. A drug is administered, and an attempt is made once again to induce the arrhythmia. The goal is to find a drug that makes it impossible to induce an arrhythmia that had been inducible before the drug was given. This procedure, called serial drug testing, was common in the 1980s and early 1990s, but has fallen out of favor in recent years because drugs identified in this way are not always effective (and even one recurrence of VT or VF can be fatal.)
More commonly, patients who have inducible rapid VT or VF receive the implantable defibrillator. This device can now often be inserted in the EP laboratory, immediately following the EP study.
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.