Electrophysiology Study (EPS)

An electrophysiology study, or EP study, examines the heart's electrical system directly. Thin, flexible catheters with electrodes at the tip are guided through a vein — usually in the groin — into the heart, where they record signals from inside the chambers with a precision no surface EKG can match.

The study is diagnostic, but it is frequently the first half of a treatment: once an abnormal circuit is located, a catheter ablation to eliminate it is often performed in the same session. That is usually discussed and consented for in advance.

• The precise origin and mechanism of a fast rhythm such as SVT, atrial flutter or ventricular tachycardia
• Whether an accessory electrical pathway is present, as in Wolff-Parkinson-White syndrome
• Whether the heart's own pacemaker or conduction system is failing, in unexplained fainting
• The risk of a dangerous ventricular arrhythmia, informing whether a defibrillator is needed
• Whether a rhythm can be provoked at all — sometimes the important answer

Expect to be at the facility for most of the day; the study itself commonly runs one to three hours, longer if an ablation follows.

You will have nothing to eat or drink after midnight, and your care team will tell you which medications to hold — antiarrhythmic drugs are often stopped several days beforehand, since they would suppress the very rhythm the study is trying to provoke.

You lie on a table with monitoring patches applied, and an IV provides sedation. Most EP studies are done under conscious sedation: you are drowsy and comfortable, and many people remember little of it. The groin is numbed, catheters are placed through a vein, and X-ray guidance and electrical mapping systems track their position.

The team then paces the heart through the catheters — delivering small, precisely timed electrical impulses to try to trigger your arrhythmia deliberately, under controlled conditions. You may feel your heart race or thump during this, which is expected and is the point of the study. A medication such as isoproterenol is sometimes given to make the rhythm easier to provoke.

The catheters are removed and firm pressure is held over the groin site to seal it. You lie flat for several hours to prevent bleeding — this is usually the least comfortable part of the day. Most patients go home the same evening or the next morning.

For about a week, avoid heavy lifting and strenuous activity. Some bruising and tenderness at the groin is normal. Call your care team about increasing pain, expanding swelling, a lump that grows, or bleeding that does not stop with pressure.

Serious complications are uncommon. They include bleeding or a blood vessel injury at the access site, and less frequently injury to the heart or to the normal conduction system — which can require a pacemaker. Your electrophysiologist will discuss the risks that apply to your specific case.