Answer to: What is an EP study?

The Electrophysiology Study
A catheter study for diagnosing and treating cardiac arrhythmias

By DrRich

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 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.

I hope that helps.

~ Dominique ~

3 Comments

Comment on article

by ElectricFrank - 2008-03-29 01:03:11

Thanks for posting the article on EP studies. As usual the procedure is put in the best light with only a passing reference to the potential issues. Here are a few thoughts.
1. The EP study itself isn't any more risky than having a pacemaker implanted. It involves inserting electrodes into the heart as we do with a pacer. The main difference is that an external "pacemaker" is hooked to the leads to make measurements and possibly stimulate the heart.
2. The risky part comes with what may happen as a result of the study. As you can see from the article, oblation is becoming the treatment of choice over meds. The problem is that a successful oblation requires finding the correct locations to cauterize (read "destroy"). This is a bit of a gamble as there is no going back. Once the tissue is destroyed it is gone forever.
3. There are several reasons for an unsuccessful outcome. One is that even the EP finds the source of the arrhythmia there is no way of knowing what the effect of oblating it will be. It may stop the problem or it may irritate it into something worse. The second problem is in hitting the spot. The EP has electrode leads inside a beating heart and is trying to hit a small exact spot on its wall. What are the chances of missing and oblating good tissue, thus causing new problems?

So my take is this: oblation is a useful procedure in some cases where it is the only alternative. But like a lot of other procedures, there is big money in it and the biomedical manufacturers are pushing in the same way the drug companies are pushing their wares. I keep seeing folks on this forum getting excited about being scheduled for an oblation that is going to fix all their problems. Then in a few weeks they are unhappy because now they are "totally pacemaker dependent" and feeling worse.

As for the 1 out of a 1000 dying during an EP study, I don't consider that as a small thing. to put it in perspective, the next time you are at the airport waiting for your fight to leave, look around. For every 5 or so planes leaving the gate someone would die (based on 200/plane). And if 1 of 1000 die then how many have bad outcomes, but live.

Sorry to be so negative,

frank

I would also add

by turboz24 - 2008-03-29 10:03:51

"oblation is a useful procedure in some cases where it is the only alternative. But like a lot of other procedures, there is big money in it and the biomedical manufacturers are pushing in the same way the drug companies are pushing their wares."

Perpetual drug use to control the arrythmia's also carry it's side effects, temporary and permanent. I just had my procedure last week and it was for the most part successful. I hopefully will not have to rely on high doses of antiarrythmia drugs to control my VT's (hopefully no drugs at all).
I felt that the oblation was worth the risk considering the side effects of 99% of the drugs used in my case.

It really depends on each individual, what their arrythmia is, how the drugs affect their life, their age, activity levels, etc.

Oblation vs drugs

by ElectricFrank - 2008-03-30 01:03:00

I agree. Properly used both can be very helpful. If the oblation works it is better in the long run than meds. It is just all too easy for a doc to become complacent about serious treatments. It's human nature. That's where most airplane accidents originate from. Take off in the middle of a thunder storm hundreds of times and get away from it and pretty soon the pilot isn't concerned about the one that is different.
My approach is that I am the person who is most interested in me so I question everything the doc wants to do. Then when I am convinced I go for it.

best,

frank

You know you're wired when...

You fondly named your implanted buddy.

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