Electrophysiology (EP) Study

Normally, electricity flows throughout the heart in a regular, measured pattern. This electrical system brings about heart muscle contractions. A problem anywhere along the electrical pathway causes an arrhythmia, or heart rhythm disturbance. By accurately diagnosing the precise cause of an arrhythmia, it is possible to select the best possible treatment.

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Why an EP Study

While electrocardiograms (ECGs) are important tests of the heart’s electrical system, they are brief tests that record only the events that occur while the tests are running. Arrhythmias, by their very nature, are unpredictable and intermittent, which makes it unlikely that an ECG or electrocardiogram will capture the underlying electrical problem. Even tests that stretch over longer time lengths, such as Holter monitoring, may not capture an event.

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During an EP study, a specially trained cardiac specialist may provoke arrhythmia events and collect data about the flow of electricity during actual events. As a result, EP studies can help locate the specific heart tissue that gives rise to the abnormal electrical impulses that cause arrhythmias. This detailed electrical flow information provides valuable diagnostic and, therefore, treatment information.

 

The Value of an EP Study

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An electrophysiologic, or EP, study provides information that is key to diagnosing and treating arrhythmias. EP studies most often are recommended for patients with symptoms indicative of heart rhythm disorders or for people who may be at risk for Sudden Cardiac Death. Although it is more invasive than an electrocardiogram (ECG) or echocardiogram, and involves provoking arrhythmias, the test produces data that makes it possible to:

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• Diagnose the source of arrhythmia symptoms

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• Evaluate the effectiveness of certain medications in controlling the heart rhythm disorder

 

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• Predict the risk of a future cardiac event, such as sudden cardiac death

 

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• Assess the need for an implantable device (a pacemaker or ICD) or treatment procedure (catheter ablation)

 

An Overview of the Procedure

While ECGs are non-invasive, an EP study is invasive. The study is performed after giving local anesthesia and conscious sedation (twilight sleep) to keep the patient as comfortable as possible. The procedure involves inserting a catheter – a narrow, flexible tube – attached to electricity monitoring electrodes, into a blood vessel, often through a site in the groin, and winding the catheter wire up into the heart. The journey from entry point to heart muscle is navigated by images created by a fluoroscope, an x-ray-like machine that provides continuous, “live” images of the catheter and heart muscle. Once the catheter reaches the heart, electrodes at its tip gather data and a variety of electrical measurements are made. These data pinpoint the location of the faulty electrical site. During this “electrical mapping,” the cardiac arrhythmia specialist may instigate, through pacing (the use of tiny electrical impulses), some of the very arrhythmias that are the crux of the problem. The events are safe, given the range of expertise and resources close at hand and are necessary to ensure the precise location of the problematic tissue.

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Once the damaged site or sites are confirmed, the specialist may administer different medications or electrical impulses to determine their ability to halt the arrhythmia and restore normal heart rhythm. Based on this data, as well as information acquired before the study, sometimes the specialist will proceed to place an implantable cardioverter device (ICD) or a pacemaker or will perform cardiac ablation. In any case, the information proves useful for diagnosis and treatment.

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Throughout the procedure, the patient is sedated but awake and remains still. Patients rarely report pain, more often describing what they feel as discomfort. Some are able to watch the procedure on monitors and occasionally ask questions. Others sleep. The procedure usually takes about two hours. The patient remains still for four to six hours afterward to ensure the entry point begins to heal properly. Once mobile again, patients may feel stiff and achy from lying still for hours.

 

The Importance of the Flow of Electricity

Each heart has it’s own normal rhythm brought about by the seamless flow of electrical impulses throughout the organ. This electrical flow begins in the heart's natural “pacemaker” (also know as the sinoatrial node or sinus node) in the upper right heart chamber, the right atrium. The electricity flows through the upper chambers (atria), crosses the bridge between upper and lower chambers (atrioventricular node) and travels to the lower chambers (ventricles.) The passage of electricity culminates in a carefully coordinated contraction of heart muscle that pushes blood through the human body. Problems in the precise flow of electricity are the cause of arrhythmias.

 

Who Performs the Test and Where

Since potentially dangerous arrhythmias are provoked during an EP study, it’s crucial that specialized staff are present to handle all situations. A cardiac electrophysiologist, with advanced training in the diagnosis and treatment of heart rhythm problems, performs the EP study. The cardiac electrophysiologist leads a team of specially trained health care professionals, technicians and nurses, who assist during the procedure. The team performs the EP study in an electrophysiology laboratory, or EP lab, a well-equipped, controlled clinical environment usually located within a hospital or clinic. As a result, the test is quite safe and complications are rare.

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