An electrophysiology (EP) study is used to evaluate and treat var-ious dysrhythmias that have caused cardiac arrest or significant symptoms. It also is indicated for patients with symptoms that suggest a dysrhythmia that has gone undetected and undiagnosed by other methods. An EP study is used to
· Identify the impulse formation and propagation through the cardiac electrical conduction system
· Assess the function or dysfunction of the SA and AV nodal areas
· Identify the location (called mapping) and mechanism dys-rhythmogenic foci
· Assess the effectiveness of antiarrhythmic medications and devices for the patient with a dysrhythmia
· Treat certain dysrhythmias through the destruction of the causative cells (ablation)
An EP procedure is a type of cardiac catheterization that is performed in a specially equipped cardiac catheterization labo-ratory. The patient is awake but lightly sedated. Usually a cathe-ter with multiple electrodes is inserted through the femoral vein, threaded through the inferior vena cava, and advanced into the heart. The electrodes are positioned within the heart at specific locations—for instance, in the right atrium near the sinus node, in the coronary sinus, near the tricuspid valve, and at the apex of the right ventricle. The number and placement of electrodes de-pend on the type of study being conducted. These electrodes allow the electrical signal to be recorded from within the heart (intracardiogram).
The electrodes also allow the clinician to introduce a pacing stimulus to the intracardiac area at a precisely timed interval and rate, thereby stimulating the area (programmed stimulation). An area of the heart may be paced at a rate much faster than the normal rate of automaticity, the rate at which impulses are spontaneously formed (eg, in the sinus node). This allows the pacemaker to become an artificial focus of automaticity and to assume control (overdrive suppression). Then the pacemaker is stopped suddenly, and the time it takes for the sinus node to resume control is assessed. A prolonged time indicates dysfunction of the sinus node.
One of the main purposes of programmed stimulation is to as-sess the ability of the area surrounding the electrode to cause a reentry dysrhythmia. One or a series of premature impulses is de-livered to an area in an attempt to cause the tachydysrhythmia. Because the precise location of the suspected area and the specific timing of the pacing needed are unknown, the electrophysiolo-gist uses several different techniques to cause the dysrhythmia during the study. If the dysrhythmia can be reproduced by pro-grammed stimulation, it is called inducible. Once a dysrhythmia is induced, a treatment plan is determined and implemented. If, on the follow-up EP study, the tachydysrhythmia cannot be in-duced, then the treatment is determined to be effective. Different medications may be administered and combined with electrical devices (pacemaker, ICD) to determine the most effective treat-ment to suppress the dysrhythmia.
Complications of an EP study are the same as those that can occur with cardiac catheterization. Because an artery is not always used, there is a lower incidence of vascular complications than with other catheterization procedures. Cardiac arrest may occur, but the incidence is low (less than 1%).
Patients who are to undergo an EP study may be anxious about the procedure and about its outcome. A detailed discussion involving the patient, the family, and the electrophysiologist usu-ally occurs to ensure that the patient is able to give informed con-sent and to reduce anxiety about the procedure. Before the procedure, patients should receive instructions about the proce-dure and its usual duration, the environment where the proce-dure is performed, and what to expect. Although an EP study is not painful, it does cause discomfort and can be tiring. It may also cause feelings that were experienced when the dysrhythmia oc-curred in the past. In addition, patients also are taught what will be expected of them (eg, lying very still during the procedure, reporting symptoms or concerns).
Patients need to know that the dysrhythmia may occur dur-ing the procedure, but under very controlled circumstances. It often stops on its own; if it does not, treatment is given to restore the patient’s normal rhythm. During the procedure, patients benefit from a calm, reassuring approach.
Postprocedural care includes restriction of activity to promote hemostasis at the insertion site. To identify any complications and to ensure healing, the patient’s vital signs and the appearance of the insertion site are assessed frequently.
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