The Electrophysiology Laboratory and Electrophysiologic Procedures

6 The Electrophysiology Laboratory and Electrophysiologic Procedures

Over the past two decades, the dedicated electrophysiology laboratory has evolved into a highly specialized procedure room where a variety of procedures are offered, ranging from diagnostic electrophysiology studies, curative catheter ablation procedures, implantation of loop recorders, pacemakers, defibrillators, and resynchronization therapy devices to extraction of chronic indwelling leads. This chapter discusses personnel, fluoroscopy, equipment, laboratory organization, and recording and stimulation apparatus, followed by a description of the electrophysiologic characteristics of common arrhythmias. The laboratory structure to facilitate implantation of pacemakers and defibrillators is also described. Although implantation of pacemakers and defibrillators is a very important function of the electrophysiology EP laboratory, this chapter introduces the physician and allied health personnel to the field of electrophysiology studies and catheter ablation of arrhythmias.

The electrophysiology study (EPS) is an invasive procedure that involves the placement of multipolar catheter electrodes at various intracardiac sites. Electrode catheters are routinely placed in the right atrium, across the tricuspid valve annulus in the area of the atrioventricular (AV) node and His bundle (a special part of the conduction system), in the right ventricle, in the coronary sinus, and sometimes in the left ventricle (Fig. 6-1). The general purposes of EPS are to characterize the electrophysiologic properties of the conduction system, induce and analyze the mechanism of arrhythmias, and evaluate the effects of therapeutic interventions. Invasive electrophysiology techniques and procedures are routinely used in the clinical management of patients who have supraventricular and ventricular arrhythmias (Table 6-1). In today’s laboratory, the use of computer-generated “electroanatomical maps” are very much a part of the jargon and even a novice must be able to recognize the color-coded activation patterns of common arrhythmias shown later in this chapter. Individuals seeking a more in-depth discussion of the procedures and concepts described should refer to the Suggested Readings section.

Table 6-1 Clinical Applications of Electrophysiologic Studies





AV, Atrioventricular; SVT, supraventricular tachycardia; VT, ventricular tachycardia; WPW, Wolff-Parkinson-White.


The most important aspects for the performance of safe and effective electrophysiologic procedures (especially for catheter ablations) are the presence and participation of dedicated personnel functioning as a seamless team, taking direction from the clinical electrophysiologist performing the procedure. The minimum personnel requirements include at least one physician, one to two nurses and technicians, an anesthesiologist on site or on standby, and a biomedical engineer (on the premises) to troubleshoot and repair equipment.

The clinical electrophysiologist is ultimately responsible for all aspects of the procedure and should be fully trained in an accredited electrophysiology fellowship program in all aspects of clinical cardiac electrophysiology. He or she should be a cardiologist who has spent preferably 2 years of additional training in an active electrophysiology laboratory and has met criteria for certification. The guidelines for training in clinical cardiac electrophysiology were developed by the American Heart Association and the American College of Cardiology in collaboration with the Heart Rhythm Society. The criterion for certification in this subspecialty has been established by the American Board of Internal Medicine. The skills clinical electrophysiologists possess should include the ability to implant devices, perform transseptal punctures, extract chronic indwelling pacemaker and defibrillator leads, and cannulate the pericardial space to map and ablate ventricular arrhythmias.


Two nurses and technicians or two “nurse-technicians” are preferable. These nurse-technicians must be familiar with all the equipment used in the laboratory and must be well trained in cardiopulmonary resuscitation (CPR). Most laboratories use two or three dedicated nurse-technicians. Their responsibilities include monitoring hemodynamics and rhythms, using the external defibrillator delivering antiarrhythmic medications and conscious sedation (nurses), and collecting and measuring data. They are also trained to respond to any emergent complications that arise during the study. The nurse is the main link between the patient and physician during the study in terms of the patient’s comfort level and clinical status. It is essential that the electrophysiologist and nurse-technicians function as a team, with full knowledge of the purpose and potential complications of each study because some of the complications are catastrophic and life threatening (especially in patients undergoing lead extractions and catheter ablation for ventricular tachycardia). EP nurses and technicians should be capable of performing in a deliberate, calm, and confident manner under conditions of extreme stress.

For the same reasons, an anesthesiologist and a cardiac surgeon should be available in the event that complications requiring thoracotomy or other heart surgery should arise. This is important in patients undergoing stimulation and mapping studies for malignant ventricular arrhythmias and, in particular, catheter ablation techniques. In addition, an anesthesiologist or nurse-anesthetist usually provides anesthesia support for implantable cardioverter-defibrillator (ICD) implantation and/or testing. It is our practice to perform procedures of prolonged duration such as prolonged ablations and so forth under general anesthesia. In patients with significant comorbid issues, conscious sedation is administered in our laboratory by the anesthesia service.


An electrophysiology laboratory is equipped with radiographic imaging systems, a recording and monitoring system, a stimulator, and all drugs and equipment required for ACLS (Fig. 6-2). Although a dedicated laboratory would be preferable, in many institutions, these procedures are carried out in the cardiac hemodynamic-angiographic catheterization laboratory. If used for pacemaker and defibrillator implantation procedures, the room should have air filtering equivalent to a surgical operating room. It is important that the EP laboratory have appropriate radiographic imaging equipment with an image intensifier capable of cinefluoroscopy and coronary angiography. Pulsed fluoroscopic systems allow for the production of radiation in short bursts instead of in a continuous manner. Use of pulsed fluoroscopy is a necessity to keep radiation exposure to a minimum. The fluoroscopic unit should be equipped with a cumulative timer that will remind the operator of each 5-minute period of fluoroscopy exposure and the total amount. To reduce radiation exposure, especially as the procedures get longer and more complex, there is a trend across all laboratories to increasingly rely on nonfluoroscopic imaging such as electroanatomical mapping and ultrasound imaging. The equipment must be capable of obtaining views in multiple planes with an installed biplane mode when possible.

Although expensive and elaborate equipment cannot substitute for an experienced and careful operator, the use of inadequate equipment may prevent adequate amounts of data from being collected and can make all the difference between success and failure. The arrhythmia targeted determines what equipment is required. A complete evaluation of most arrhythmias that may require activation mapping necessarily involves the use of multiple catheters, several recording channels, a programmable stimulator, and sophisticated computerized, three-dimensional (3D) mapping systems. Thus an appropriately equipped laboratory should provide all the necessary equipment for the most detailed study.

Electrode Catheters

Ablation Catheters

Ablation catheters of various designs allow the operator to map and to delivery energy in a very precise manner. The ablation catheters vary with respect to the length of the ablation/tip electrode ranging from 3.5 to 10 mm in length. Figure 6-4 shows commonly used ablation catheters. Notice that the tip of the catheter can be deflected to allow for the arrhythmogenic myocardium to be reached. Conventionally, the tip of the ablation catheter is longer than the electrode of a diagnostic catheter. This is to prevent overheating of the ablation electrode with consequent coagulum formation. Prevention of overheating of the ablation electrode can also be achieved by active cooling with saline irrigation. Catheters that deliver microwave, cryothermal, or ultrasound energy to destroy tissue are also being developed.

Electroanatomical Mapping Catheters

In the mid 1990s, a novel technology termed “nonfluoroscopic electroanatomical mapping” revolutionized the practice of interventional electrophysiology. Electroanatomical mapping systems integrate three functionalities, namely (1) nonfluoroscopic catheter localization in 3D space, (2) 3D display of activation sequences and of electrogram voltage, and (3) integration of this “electroanatomical” information with noninvasive images of the heart, i.e., computed tomography or magnetic resonance images or ultrasound images (image fusion). There are two leading mapping systems available and most laboratories use one or both of these. They are (1) the CARTO system manufactured by Biosense-Webster Inc and (2) the NAVX system manufactured by St Jude Medical Inc.


{Figure 6-5}

In the mid 1990s, a catheter was created that has the appearance of a standard ablation catheter with a magnetic sensor within the shaft near the tip (Biosense-Webster Inc). Together with a reference sensor, it can be used to precisely map the 3D spatial location of the catheter. The electroanatomical mapping system is called the CARTO system and it consists of the reference and catheter sensor, an external ultralow magnetic emitter (Figs. 6-6 and 6-7), and a processing unit. The amplitude, frequency, and phase of the sensed magnetic fields contain information to solve the algebraic equations yielding the precise locations (see Fig. 6-6) in three dimensions (x, y, and z axes) and orientation of the catheter tip sensor (roll, pitch, and yaw). An electrogram can also be recorded simultaneously in space, and thus an electroanatomical map can be generated. The catheter can also be moved without fluoroscopy thus decreasing radiation exposure. An example of atrial tachycardia that was arising from a focal point that was mapped and ablated successfully with the use of the CARTO system is shown in Figure 6-7 for focal tachycardia. A left anterior oblique (LAO) of an electroanatomical map of the right and left atria as well as the coronary sinus is shown. The activation data seen with the color scale show the arrhythmia to arise from the ostium of the coronary sinus.

Localisa and NAVX

This system was initially marketed under the name of Localisa and was subsequently integrated into the NAVX system. It uses three low-amplitude high-frequency current fields that are generated in three axes over the patient’s thorax to compute the position of an electrode in the thorax relative to a reference electrode that can be placed in the heart or on the patient’s thorax. Based on these measurements, the system then displays the position of any electrophysiology catheter (NAVX). The advantage of the Localisa or NAVX system is that multiple catheters can be displayed, and, unlike the CARTO system, they are not limited to the products of a single manufacturer. An example of an LAO cranial view of an electroanatomical map of the left atrium (blue shell) along with the four pulmonary veins and the left atrial appendage (green) constructed with NAVX is shown in Figure 6-8. Also seen are the coronary sinus catheter and the tip of the ablation catheter and a circular mapping catheter. This map was performed in a patient undergoing catheter ablation of atrial fibrillation (AF).

Junction Box and Recording Apparatus

This equipment consists of pairs of numbered multiple pole switches matched to each recording and stimulation channel and permits the ready selection of any pair of electrodes for stimulation or recording. Current computer junction boxes come in banks of 8 or 16. Nowadays, the signal processor (filters and amplifier), visualization screen, and recording apparatus are incorporated as a single unit in the form of a computerized system. The popular systems are manufactured by Prucka (GE), EP Medical (SJM), or Bard. Eight to 14 amplifiers should be available to process surface electrocardiogram (ECG) leads simultaneously with multiple intracardiac electrograms. The number of amplifiers can be as many as 128 in some systems. Intracardiac recordings must be displayed simultaneously with at least three surface ECG leads. Most computers allow several pages to be stored with one page displaying a 12-lead ECG. Thus one can always have a 12-lead ECG recorded simultaneously while the operator is observing intracardiac electrogram data. The amplifiers used for recording intracardiac electrograms must have the ability to have gain modification and alter both high and low band pass filters to permit appropriate attenuation of the incoming signals. For example, the His bundle electrogram is most clearly visualized when the signal is filtered between 30 or 40 Hz (high pass) and 400 or 500 Hz (low pass, Fig. 6-9). In addition, assessing unipolar electrograms also requires acquiring open filters (0.05 to 500 Hz). In our institution, we use a Prucka Cardiolab EP system.

Stimulation Apparatus

Most electrophysiology studies require a complex programmable stimulator that has (1) a constant current source, (2) minimal current leakage, (3) the ability to pace at a wide range of cycle lengths (100 to 2000 ms) from at least two simultaneous sites, (4) the ability to introduce multiple extrastimuli, and (5) the ability to synchronize the stimulator to appropriate electrograms during spontaneous and paced rhythms. The stimulator is equipped with dials or switches by which the pacing intervals and coupling intervals of the extrastimuli may be adjusted (Fig. 6-10). A junction box that interfaces with the recording system and stimulator facilitates changes in pacing site without the need to disconnect catheters. The stimulator should be able to deliver variable currents that can be accurately controlled, with a range from 0.1 to 10 mA. The ability to change pulse widths is also useful. The results of programmed stimulation can be influenced by the delivered current, and, for consistency and safety, stimulation is generally carried out at two and a half times diastolic threshold.

It is preferable that the stimulator, computerized data recorder, and other devices used in EP are permanently installed. In most laboratories, a stimulator and a computer system that modifies all input signals and stores them in an optical disc is used. All equipment must be grounded and other aspects of electrical safety must be ensured because even small amounts of leakage current can pass to the patient and can potentially induce arrhythmias. The equipment must be checked by a technical engineer so that leakage current remains less than 10 mA. A cartoon illustrating the organization of the relevant equipment during an EPS is illustrated in Figure 6-2.


A functioning defibrillator should be available at the patient’s side throughout all electrophysiology studies. A backup defibrillator is optimal in case of a rare but potentially disastrous failure of one defibrillator. The defibrillators should be tested before each study and equipped with an emergency power source. Many laboratories use commercially available R-2 pads, which are placed on the patient before the EPS procedure is begun. One pad is placed under the right scapula and the other on the anterior chest over the left ventricular (LV) apex and connected to the defibrillator with an adaptor. In rare instances in which transthoracic defibrillation fails to convert induced ventricular fibrillation, emergency defibrillation through an intracardiac electrode catheter may be effective in terminating the arrhythmia (Fig. 6-11). It is our practice to have biphasic defibrillators in our laboratories.

Because the physician’s attention is often focused on the stimulator and electrograms, he or she relies heavily on the nurse to monitor the patient’s condition and communicate significant changes. The nurse usually sits between the patient and the cardioverter-defibrillator and crash cart. The nurse monitors the patient’s blood pressure, heart rate, rhythm, and oxygen saturation via a pulse oximeter. The nurse administers drugs for diagnostic and therapeutic interventions during EPS and performs cardioversion or defibrillation when an induced hemodynamically unstable arrhythmia appears. Optimally, a second nurse is available during procedures to administer medications or to assist in technical aspects of the procedure.

Magnetic Navigation

The Stereotaxis system allows physicians to perform catheter ablation of cardiac arrhythmias with a greater degree of safety and precision by driving powerful magnets positioned near the patient with sophisticated software used by the physician. The magnets lead a soft catheter gently along this pathway by guiding its magnetic tip. This enables the physician to safely position the catheter in the precise location by the use of a joystick in the control room and thus minimize radiation exposure. The system uses two permanent magnets mounted on articulating or pivoting arms that are enclosed within a stationary housing, with one magnet on either side of the patient table, inside the EP laboratory. These magnets generate magnetic navigation fields that are less than 10% of the strength of fields typically generated by magnetic resonance imaging (MRI) equipment and therefore require significantly less shielding and cause significantly less interference than MRI equipment.

Because the working tip of the disposable interventional device is directly controlled by these external magnetic fields, the physician has the same degree of control regardless of the number or type of turns, or the distance traveled, by the working tip to arrive at its position in the blood vessels or chambers of the heart, which results in highly precise digital control of the working tip of the catheter. A picture of the Stereotaxis system from the University of California Los Angeles with one of the floor-mounted magnets is shown in Figure 6-12. Installing a magnetic navigation system requires that the catheterization laboratory be equipped with steel plates and specialized equipment to prevent the magnetic fields from interfering with other equipment.

Implantation of Pacemakers, Defibrillators, and Resynchronization Therapy Devices

Facilities, Personnel, and Equipment

In the early days, pacemaker implantation was performed by surgeons in the operating room. As the device underwent progressive miniaturization, the procedure could be performed without a thoracotomy and moved to the catheterization laboratory. The skills required also evolved to the ability to cannulate a central vein and the ability to place the lead against the appropriate myocardial location. With the advent of implantable defibrillators and resynchronization therapy devices, the operating physician had to be adept at cannulating the coronary sinus and other coronary venous branches, manipulating “over the wire” leads, and comfortable inducing ventricular fibrillation multiple times during a procedure. The need to perform high-quality coronary venograms in multiple planes reinforced the shift from the operating room to the EP laboratory.

The support personnel required for an implant procedure are the same as those for electrophysiology studies and ablations. They include a scrub nurse or technician familiar with the operating physician’s preferences, a circulating nurse, and an individual responsible for electrical testing. It is useful to have a cardiovascular radiology technician. The presence of a nurse to administer conscious sedation depends on whether an anesthesiologist or nurse anesthetist is present during the procedure. In some institutions, deep sedation for testing defibrillation thresholds is administered by the electrophysiologist.

In our institution, it is customary to have a representative of the pacemaker or defibrillator manufacturer present for clinical support. A well-trained representative has experience and knowledge of the company’s products and his or her support is very helpful in achieving a good procedural outcome.

Surgical Type of Sterile Environment

Early concerns about sterility are well founded. A defibrillator or pacemaker is a foreign body that is going to remain in place for several years, and, hence, infection is a primary concern. Generally, the operating room is considered to be a high sterile area and offers the best protection from infection. The catheterization laboratory is considered an intermediate sterile area and is a high traffic area but offers the advantage of high-quality radiography with high-resolution images, multiple projections, and image magnifications, along with the fact that these laboratories are fully equipped with all the necessary catheters, sheaths, and wires that may be required. The right combination for device implantation is a dedicated EP laboratory where the ventilation system meets standards for operating rooms and a rigid protocol for aseptic techniques is followed.

The importance of adequate lighting in these procedures cannot be overemphasized. Many of these procedures are performed on patients in whom antiplatelet and antithrombotic agents are not interrupted. To prevent pocket hematomas, it is important to be able to visualize the pulse generator pocket. Although not always available in every laboratory, a high-intensity head lamp is particularly useful, especially when inspecting into the pocket looking for bleeding vessels.

The electrocautery-surgery device involves the use of a pen that delivers alternating current in the radiofrequency range and creates resistive heating of tissues; it can be used for making incisions or for achieving hemostasis.

Clinical Evaluations of the Patient before Electrophysiology Procedures

The operating physician must comprehensively evaluate the patient before the study and plan the procedure on the basis of the specific needs of the individual patient. Whenever possible, ECG documentation of the clinical event should be reviewed. Some or all of the procedures listed in Table 6-2 may be included in this evaluation.

Table 6-2 Possible Components of Evaluation Before Electrophysiologic Testing

Procedure Purpose
History and physical examination

Neurologic evaluation (if history and physical suggest)  
Electroencephalogram Rule out seizure disorder
Computed tomography/magnetic resonance imaging Identify focal lesion
Carotid ultrasound Identify significant cerebrovascular disease
12-lead ECG

24- to 48-hr ambulatory ECG

Event recorder Correlation of symptoms with ECG events
Head-up tilt-table testing Diagnose vasovagal/vasodepressor syncope
Echocardiogram and radionucleotide ventriculography

Stress test (with or without perfusion scanning)

Cardiac catheterization Definition of coronary anatomy

ECG, Electrocardiogram.

Selected procedures may vary depending on the clinical presentation.

Any potentially reversible arrhythmogenic factors, such as electrolyte abnormalities or decompensated congestive heart failure,

should be corrected before the study is performed. All antiarrhythmic medications should be discontinued for at least five half-lives before the baseline study. For supraventricular tachycardia studies, medications influencing AV nodal conduction (e.g., beta-blockers, digoxin, and calcium channel blockers) should be discontinued.

Jun 5, 2016 | Posted by in CARDIAC SURGERY | Comments Off on The Electrophysiology Laboratory and Electrophysiologic Procedures

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