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.

Figure 6-1 Catheter positions for routine electrophysiologic study. Multipolar catheters are positioned in the high right atrium near the sinus node, in the area of the atrioventricular (AV) node and His bundle, in the right ventricular apex, and in the coronary sinus.

Table 6-1 Clinical Applications of Electrophysiologic Studies

Diagnostic

• Diagnose sinus node dysfunction

• Determine site of AV nodal block

• Define cause of syncope of unclear origin

• Differentiate VT from SVT in cases of wide-complex tachycardia

• Define mechanism of SVT or VT and map site of origin of tachycardia

Therapeutic

• Guide drug therapy for sustained VT, aborted sudden death, or SVT

• Select appropriate candidates for cardioverter-defibrillator and anti-tachy cardiac pacing therapy

• Test efficacy of device therapy for ventricular tachyarrhythmias

• Select appropriate candidates for catheter ablative and surgical therapy

• Test efficacy of ablative and surgical therapies

Interventional

• AV nodal ablation or modification for atrial fibrillation

• Ablation for atrial tachycardia and atrial flutter

• AV nodal modification (slow-pathway or fast-pathway ablation)

• Accessory pathway ablation in WPW syndrome

• Ablation of ventricular tachycardia

Prognostic

• Risk stratification in asymptomatic WPW syndrome

• Risk stratification in patients after myocardial infarction

• Risk stratification in patients with nonsustained VT

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

Personnel

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.

Nurse-Technicians

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.

Biomed Tech

A biomedical engineer and/or technician should be available to the laboratory to maintain equipment so that it is properly functioning and electrically safe. Electrophysiologic procedures must be done by personnel who are properly trained in and who are dedicated to the diagnosis and management of arrhythmias. This opinion is shared by the appropriate associations of internal medicine and cardiology.

Equipment

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.

Figure 6-2 General setup of the equipment used for electrophysiologic studies.

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

Diagnostic Catheters

The hallmark feature of an electrophysiology catheter is the presence of at least two ring electrodes that can be used for bipolar and unipolar pacing and recording of local myocardial electrical activity. The material used to construct these catheters may be of the woven Dacron variety or synthetic materials such as plastic or polyurethane. The number of electrodes in these catheters can vary from 2 to 20 and the inter-electrode spacing can vary from 2 to 20 mm and the thickness can vary from 4 F to 7 F. The shape of these catheters can vary on the basis of the structures they are designed to map: the crista terminalis, the His bundle, the coronary sinus, or the pulmonary vein ostium. Typical electrophysiology catheters are shown in Figure 6-3.

Figure 6-3 A, Several types of multipolar catheters used in routine electrophysiologic studies. Note the difference in the number of electrodes and the differences in spacing between the electrodes among the various catheters. B, The proximal end of a hexipolar electrode catheter. The number on each pin corresponds to the electrode position at the tip of the catheter, with D representing the most distal electrode.

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.

Figure 6-4 Specialized large-tip catheter electrodes designed for ablative procedures.

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.

Carto

{Figure 6-5}

Figure 6-5 Cartoon illustrating principles of operation of the CARTO system, specifically how the catheter location is determined. The location pad is fixed beneath the patient table. The pad is constructed of three coils, which generate ultra low magnetic fields (1, 2, 3 kHz). The emitted fields possess well-known temporal and spatial distinguishing characteristics that “code” the mapping space around the patient’s chest. Sensing of the magnetic field by the location sensor (passive) enables the determination of the location and orientation of the catheter in six degrees of freedom.

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.

Figure 6-6 Ultra low external magnetic field emitter that is used in the CARTO system. This device is placed below the patient. The system comprises a miniature passive magnetic field sensor located at the tip of the catheter, an external ultralow magnetic field emitter, and a processing unit. The system uses the magnetic technology to accurately determine the location and orientation of the catheter in six degrees of freedom (x, y, z, roll, pitch, and yaw) and simultaneously records the intracardiac local electrogram from its tip. The three-dimensional geometry of the chamber is reconstructed in real time with the electrophysiologic information, which is color-coded, superimposed on the electroanatomical map.

Figure 6-7 Focal tachycardia image. The figure shows an electroanatomical map of the right and left atria along with the coronary sinus. The activation sequence pattern of an atrial tachycardia is shown, with red representing sites of early activation and blue and purple representing late sites. The activation pattern shows a focal arrhythmia arising from the anterior lip of the coronary sinus ostium. The maroon dots represent sites where catheter ablation was performed.

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).

Figure 6-8 An example of an left anterior oblique (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 this figure. 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.

(Courtesy St Jude Medical Inc.)

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.

Figure 6-9 Effect of filtering frequency on the His bundle electrogram. Pacing from the proximal coronary sinus is performed at a basic cycle length of 60 milliseconds. In each of the four panels, surface leads I, II, aVF, and V₁ are shown. A recording catheter is placed in the standard position to record the His bundle electrogram and recordings from the proximal, mid, and distal electrode pairs are displayed. A, His bundle electrograms where the signal is filtered between (30 HZ (high pass) and 500 HZ (low pass). B, Recording made between filter settings of 0.05 and 500 HZ. C, Between 30 and 1000 HZ. D, Between 100 and 500 HZ. The clearest recording of the His bundle electrogram occurs with a filtering of the signals below 30 HZ and above 500 HZ (A).

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.

Figure 6-10 Junction box/recording apparatus and stimulation apparatus. This picture shows the Prucka Cardiolab EP system used in our institution. Also seen within the white oval is a computerized stimulator manufactured by Micropace Inc. The junction box interfaces with the recording system and stimulator and thus allows us to change the pacing site without the need to disconnect catheters.

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.

Defibrillator

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.

Figure 6-11 Diagram of intracardiac defibrillation, which may be used when ventricular fibrillation is refractory to multiple transthoracic defibrillations. During the routine electrophysiologic (EP) study, anterior and posterior skin patches are attached by a connector to a standard defibrillator. When multiple transthoracic high-energy shocks fail to terminate ventricular fibrillation, the anterior patch may be disconnected and the distal pole of the right ventricular (RV) catheter attached to the defibrillator. High-energy shocks are delivered from the right ventricular catheter to the posterior patch.

(From Cohen TJ, Scheinman MM, Pullen BT, et al: J Am Coll Cardiol 18:1280-1284, 1991.)

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.

Remote Navigation Systems

With the advent of catheter ablation for AF, the duration of catheter ablation procedures saw a steep rise and operator fatigue became a significant issue. The ability to manipulate catheters in a precise manner during these procedures also began to gain importance. These factors led to the development of technology that allows the physician to manipulate the catheters in a very precise manner reproducibly and from a distance and thus possibly accelerate the workflow. The two leading technologies to achieve remote catheter navigation are the magnetic navigation system developed by Stereotaxis Inc and the robotic navigation system from Hansen Medical Inc. Most dedicated electrophysiology laboratories have acquired one of these two technologies and therefore a familiarity with these is essential.

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.

Figure 6-12 Stereotaxis laboratory. The figure shows an electrophysiology laboratory where the Stereotaxis Niobe system has been installed. The left arrow shows one of the two floor mounted magnets. The arrow on the right points to an electroanatomical map of the left atrium and pulmonary veins of a patient who underwent a catheter ablation procedure for atrial fibrillation. The system is designed to make manual catheter steering, which can be difficult and time consuming, unnecessary

(Image courtesy Drs. Jason Bradfield and Kalyanam Shivkumar, University of California at Los Angeles.)

Robotic Sheath Navigation

The Hansen Catheter Control System is designed to provide precise catheter control and 3D navigation. By bringing together robotic technology with computer movement algorithms, the remote control of catheters is made possible from a physician workstation in a location where radiation exposure is decreased. The advantage of this system is that the system is transportable and does not require construction of a specialized room. A key aspect of the system is an electromechanical catheter manipulator that responds to physician inputs from a workstation. A picture of an operator sitting at a Hansen workstation is shown in Figure 6-13.

Figure 6-13 Hansen Medical System. A picture of an operator sitting at a Hansen workstation is shown. Remote control of catheters is made possible from a physician workstation, with the intention of the system being to improve on manual catheter manipulation by providing greater dexterity and precision

(Courtesy Hansen Medical Inc, Mountain View, CA.)

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.

Pacemaker Systems Analyzer

In the implantation of pacemakers and defibrillators, a pacemaker systems analyzer (PSA) is crucial. Its circuitry replicates that of the pulse generator and the PSA will accurately predict the performance of the pulse generator. During our implants, we use the PSA provided by the manufacturer. The physician credentialing for pacemaker and defibrillator implantation procedures is controversial and in the recent past has been contentious as well. Studies show that in patients undergoing defibrillator implantation, as a group, electrophysiologists have fewer complications and better outcomes than cardiologists or thoracic surgeons.

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.

Preprocedural Nursing Considerations

Patient Preparations

Before device implantation procedures, patients are instructed to scrub and wash the neck, shoulders, and chest with a chlorhexidine-containing soap the evening before and on the morning of the procedure. Preoperative skin cleansing with chlorhexidine-alcohol is superior to cleansing with povidone-iodine for preventing surgical site infection especially with Staphylococcus aureus after clean-contaminated surgery. The male patients have their chest hairs clipped before the procedure. Although the administration of prophylactic antibiotics is controversial, we administer intravenous (IV) vancomycin immediately before the procedure. The patient should fast at least 6 hours before the procedure. An IV line is started on the same side of the planned procedure to facilitate venography.

Anticoagulation Issues

Device implantation in the anticoagulated patient has been controversial but is less so in the current age. Today, several investigations have demonstrated the safety of performing implantation procedures without interrupting Coumadin. In fact, it is safer to not discontinue Coumadin than it is to bridge the patient with heparin before and after the procedure. We continue maintenance anticoagulation for implant procedures especially if the patient has AF or prosthetic valves. The use of heparin postimplant is associated with more bleeding complications.

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	Identify signs and symptoms of cardiac or neurologic disease Identify factors known to exacerbate arrhythmias Determine details of syncopal events
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	Identify previous myocardial infarction Identify intraventricular conduction delays Identify prolonged QT interval Identify preexcitation syndromes
24- to 48-hr ambulatory ECG	Correlation of symptoms with ECG events Quantitation of ambient ectopy Identify diurnal variation in arrhythmia
Event recorder	Correlation of symptoms with ECG events
Head-up tilt-table testing	Diagnose vasovagal/vasodepressor syncope
Echocardiogram and radionucleotide ventriculography	Assessment of left ventricular and right ventricular size and function Detection of valvular pathology
Stress test (with or without perfusion scanning)	Detection of reversible ischemia Assessment of effects of catecholamines on arrhythmia induction
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,

Figure 6-14 Intracardiac electrograms recorded from various positions on a multipolar catheter positioned across the tricuspid valve. The numbers 1 to 5 refer to the intracardiac location of the catheters along with the corresponding electrograms; 1 represents the most distal location recording a large ventricular electrogram and no atrial electrogram, and 5 represents the most proximal location displaying a large atrial electrogram with a small ventricular electrogram. The His potential is observed when the catheter is in the area of the tricuspid annulus and the atrial and ventricular electrograms recorded are approximately of equal size (position 3).

(From Grossman W: Cardiac catheterization and angiography, ed 2, Philadelphia, 1974, Lea & Febiger.)

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.