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Figure 6-17 Example of an implantable cardiac monitor. (EnSite, Velocity,
Quartet, SJM Confirm and St. Jude Medical are trademarks of St. Jude
Medical, Inc. or its related companies. Reprinted with permission of St. Jude
Medical, © 2015. All rights reserved.)
The Electrophysiology Laboratory and Electrophysiologic Procedures
Facilities, Personnel, and Equipment
In earlier days, surgeons in the operating room performed pacemaker
implantation. 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
include the ability to cannulate a central vein and place the lead
against the appropriate myocardial location. With the advent of
implantable defibrillators and resynchronization therapy devices, the
operating physician needed to be adept at cannulating the coronary
sinus and other coronary venous branches, manipulating “over the
wire” leads, and comfortable inducing VF during a procedure. The
need to perform high-quality coronary sinus venograms in multiple
planes reinforced the shift from operating room to EP laboratory.
The support personnel required for an implant procedure are the
same as for EPSs 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 the EP lab, a representative of the pacemaker or defibrillator
manufacturer is often 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. However, responsibility for all aspects of the procedure
remains with the operating physicians. Consideration of procedural
liability dictates no hands-on involvement of nonhospital employees
participating in more than a consultative role.
Pacemaker Systems Analyzer
For implantation of pacemakers and defibrillators, a pacemaker
systems analyzer (PSA) is crucial. Because the circuitry replicates that
of the PG, the PSA will accurately predict the performance of this
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
also been contentious. Studies show that in patients undergoing defibrillator implantation, as a group, electrophysiologists are associated
with fewer complications and better outcomes than cardiologists or
thoracic surgeons.
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The Electrophysiology Laboratory and Electrophysiologic Procedures 293
Surgical Type of Sterile Environment
Early concerns about sterility are well founded. A defibrillator or pacemaker is a foreign body that will remain in place for several years, and
hence, infection is a primary concern. Generally, the operating room
is considered to be a highly sterile area and offers the best protection
from infection. The catheterization laboratory is considered to be
an intermediate sterile and 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 of the necessary catheters, sheaths,
and wires that may be required. The right combination for device
implantation is a dedicated EP laboratory, in which the ventilation
system meets standards for operating rooms, and a rigid protocol for
aseptic techniques.
The importance of adequate lighting for these procedures cannot
be overemphasized. Many such 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 PG pocket. Although not always available in every laboratory, a
high-intensity headlamp is particularly useful, especially when inspecting the pocket for bleeding vessels.
An 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
achieving hemostasis.
Preprocedural Nursing Considerations
Patient Preparations
The evening before and morning of device implantation procedures,
patients are instructed to scrub and wash the neck, shoulders, and
chest with a chlorhexidine-containing soap. Preoperative skin cleansing with chlorhexidine-alcohol is superior to cleansing with povidoneiodine for prevention of surgical site infection, especially with
Staphylococcus aureus
have their chest hairs clipped before the procedure, and all patients
should fast for at least 6 hours before. Although the administration of
prophylactic antibiotics is controversial, we administer intravenous
(IV) antibiotics immediately before the procedure. The IV line is
started on the same side of the planned procedure to facilitate venography, if necessary.
Anticoagulation Issues
Device implantation in the anticoagulated patient has been controversial but is less so nowadays. Of late, several investigations have demonstrated the safety of performing implantation procedures without
interrupting warfarin (Coumadin). In fact, it is safer to continue Coumadin than 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.
The use of novel oral anticoagulants is relatively new, and little
data are available regarding the risk of bleeding with implants in
patients using these medications. For patients undergoing implantation of a cardiac device, it is our practice to interrupt the use of these
medications in the perioperative period.
after clean-contaminated surgery. Male patients
Pacemaker Troubleshooting
1. Failure to deliver output
2. Failure to capture
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Box 6 -2 Gathering Information for Effective Pacemaker
1. Indication(s) for pacing
2. Implantation date of each component
3. Pacemaker/leads model
4. Current programmed parameters
5. Battery volt age/impedance
6. Lead impedance(s)
7. M easured parameters
8. Chest x- ray if necessar y
3. Oversensing
4. Undersensing
5. Pacemaker-mediated tachycardia (PMT)
6. Lead dislodgement
7. Pacemaker syndrome
8. Runaway pacemaker
understanding its “normal function” is essential, as is obtaining basic
information about the patient, implanted pacemaker leads, and programmed parameters (Box 6-2). Believe it or not, considering that so
many special features are available in different pacemakers, it is very
easy to misinterpret normal pacemaker functions. Obtaining a thorough history is crucial to determine the course of a problem.
mise determines the urgency for repairing a problem. If the patient is
severely bradycardiac and a pacemaker programmer is unavailable,
transcutaneous or temporary pacing may be lifesaving. If a pacemaker
malfunction occurs shortly after implantation, consider poor lead
placement, lead dislodgement, loose set screws, and lead reversal,
rather than lead conductor/insulation fracture and battery depletion.
magnet will terminate the tachycardia. In very rare cases of a “runaway
pacemaker” (caused by a major pacing circuit component failure),
urgent surgical PG removal is necessary.
devices is tracking AF or flutter at an upper tracking rate. Magnet
placement over the PG drops the pacing rate to a “magnet rate” for that
specific device until programmed parameters are changed (i.e., activating a mode switch feature or using nontracking modes, such as
[DDI] or [VVI]). Tachycardia in sensor-driven pacemakers may simply
be remedied by turning the sensor “off.”
The Electrophysiology Laboratory and Electrophysiologic Procedures
Troubleshooting
Before attempting to troubleshoot a pacemaker malfunction,
The presence or absence of symptoms or hemodynamic compro-
In most cases of pacemaker-driven tachycardia, application of a
The majority of pacemaker-driven tachycardia by DDD or VDD
Electrocardiogram Assessment
It is critical to understand the basic timing of a dual chamber pacemaker (Fig. 6-18).
1. Look for pacing spikes.
2. If spikes are present, measure rate interval, presence of evoked
response (complete paced beats), fusion beats, and pseudofusion
beats.
3. If absent, apply a magnet (mode will be switched to AAI/VOO or
DOO) to see spikes.
Causes of Absent Pacing Output
1. PG output failure
2. Oversensing (can be diagnosed by applying a magnet)
AP APVP VP
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The Electrophysiology Laboratory and Electrophysiologic Procedures 295
Base rate interval
V–A Interval
Paced AV delay
PVARP
A
TARP
B
C
D
E
F
Figure 6-18 A, Basic timing in dual chamber pacemakers. TARP, Total
atrial refractory period; V-A, ventricular-atrial. B, Atrial oversensing, confirmed
by marker channels showing atrial sensing (AS) markers without P waves.
C, Ventricular oversensing. Observe marker channel for ventricular sensing
(VS) without a QRS. D, Loss of ventricular capture (arrow). E , Atrial undersensing; P waves without markers. F, Pacemaker Wenckebach (WB). Occurs
when the atrial rate increases but does not exceed the 2 : 1 block point.
Continued
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G
H
The Electrophysiology Laboratory and Electrophysiologic Procedures
Atrial undersensing
Placing a magnet on the device
I
Figure 6-18, cont’d
maker pace in the atria and ventricle (DOO). Arrow, Placing of a magnet on
the device. I, Example of DDIR pacing mode: The response to sensing is to
inhibit atrial output. No SAV is started, the ventricle is paced at the lower
rate, and if af ter a V– A interval there is no AS, then AP/VP and PAV occur.
DDIR is not appropriate for this patient due to a complete heart block (CHB).
AS, Atrial sensing; PMT, pacemaker-mediated tachycardia; SAV, sensed
atrioventricular.
G, Atrial undersensing. H, Magnet makes the pace -
Placement of a magnet on the PG is the next step. If spikes are
seen, oversensing is the issue. If spikes are still absent, either the
pacemaker is not putting out a pulse or the pulse does not reach the
heart.
Pulse Generator Output
Failure Causes
1. Battery depletion
2. Component failure
3. Electrocautery or defibrillator over or near the PG
4. Therapeutic radiation therapy over or near the PG
Noncapture Causes*
1. Low-output/high-capture threshold/exit block
2. Lead dislodgement
3. Lead conductor or insulation fracture
4. Loose set screws
5. Severe metabolic derangement or drugs
*Artificial noncapture: Pacing in the refractory period due to undersensing.
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The Electrophysiology Laboratory and Electrophysiologic Procedures 297
Undersensing Causes
(Undersensing Causes Overpacing)
1. Poor lead positioning
2. Lead dislodgement
3. Lead conductor/insulation fracture
4. Infarction of tissue near lead tip
5. Safety pacing
6. (DVI) mode
7. Ectopies with short amplitude
8. Severe metabolic derangement
9. Defibrillation over or near pacemaker PG
Action needed: increase pacemaker sensitivity, change the sens-
ing mode to unipolar mode, and, if necessary, repair or replace lead.
Oversensing Causes (Oversensing
Causes Underpacing)
1. Myopotentials
2. Cross talk
3. Lead conductor/insulation fracture
4. Electromagnetic interference
5. T-wave oversensing and far-field sensing
6. Loose set screw
To repair, decrease the sensitivity. For T-wave oversensing and
far-field sensing, we recommend prolonging the refractory period.
The sensing mode can be switched from the unipolar to bipolar
setting. As is the case with unipolar sensing, the “larger antenna” is
capable of causing oversensing. If leads are defective, lead repair or
replacement is curative.
Pacemaker Syndrome
Pacemaker syndrome is seen in patients with normal sinus rhythm
who have an inhibited VVI pacemaker or in those with dual chamber
pacemakers if the atrial lead does not appropriately sense or capture
the atrium.
Once atrial contribution/kick is lost, cardiac output diminishes
and the patient may experience dyspnea, fatigue, palpitations, chest/
neck/throat pulsations, and even syncope (as a result of atrial contraction against closed tricuspid and mitral valves [Cannon A waves]).
In patients with VVI pacemakers, we recommend allowing more
time to be spent in intrinsic normal sinus rhythm by lowering the
pacing rate. If this is not possible, upgrade to a dual chamber pacemaker. In patients with dual chamber pacemakers who have problems
with atrial leads, reprogramming atrial lead parameters should resolve
the issue; if not, atrial lead replacement is recommended.
Pacemaker-Mediated Tachycardia
Premature ventricular contraction (PVC), premature junctional contraction (PJC), or loss of atrial sensing or capture can cause PMT. With
retrograde conduction of a ventricular ectopy to the atrium after completion of the postventricular atrial refractory period (PVARP), the
retrograde “P” is sensed by the pacemaker, which in turn starts an AV
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The Electrophysiology Laboratory and Electrophysiologic Procedures
delay after which a ventricular paced beat is forced. This beat can
continue at the maximum rate of the upper tracking rate (PMT).
PMT can be terminated with the following actions:
1. Application of a magnet over the PG
2. Retrograde V–A conduction block
3. Programming a longer PVARP so that the retrograde P falls within
the PVARP
Different manufacturers have different PMT remedies, such as
PVARP extension for one beat after a PVC or DVI pacing for one beat
after PVC.
Cross Talk
Cross talk occurs when the ventricular channel senses the atrial pacing
spike and interprets it to be an intrinsic ventricular event, in which
case ventricular output is inhibited. In patients who are pacemaker
dependent and have no underlying escape mechanism, cross talk
causes asystole, which may be fatal (on the ECG, one sees an atrial
spike followed by P waves without a ventricular output/pacing spike).
In some cases, simply programing the atrial impulse to lower
amplitude or decreasing ventricular sensitivity can remedy the
problem. At times, increasing the blanking period is necessary.
Safety pacing is another remedy for cross talk. Allow a brief
period of ventricular sensing early after atrial pacing spike delivery
(this interval follows the blanking interval). If an event is sensed during
this interval, the pacemaker will force a ventricular paced beat with a
short AV delay of 100 to 120 msec (Fig. 6-19).
A
V
H
3
V
RBB
A
RB
2
V
1
200 msec
A
V
4
SN
A
V
5
Figure 6-19 Intracardiac electrograms recorded from various positions on
a multipolar catheter positioned across the tricuspid valve. Numbers 1 to 5
refer to the intracardiac location of the catheters along with the correspond ing electrograms; 1, most-distal location recording a large ventricular electrogram and no atrial electrogram; 5, 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). A , Atrium; Ao, aorta; AVN, atrioventricular node;
CS, coronary sinus; H, His; HB, His bundle; MS, membranous septum;
PA, pulmonary artery; RB, right bundle; RBB, right bundle branch; SN, sinus
node; V, ventricle. (From Grossman W: Cardiac catheterization and angiography, ed 2, Philadelphia, 1974, Lea & Febiger.)
Ao
MS
CS
PA
HB
AVN
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The Electrophysiology Laboratory and Electrophysiologic Procedures 299
Table 6 -2
Possible Components of Evaluation Before
Electrophysiologic Testing*
Procedure Purpose
Histor y and physical
examination
Neurologic evaluation Perform if history and physical suggest to
Electroencephalogram Rule out seizure disorder
Computed tomography/
magnetic resonance
imaging
Carotid ultr asound Identify significant cerebrovascular
12-lead ECG Identify previous myocardial infarction
24- to 48 -hour ambulator y
ECG
Event recorder Correlation of symptoms with ECG events
Head-up tilt-table testing Diagnose vasovagal/vasodepressor
Echocardiogram and
radionucleotide
ventriculography
Stress test (with or without
perfusion scanning)
Cardiac catheterization Definition of coronary anatomy
ECG, Electrocardio gram; LV, left ventricular; Q–T, inter val from star t of Q wave to end
of T wave; RV, right ventricular.
*Selected procedures may var y dep ending on clinical presentation.
Identify signs and symptoms of cardiac or
neurologic disease
Identify factors known to exacer bate
arrhy thmias
Determine details of syncopal events
rule out neurologic disease
Identify focal lesion
disease
Identify intraventricular conduction delays
Identify prolonged Q –T interval
Identify preexcitation syndromes
Correlation of symptoms with ECG events
Quantitation of ambient ectopy
Identify diurnal variation in arrhythmia
syncope
Assessment of LV and RV size and function
Detection of valv ular pathology
Detection of reversible ischemia
Assessment of ef fects of catecholamines
on arrhythmia induction
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, review ECG documentation of the clinical event. Some or all of the procedures listed in
Table 6-2 may be included in this evaluation.
Any potentially reversible arrhythmogenic factors, such as electrolyte abnormalities or decompensated congestive HF, should be corrected before the study is performed.
Discontinue all antiarrhythmic medications for at least five halflives before the baseline study. For supraventricular tachycardia (SVT)
studies, discontinue medications influencing AV nodal conduction
(e.g., β
-blockers, digoxin, and calcium channel blockers).
Premedication
The patient should have nothing by mouth after midnight except for
essential cardiac medications, which may be taken with a small
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amount of water. The patient may be lightly sedated with IV diazepam
or midazolam. In long diagnostic studies or in catheter ablation cases,
more intensive levels of sedation are usually required. IV fentanyl and
midazolam achieve somnolence in the patient during lengthy ablation
procedures. However, excessive sedation may influence the ability to
induce arrhythmias in some individuals.
Arterial and Venous Access
Routine diagnostic EPS involves stimulation and recording of electrical activity from the right side of the heart. Venous access may be
obtained from the femoral, subclavian, internal jugular, or antecubital
veins. A routine initial diagnostic EPS usually involves insertion of at
least three catheters, most commonly via the femoral veins. These
large veins easily permit the introduction of three 5-F to 8-F catheters
per vein. The number of catheters required and venous access selected
depend on the type of study being performed and the data being collected. Mapping of a left-sided bypass tract may necessitate catheterization of the left side of the heart for precise mapping.
For patients requiring beat-to-beat assessment of the hemodynamic effects of an induced arrhythmia, an arterial line may be placed.
To completely evaluate a patient with Wolff-Parkinson-White (WPW)
syndrome, the physician may have to access the LV for stimulation or
recording of intracardiac electrical activity. If arterial catheterization
is necessary, administration of IV heparin is mandatory. Patients
undergoing prolonged studies involving venous access or those with
a history of venous thromboembolism should also receive heparin.
Study Protocol
Although details of the protocol vary depending on the indication for
the EPS and the information being obtained, most studies involve the
recording and measurement of spontaneous intracardiac events and
observation of the effects of programmed electrical stimulation. An
initial study usually takes approximately 2 hours and depends on the
complexity of the case. Possible components of the initial comprehensive EPS are listed in Box 6-3.
Box 6 -3 Possible Components of Comprehensive Initial
Electrophysiologic Study*
Measurement of basic intervals
Determination of sinus node function
Determination of atrial, AV nodal, His-Purkinje, and ventricular conduction
and refractoriness
Identification of presence of dual AV nodal pathways
Identification of presence, location, and electrical proper ties of accessor y
AV pathways
Attempts to induce SV T
Attempts to induce V T
Determination of mechanism of induced arrhythmias
Mapping of origin site(s) of induced arrhy thmias
Determination of effect of IV antiarrhythmic drugs on induced tachycardia
Determination of efficacy of anti-tachycardia pacing for induced tachycardia
AV, Atrioventricular; I V, intravenous; SVT, supraventricular tachycardia; VT, ventricular
tachycardia.
*The actual procedure varies depending on the individual case; not all par ameters
are assessed in all cases.
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The Electrophysiology Laboratory and Electrophysiologic Procedures 301
Positioning of Catheters
The RA is easily accessible by any venous access. The most common
site for stimulation and recording is the high posterior lateral wall in
the region of the sinus node. The potential is most easily found with
a catheter introduced by the femoral approach and passed into the
RA across the tricuspid valve and into the RV. The catheter is withdrawn across the tricuspid valve with the application of a slight degree
of clockwise torque that tends to keep the catheter in contact with the
septum (see Fig. 6-21). A hexapolar or octapolar catheter in the His
position may be used so that electrical activity from multiple electrode
pairs can be recorded, and the one showing the most stable and consistent His potential may be displayed. If multiple attempts to record a
His potential with one catheter are unsuccessful, a differently shaped
or steerable catheter with a deflectable tip may be used. In most
patients, a His potential can be recorded successfully.
Usually, the LA is approached indirectly by recording in the coronary sinus. Cannulation of the coronary sinus os can be achieved from
the femoral, left subclavian, or right or left internal jugular approaches.
The appropriate position of the coronary sinus catheter is verified fluoroscopically in the LAO and right anterior oblique positions. The catheter curves upward toward the left shoulder in the LAO projection and
is posteriorly oriented in the lateral projection. On the ECG, atrial and
ventricular electrograms are recorded, with the timing of the LA electrograms appearing later than the high RA electrogram. Direct recording of electrical activity from the LA is possible in patients with a
patent foramen ovale or atrial septal defect or by a trans-septal
approach.
In most baseline studies, a catheter is placed in the RV apex. For
ventricular stimulation protocols, a second ventricular catheter is
sometimes placed in the RV outflow tract, although most operators
prefer to reposition the catheter from the apex to the outflow tract. The
order in which the catheters are placed in the right side of the heart
varies among operators, and no particular order is mandatory. In
ommended that the RV apical catheter be positioned first to ensure
adequate ventricular pacing in the event of catheter-induced trauma
to the right bundle, which may result in complete heart block (CHB)
while the His catheter is being positioned.
Catheterization of the LV may be necessary in patients with VT
or preexcitation syndromes. The LV is most commonly accessed by
the retrograde arterial approach for mapping procedures. Fluoroscopy
that permits views in multiple planes is essential to ensure accurate
positioning of the catheter. Stimulation may also be performed from
the LV in cases in which patients with clinically documented sustained
VT have arrhythmias that are noninducible with use of the standard
protocol from the RV. To avoid inadvertent cannulation of the coronary
arteries, the operator safely prolapses the catheter across the aortic
valve. In patients with atrial septal defects, patent foramen ovale, or
undergoing trans-septal punctures, the LV may be approached through
the LA and mitral valve.
Measurement of
Conduction Intervals
After the catheters are positioned, basic conduction intervals are measured, including the basic sinus cycle length (A-to-A interval), P-wave
duration, A–H interval, His spike duration, and H–V interval (Fig. 6-20).
Measurements from the surface ECG, including the P–R, QRS, and Q–T
intervals, are also recorded. Conduction interval measurements and
refractory period measurements should be made at a paper speed of
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