Page 424 - Cardiac Nursing

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CHAPTER
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C C C C Cardiac Electrophysiology Procedures
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Susan Blancher
tfl
gy
a-
p
pr
y
(
di
ed
EP
)
ou
Th
Thee use of cardiac ellectro hysiiolloogy (EP) procedures includes di- outflow traact, corronary siinus, the His bundle reggion, and occa-
oc
,
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ac
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us
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le
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ph
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us
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er
In
um
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it
on
n,
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g
agnostic testing and interventional treatment procedures. In gen- si sionally the left atrium. In addition, a roving catheter can be used
e
an
b
l
g
erall, ddiagnostic EP studies are performedd to determine an ar- to to map intracardiac electroograms arising from different rregions of f
ap
f
di
ff
ro
m
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t
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g
ia
t
i
he
rd
y
ar
ca
hm
hm
ni
ia
ec
ha
kn
o
ow
sm
yt
ia
rh rhythmia diagnoosiis or EP mechanism off aa known arrhythmia. th thee heartt duriing taachhycardia. Occasionally, the left ventricle is
rh
yt
gn
d
m
n
ar
EP
di
el
me
am
ec
Interventional or therapeutic EP studies consist of endocardial used during a diagnosstic study for programmedd electtriic lal stimulla-
ti
s
d
no
ag
f
gr
ro
p
g
catheter ablation fof supravent iricullar andd ventricular arrhythmias. tion if VT cannot be induced from the right ventricle.
The placement of implantable cardioverter defibrillators (ICDs) After the catheters are in place and connected to the physio-
for the management of ventricular tachycardia (VT) and ventric- logic recording equipment, intervals are measured from both the
ular fibrillation (VF) is also an interventional EP procedure and is 12-lead electrocardiogram (ECG) and the intracardiac electro-
discussed in Chapter 32. Knowledge of electrocardiography (see grams in the baseline state (Fig. 18-2). The AH interval is a meas-
Chapter 15), normal cardiac activation (see Chapter 1), and car- urement of conduction time from the low right atrium through
diac activation during arrhythmias (see Chapter 16) is needed to the atrioventricular (AV) node to the His bundle and is an ap-
understand EP studies. proximation of AV node conduction time. The AH interval can
vary a great deal depending on the patient’s autonomic state and
2
measures approximately 55 to 120 milliseconds. The HV inter-
DIAGNOSTIC EP STUDIES val represents conduction time from the onset of His bundle de-
polarization to the onset of ventricular activity. The normal HV
3
interval measurement is 35 to 55 milliseconds. After baseline
Before an EP study, a patient needs to be prepared for the proce-
dure. This preparation and the techniques, complications, and in- recordings, various pacing techniques may be performed to assess
dications of EP studies are presented here. the patient’s electrical conduction system. Refractory periods for
the atrium, AV node, and ventricle are recorded. The presence of
retrograde or ventricular–atrial conduction is noted, as is the acti-
Patient Preparation vation sequence. Attempts to induce and document the arrhyth-
Preparation for EP procedures is similar to that for cardiac mia using the introduction of extrastimuli in either the atrium or
catheterization (see Chapter 20). Patients are kept fasting and the ventricle are then made. Intravenous isoproterenol or epi-
usually sedated during EP studies. The degree of sedation depends nephrine may be used to help induce arrhythmias or reveal acces-
on the type of study being performed and the preferences of the sory pathway (AP) or slow pathway conduction.
center performing the procedures. A peripheral intravenous line is The patient must be adequately prepared before the study and
required for administration of medicine. Systemic anticoagulation should understand that arrhythmia induction is often one of the
may be used during EP studies to decrease the incidence of primary goals of the study. The electrophysiologist attempts to
1
thromboembolic complications. Appropriate emergency and re- gather as much information as possible depending on the type of ar-
suscitation equipment is required for all EP procedures. rhythmia induced and how well it is hemodynamically tolerated.
Special physiologic recording equipment is able to document si-
Techniques multaneously every beat in 12-lead ECG and intracardiac electro-
gram format. Induced arrhythmias can then be reviewed and ana-
During invasive EP testing, spontaneous and pacing-induced in- lyzed after they are terminated. It is important to note the method
tracardiac and surface electrical signals are recorded. The normal of arrhythmia termination. Tachycardias may be self-terminating or
timing and sequence of electrical activation can be observed and require antitachycardia pacing to stop them. Occasionally, it is nec-
measured during a normal or baseline rhythm. Abnormal timing essary to cardiovert or defibrillate the patient to stop the arrhyth-
and electrical activation sequences are recorded and studied dur- mia. It is usually necessary to wait until the patient loses conscious-
ing tachyarrhythmias. Programmed electrical stimulation may ness before defibrillation to prevent painful shock in an awake state.
also be used to induce and analyze paroxysmal arrhythmias that If the patient is hemodynamically stable during a ventricular
are the same as or similar to a patient’s clinical arrhythmia. 2 arrhythmia, attempts to map its origin can be performed, partic-
Flexible catheters with at least 2 and up to 10 electrodes are in- ularly if ablation is planned (see the section titled “Interventional
troduced percutaneously. The catheters are advanced using fluo- EP and Catheter Ablation”). Atrial arrhythmias are usually well
roscopy into the heart. The right and left femoral, subclavian, in- tolerated and allow for extensive mapping. Recordings are made
ternal jugular, and median cephalic veins are the most commonly at various locations in the heart and compared with a reference
used venous access sites. One to several catheters may be placed signal, either a surface ECG lead or a stable intracardiac electro-
on
ig
study
to
1)
type
-
18
of
the
depending on the type of study to be performed (Fig. 18 1). TheThe gram The site of earliest activ ation is closest to the site wher e
(F
depending
formed
per
be
gram. The site of earliest activation is closest to the site where thethe
usual intracardiac recording sites include the high right atrium, arrhythmia originates. Occasionally, the clinical arrhythmia cannot
right atrial appendage, right ventricular apex, right ventricular be induced or is not sustained long enough for adequate mapping.
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