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Fig. 11.7 Rhythm on a stress test of a patient with CPVT
K. Allshouse
Pearls
• QTc=QT/√R-R.
• LQTS1=KCNQ1 gene mutation, events with
exertion.
• LQTS2=KCNH2 gene mutation, events with
startle.
• LQTS3=SCN5A gene mutation, events with
sleep.
• Beta blockers for all Long QT-Nadolol or
Propranolol are best.
• Brugada-Type 1 pattern in V1, V2-3rd or 4th
decade of life, more in males.
• CPVT-VT with adrenaline-RYR2 or CASQ2.
Further Reading
1. Moss AJ, Adams FH. Cardiac channelopathies,
syncope and SCD (Chapter 20). In: Heart disease
in infants, children and adolescents. Philadelphia:
Wolters Kluwer; 2022. p. 534–50.
2. Wilde AAM, Ackerman MJ.Beta blockers in the treatment of congenital LQT syndrome: is one beta-blocker
superior to another. JACC. 2014;64(13):1359–61.
3. Ackerman MJ. Genetic purgatory and the cardiac
channelopathies: exposing the variants of uncertain/unknown signicance issue. Heart Rhythm.
2015;12(11):2325–31.
4. Ackerman MJ, et al. HRS/EHRA expert consensus statement on the state of genetic testing for the
channelopathies and cardiomyopathies. Europace.
2011;13(8):1077–109.
5. HRS/EHRA/APHRS expect consensus statement on
the diagnosis and management of patient with inherited primary arrhythmia syndromes. 2013.
6. Cho Y. Left cardiac sympathetic denervation: an
important treatment option for patients with hereditary
ventricular arrhythmias. J Arrhythm. 2016;32(5):340–
3. Published online 2015 Oct. 29. https://doi.
org/10.1016/j.joa.2015.08.002.
7. Schwartz PJ, Crotti L, Insolia R. Long-QT syndrome: from genetics to management. Circ Arrhythm
Electrophysiol. 2012;5(4):868–77. https://doi.
org/10.1161/CIRCEP.111.962019.
Introduction toCardiac Ablation
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KristaAllshouse
12
An electrophysiology study (EPS) is a cardiac
procedure performed in a specialized lab by a
cardiac electrophysiologist to diagnose and treat
arrhythmias. Prior to the procedure, patients are
sedated using conscious sedation or general anesthesia, access sites are sterilely prepped, and
catheters are placed via the left and right femoral
veins (and potentially other veins such as the
internal jugular vein) into specic areas of the
heart. These may include the high right atrium,
HIS bundle area, coronary sinus, right ventricle,
and may also be placed into the left heart via a
puncture of the atrial septum for left-sided
arrhythmias (transseptal puncture) (Fig. 12.2).
An arterial line may also be placed for blood
pressure monitoring. Systemic heparin is used for
anticoagulation during the procedure while catheters are in the body. Fluoroscopy is sometimes
used for catheter placement as well. These catheters are attached to the recording systems for
signal analyzation (Fig. 12.1). Most procedures
are also performed with electroanatomic mapping systems which use a combination of magnetic sensors and impedance measurements
within intracardiac catheters. External references
to triangulate catheter position within the heart
are used to generate three-dimensional cardiac
models. Electrical measurements are tracked
K. Allshouse (*)
Atrium Health, Levine Childrens’ Congenital Heart
Center, Charlotte, NC, USA
e-mail: Krista.Allshouse@atriumhealth.org
based on catheter position to dene impulse
propagation in the heart.
Baseline recordings of the intracardiac electri-
cal signals are taken in sinus rhythm (Fig.12.1).
Normal cardiac conduction properties are measured such as the conduction through the AV
node and His bundle. Diagnostic pacing maneuvers are then carried out to test the conduction
system and induce arrhythmias. These can identify the presence of conduction pathways that
may mediate arrhythmias, such as a slow pathway within the AV node or an accessory atrioventricular pathway in WPW. Sympathomimetic
drugs such as isoproterenol or dobutamine can
also be used to support blood pressure and help
with arrhythmia induction. Additionally, mapping catheters can be used to measure the electrical potentials of specic areas of myocardium to
identify signals or scar tissue which may form an
arrhythmic substrate. This mapping can be done
endocardially in the right heart, via trans-atrial
septal puncture or retrograde aortic access in the
left heart, and epicardially via subxiphoid access.
A hybrid procedure involving all the mapping
options may be needed as well. These may help
dene the mechanism of arrhythmia and guide
treatment.
Once a specic arrhythmia is found, ablation
may be undertaken with radiofrequency (heat
energy) or cryoablation (freezing energy). The
choice of modality used depends on the specic
arrhythmia and where the ablation site is anatom-
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023
R. Musialowski, K. Allshouse (eds.), Cardiovascular Manual for the Advanced Practice Provider,
https://doi.org/10.1007/978-3-031-35819-7_12
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Fig. 12.1 EP recording system screen with surface EKG leads on top (white), coronary sinus catheter recordings in
green, HIS bundle recording in yellow, and right ventricle recordings in red
K. Allshouse
Post-procedurally, catheters are removed, and
hemostasis is obtained using a variety of methods
including manual compression, temporary skin
sutures, and closure devices. A period of bedrest
is generally required. Depending on the procedure type and duration, the patient may be discharged the same day or the following morning.
Immediately post-procedure, the patient will be
closely monitored including evaluation of peripheral pulses in the legs, access site assessments,
vital signs, and neurologic evaluations to make
sure there are no complications. Post procedure
labs may be ordered per physician protocol and
patient should be monitored on telemetry and
have a post procedure EKG completed.
The risks of these procedures may include
groin bleeding/hematoma formation, pseudoaneurysm, retroperitoneal bleeding, stroke, cardiac perforation, arrhythmia requiring cardioversion, or
death. Specic types of ablation procedures may
Fig. 12.2 Fluoroscopy image of catheter placement in
the heart: high right atrium (HRA), coronary sinus (CS),
His bundle (His), and right ventricle (RV) [1]
also carry unique risks. For example, atrial brillation ablation is associated, rarely, with atrioesophageal stula (AE) in which esophageal
injury during ablation leads to an esophageal- left
ically located. Post-ablation testing is then completed to make sure the conduction system
remains unaffected, rule out additional arrhythmias, and to make sure the ablated arrhythmia is
terminated.
atrial stula. Generally presenting 2–4weeks post-
ablation, aorto-enteric stulas are life- threatening
and prompt recognition increases survival Right
phrenic nerve injury is possible with atrial brilla-
tion ablation as well as right atrial ablation in spe-
12 Introduction toCardiac Ablation
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129
cic areas. Epicardial ablation can be associated
with abdominal organ injury due to subxiphoid
access. Ablation of AV nodal re- entrant tachycardia and WPW can be associated with heart block
requiring permanent pacemaker.
References
1. Wenzl FA, Manninger M, Wunsch S, etal. Post-cardiac
injury syndrome triggered by radiofrequency ablation
for AVNRT.BMC Cardiovasc Disord. 2021;21:611.
https://doi.org/10.1186/s12872- 021- 02436- 1.
Further Reading
Dick M.Clinical cardiac electrophysiology in the young.
2nd ed. NewYork: Springer; 2015.
Fogoros RN, Mandrola JM.Fogoros’ electrophysiologic
testing. 6th ed. Wiley; 2018.
Steinberg JS, Mittal S.Electrophysiology, the basics. A
companion guide for the cardiology fellow during the
EP rotation. Philadelphia, PA: Lippincott, Williams,
and WIlkins; 2010.
Introduction toElectrophysiology
https://t.me/medicina_free
Devices
JamieA.Dietrich
13
Basics ofPacemakers
The components of a permanent pacemaker are
the pulse generator on the chest and the leads.
The leads are insulated wires that deliver electrical impulses from the generator to the myocardium and can sense cardiac depolarization. The
leads are most commonly transvenous, which
means they go through the vein to the cardiac
chambers. Leads are usually placed through the
subclavian vein. Leads can be placed in the right
atrium, right ventricle, or the epicardial surface
of the left ventricle via the coronary sinus. In the
right ventricle, leads can be placed in the RV
myocardium or targeted to the conduction system. In the latter setting, leads are positioned at
either the His bundle or deeply embedded in the
interventricular septum to engage the left bundle
with a goal of engaging the conduction system to
generate more physiologic pacing. When there is
a right and left ventricular lead in place, the
device is referred to as a biventricular or cardiac
resynchronization therapy (CRT) device. A
CRT-P is a biventricular pacemaker, and a CRT-D
is a biventricular pacemaker with debrillator.
When patients frequently pace in the right ventricle, it can result in loss synchrony between the
left and right ventricles and result in worsening
J. A. Dietrich (*)
Atrium Health Wake Forest Baptist,
Winston-Salem, NC, USA
e-mail: jadietri@wakehealth.edu
left ventricular function and clinical heart failure.
In fact, RV apical pacing produces a LBBB on
EKG.This is especially important since patients
with left bundle branch block and QRS duration
of >150 ms with HFrEF have indication for
CRT.Leads can also be placed on the epicardium
surgically if pacing is indicated and there is dif-
culty anatomically accessing the appropriate
cardiac chambers.
Leadless pacemakers are a newer type of
pacemakers which are placed into the right ventricle. These devices only provide single chamber
pacing support with some capability to track and
pace according to atrial activity. These are typically indicated in patients with permanent atrial
brillation, tachycardia bradycardia syndrome
with low pacing requirements or patients with
intermittent heart block with limited life expectancy. These devices can also be considered in
patients who have higher than normal infectious
risks or recurrent device infections [1]. Clinical
trials are now ongoing with dual chamber leadless pacing systems Fig.13.1.
Sensing is the term used to describe the detection of electrical activity in a particular cardiac
chamber. The leads detect the depolarization of
the local myocardium where they are implanted
and transmit this data to the pulse generator. The
magnitude of the signal is measured in millivolts
(mV). Sensitivity is a device setting dening the
threshold, in mV, at which the device will recognize that depolarization of the cardiac chamber in
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023
R. Musialowski, K. Allshouse (eds.), Cardiovascular Manual for the Advanced Practice Provider,
https://doi.org/10.1007/978-3-031-35819-7_13
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J. A. Dietrich
which the lead is positioned has occurred. For
example, suppose for a lead in the right atrium
that during atrial depolarization, a signal measuring 2 mV is measured. If the sensitivity of the
device is 1mV, the device will recognize that the
atrium has depolarized; if set to 3mV, it will not.
If the pacemaker senses the atrial or ventricular depolarization it was looking for, then it will
not pace (inhibit). If it does not sense the atrial or
ventricular depolarization it was looking for, then
it will pace the heart. A common analogy used to
describe the sensitivity settings is that of a fence.
If a tall fence or higher sensitivity setting is in
place, the pacemaker cannot see a lot of electrical
activity over the fence, so it is less sensitive. If a
short fence or low sensitivity setting is in place,
the pacemaker can see electrical impulses over
the fence, so it is more sensitive. Oversensing
leads to under pacing; undersensing leads to
overpacing [2].
The pacing threshold is the minimum amount
of energy, measured in voltage delivered over
time, needed to depolarize enough local myocardium to drive full depolarization of the cardiac
chamber. The parameters above are determined
at the time of pacemaker implant and are monitored over time [2]. They can sometimes vary in
the setting of certain medications or marked metabolic derangements [2].
The current is dened as the electricity ow,
which can be in either direction from the heart to
the pacemaker or from the pacemaker to the
heart. Impedance is anything that opposes the
normal ow of current. Ohm’s law is dened as
voltage (V) = current (I) × resistance (R)
Resistance is another term for impedance. This is
a measurement by the device to track the functionality. If there are abnormalities in the impedance, it usually indicates a problem with the leads
(either lead fracture or insulation break).
The pacemaker code consists of four letters
which conveys the mode in which the pacemaker
is operating. The letters describe in order the
chamber paced, chamber sensed, function, or
pacing response to a sensed beat and rate responsiveness. This code is used when describing single and dual chamber pacemakers (see
Table13.1).
For example, the most common type of pacemaker setting is DDDR. This means that the
pacemaker can pace in both the right atrium and
right ventricle, sense the intrinsic electrical activity in both chambers, track the atrial activity with
inhibition of ventricular pacing, and pacing that
is rate adaptive. VVI is another common setting
that might be seen with patients in permanent
Fig. 13.1 Leadless pacemaker is seen within the heart.
No evidence of pacemaker pulse generator or traditional
leads are seen on the CXR
atrial brillation who need pacing support. This
means that the pacemaker will pace in the right
ventricle, sense in the right ventricle, and then
not deliver a stimulus if intrinsic beat is sensed in
Table 13.1 Pacemaker code [3]
Chamber paced Chamber sensed Function Rate responsive
O=none O=none O=none O=none
A=atrium A=atrium I=inhibition R=rate adaptive
V=ventricle V=ventricle T=tracking
D=dual D=dual D=dual
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133
the ventricle. If the patient will remain in atrial
brillation, there is no need to provide pacing
support to the atrium. The mode depends on the
indication for which the pacemaker is placed. In
a patient with sinus node dysfunction who has a
problem with conduction in the right atrium, it
would be reasonable to program AAI or AAIR
but it is more common in the United States to
place a dual chamber device and program
DDD.In a patient with problems through the AV
node, the mode is typically DDD or DDDR.Rate
responsiveness means that the pacemaker can
increase the heart rate during exertion to meet the
metabolic demands of the body. Pacemakers typically have an accelerometer in the generator
which can sense movement and respond with
increase in heart rate. Application of a magnet to
a pacemaker results in asynchronous pacing
modes, AOO, VOO, or DOO meaning the device
does not sense intrinsic impulses [3].
Another important function of dual chamber
pacemakers is the ability for mode switching.
Tracking is a normal pacemaker behavior where
the device senses activity in one chamber (atrium)
and then delivers a stimulus in another chamber
(ventricle). The reason for mode switching is that
one would not want to pace the ventricle at the
atrial rate during atrial brillation or utter,
which could be as high as 300 bpm [3]. This
means that if the atrial rate is high as occurs in
atrial brillation or atrial utter, the pacemaker
will automatically switch to a mode where it does
not track.
Temporary Pacemakers
There are several types of temporary pacemakers
including transcutaneous pacing and temporary
transvenous pacemakers.
Transcutaneous pacing is using external pacing pads as well as an external cardiac monitor/
debrillator to pace the patient. The indication
for transcutaneous pacing is in patients with
second- or third-degree heart block with hemodynamic compromise refractory to medical
therapy such as atropine or dopamine until the
bradyarrhythmia resolves or a transvenous tem-
porary or permanent pacemaker can be placed.
It can be uncomfortable for the patient, and
sedation is typically required. It also can be limited by high capture thresholds since the pacemaker is external. Once the pacing pads have
been applied to the patient, the heart rate should
be set at 60–80bpm. Energy output in a temporary pacemaker is measured in current (mA)
rather than voltage. Typically, output should be
programmed at 10mA and then turned up until
capture is achieved, which is usually
50–100 mA. Capture is always veried by
assessing the pulse of the patient, not only looking at the monitors.
Transvenous pacing is using a temporary
pacemaker wire placed through either the internal jugular or femoral vein and then into the right
ventricle to provide pacing support. This can be a
oating temporary pacing wire, sometimes with a
balloon at the tip for stability, or an active xation
lead with a helix that can be used to xate the
lead into the myocardium. The patient is also
bedbound in this case with limited mobility.
Complications such as infection or lead migration (perforation) arise more frequently if these
are left in place for longer than 48h.
Indications forPacemakers
Current class I recommendations for pacemakers
include:
1. Symptomatic sinus node dysfunction that
leads to symptomatic bradycardia. This is the
most common indication for pacemaker
placement. This indication also includes
patient with tachycardia-bradycardia syndrome and chronotropic incompetence.
2. Second-degree Mobitz type II atrioventricular
(AV) block with symptoms, with wide QRS
escape or with block during exercise without
ischemia present.
3. Complete heart block/advanced second-
degree HB with symptoms, pauses >3 s,
escape <40bpm, wide escape, ablation of AV
node, AF with brady and pauses >5s while
awake.
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J. A. Dietrich
4. Fascicular block with intermittent CHB with
symptoms or second degree with or without
symptoms.
It is important to remember that the above are
indications for permanent pacemakers regardless
of symptoms and not attributable to reversible or
physiologic causes. If patients develop symptomatic AV block because of GDMT for which there
is not alternative treatment, permanent pacing is
also recommended [4].
Another important patient population to keep
in mind are those patients with neuromuscular
diseases associated with conduction disorders.
These include myotonic dystrophy or KearnsSayre syndrome. These patients may develop
second- or third-degree AV block. In the presence of these blocks or if the His bundle to ventricular myocardium time is greater than 70ms
(noted on intracardiac electrograms during EP
study), then permanent pacemaker is indicated
with debrillator capability if needed and meaningful survival of greater than 1year is expected
[4].
for the events should appear on the following
pages.
4. Lead impedance: An abrupt or greater than
30% change in lead impedance can signal a
lead fracture or insulation break.
5. Atrial arrhythmia burden or mode switches:
Some devices will report AT/AF burden in
terms of percentage. You can also get information about how many episodes of mode
switching occurred. This can give you important diagnostic information about atrial brillation burden.
6. Pacing percentages: If a patient is pacing
more than 40% in the right ventricle (LBBB),
this could lead to a pacemaker-induced cardiomyopathy due to loss of synchrony
between the ventricles. An echocardiogram
would be the next step to assess, especially if
the patient is symptomatic or the pacing percentages have increased from prior device
reports. In patients with LVEF <50% and high
burden of ventricular pacing, upgrade to
biventricular pacing (CRT-P) can be
considered.
Interpreting Device Interrogations
There are several important data points to review
with each device interrogation. The device
reports will have varying formats depending on
the manufacturer, but most of the important
information will be on the rst page of the report.
Six key things to note are:
1. Battery life (estimated in years): If a device
has reached elective replacement interval or
ERI, it is approaching time for a generator
change. Typically, the devices have 3months
from the date of ERI to safely replace the battery without compromising the device
function.
2. Settings: The pacemaker code will be put on
this, and it is important to know if it is DDDR,
VVIR, etc.
3. Events: If any high atrial rates, ventricular
rates or mode switches have occurred, these
will be contained in this summary. The EGMs
Implantable Cardioverter
Debrillators (ICDs)
Basic Principles ofDebrillators
An ICD can both pace and debrillate the heart.
The pacemaker functions apply to the ICD as
well. In addition, the ICD technology can recognize lethal arrhythmias such as ventricular tachycardia (VT) and ventricular brillation (VF). The
device can either pace the patient out of the
rhythm (for ventricular tachycardia) or deliver
synchronized or unsynchronized shocks. This
pacing is called antitachycardia pacing or ATP.
The ICD uses the heart rate to decide if a
rhythm should be treated. The settings are called
“zones.” Different zones can be used for VT and
VF. Commonly, patients who are on an antiarrhythmic such as amiodarone can have a slower
VT, so it can be necessary to make the zone lower
in order to sense the VT and treat it appropriately
[5]. Modern ICDs also have algorithms to try to
13 Introduction toElectrophysiology Devices
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recognize SVT and avoid shock delivery. These
algorithms are based on the morphology of the
signal detected in reference to regular rhythm,
relationship of atrial and ventricular activity, and
characteristics at onset of the rapid rhythm.
It is important to remember that an ICD can
provide therapy inappropriately for a tachycardia. This can occur when a patient has atrial
brillation with rapid ventricular response among
other SVTs. Reviewing a device interrogation
and EGMs for a patient with a shock is important
to ensure that the shock was appropriate [5].
Institutions have various shock protocols if a
patient receives an ICD shock. If a patient
receives one shock, it is important to review
device interrogation as well as to ask about symptoms that could have precipitated the shock
including ischemia or worsening heart failure.
Typically, the patient does not need to come to
clinic or the emergency room for this. If multiple
shocks are delivered in a short period of time, the
patient should go to the closest emergency room.
VT storm is dened as three or more ICD shocks
in a 24h period and is a medical emergency [5].
135
Fig. 13.2 Dual chamber ICD with a lead in the RV and
one in the RA
Temporary Debrillators
There are temporary debrillators called wearable cardioverter debrillator (WCD). WCD is a
class IIb recommendation after acute myocardial
infarction in patients with an LVEF of less than
or equal to 35%. It may be used if a patient has an
infection necessitating removal of a device as a
stop gap measure until a new device can be placed
[5].
Permanent Debrillators
ICDs can be single chamber with one lead in the
right ventricle, dual chamber with one lead in the
right atrium and one in the right ventricle (see
Fig.13.2) or biventricular (Fig.13.3). A CRT-D
is an ICD with one lead in the right ventricle and
one lead in the left ventricle via the coronary
Fig. 13.3 Biventricular ICD with a wire in the RV, RA,
and a LV lead at the 5 o’clock position
sinus. Subcutaneous ICDs are devices that are
implanted in the upper left abdominal area and
have no part of the device in the vasculature [5].
Subcutaneous ICDs are devices that are implanted
in the left axillary region with a lead that courses
from there to the parasternal region (Fig.13.4).
These devices are fully extravascular and offer
the advantage of reduced infection risk, avoiding
vascular compromise and comfort in some
patients. It is not capable of pacing.
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Fig. 13.4 Sub-cutaneous ICD generator in place on left
lateral chest with lead running along the sternum tunneled
under the skin
Indications forDebrillators
Primary prevention ICD means that the patient
has not had sustained VT or cardiac arrest.
Secondary prevention means that the patient has
had sustained VT or cardiac arrest. Sustained VT
is dened as at least 30s of VT [5].
Class I indications for ICDs include:
1. For primary prevention in patients with isch-
emic heart disease who are greater than
40 days from MI and/or more than 90 days
from revascularization despite maximally tolerated GMDT with an EF≤35% with at least
class II NYHA symptoms or with an
EF ≤ 30% with NYHA class I symptoms.
Patients need to have a life expectancy of
greater than 1year.
2. For secondary prevention in patients with
ischemic heart disease regardless of LVEF or
have syncope thought to be cardiac in etiology with LVEF less or equal to 35%. Patients
need to have life expectancy of greater than
1year.
3. For primary prevention in patients with non-
ischemic cardiomyopathy with HF NYHA
class II-III symptoms and LVEF less than or
equal to 35% despite maximally tolerated
GDMT.Patients need to have life expectancy
of greater than 1year.
J. A. Dietrich
4. For secondary prevention in patients with
nonischemic cardiomyopathy if they have had
sudden cardiac arrest or sustained VT [5].
Patients with hypertrophic cardiomyopathy
have increased risk of sudden death. There are
numerous risk factors, risk modiers, as well as
high risk substrates. Risk stratication should be
performed every 1–3 years in these patients to
determine the need for an ICD [5]. Indications
for subcutaneous debrillators are typically
patients without any need for a pacemaker function or in patients with high infectious risk or
recurrent device infections. Many young patients
with hypertrophic cardiomyopathy receive subcutaneous debrillators if indicated as the
patients are younger and likely to live longer than
a transvenous system would last [6]. Other indications for subcutaneous debrillators include
having cardiac anatomy that is difcult to access
or in patients with active lifestyles.
Interpreting Device Interrogations
The same principles as with pacemaker interrogations apply here. The important differences
include any tachycardia events, ICD therapies
which include antitachycardia pacing (ATP) or
shocks. The EGMs on the device interrogation
are important to review as well to get a sense if
the shock was appropriate or not.
Common Problems
andTroubleshooting Pacemakers
andICDs
Cardiac device manufacturers provide a great
deal of support for devices. It is important to
remember that a call can be placed to the cardiac
device company for an interrogation or troubleshooting. Often, the representatives can assist in
programming changes. Most device clinics also
employ cardiac device technicians to check and
monitor devices in the clinic. These individuals
can be invaluable in terms of knowledge and
troubleshooting devices.
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