S Afr Fam Pract
ISSN 2078-6190 EISSN 2078-6204

NW REFRESHER COURSE

Summary

PMs and ICDs are cardiac implantable electronic devices
(CIEDs) that are becoming increasingly sophisticated and the
perioperative management of these devices is changing along
with this development. Traditionally, PM functions have been
changed to asynchronous modes during surgery because of
the fear of electromagnetic interference (EMI) from diathermy
causing oversensing and subsequent loss of pacing. ICDs have
been switched to off mode to prevent inadvertent shocks during
EMI. This may lead to patient harm, due to R-on-T phenomenon
in PM set in asynchronous mode and undiagnosed perioperative
v-tach or v-fib in patients who have ICDs in off mode. PM-on and
ICD-on strategies are becoming more acceptable, depending
on the site of surgery. Intraoperative magnet use is currently
underutilised and may have advantages to changing PM and
ICD settings in patients who may otherwise have had the CIED
functions switched off. Reversal of functions to preoperative
settings may be achieved in the operating theatre without the
need of a PM technologist.

Background

Approximately 7500 PMs and ICDs are implanted every year into
patients in South Africa. Discovery Medical Aid submissions for
PMs and ICDs number 7200 per year, but this figure includes
new devices, temporary pacemaker insertion, generator
replacement for end of service (EOS) or end of life (EOL) and lead
changes or repositioning (see Figure 1).1,2 With patient longevity
rates increasing, it is becoming more likely that anaesthetists
will encounter patients with PMs and ICDs, especially in the
elderly. The medical technologists who specialise in CIEDs
provide an important service in interrogating these devices and
anaesthetists need to work closely with them in providing the
optimum perioperative care when patients with devices present
for surgery. All patients presenting for surgery need a recent
interrogation of their device and the information presented
to the surgical team. The anaesthetist should make decisions
regarding pacemaker management in conjunction with the
technologist, cardiologist and surgeon (see Figure 4).

Modern PMs and ICDs

PM technology was developed 60 years ago and recent
advances, especially over the last 10 years have taken a relatively

crude device that initially provided an asynchronous pacing
beat to the right ventricle as a life saving procedure for patients
with complete heart block to the sophisticated modern device
that paces on demand, reacts to exercise by increasing the
heart rate to a pre-set level and in the operating environment
can distinguish between a sensed beat and EMI. Many of the
guidelines for the management of PMs and ICDs were published
at the beginning of the current decade and could do with a
complete revision, taking into account the developments of
these devices over the last 10 years.

Perioperative considerations

PMs The anaesthetist has to weigh up the pros and cons of
either leaving a PM with its usual settings (PM-on) or asking
the technologist to change the settings to asynchronous mode
(either DOO or VOO). The problem that may be experienced with
a PM left in DDD mode is oversensing due to electromagnetic
interference (EMI) when the PM senses the EMI as electrical
activity of the heart and inhibits the generation of a paced
beat. This may result in periods of asystole while diathermy is
being used. Modern PMs have algorithms that can distinguish
between EMI and normal electrical activity in the heart and
may ignore diathermy induced EMI completely or change
the PM setting temporarily to DOO. The problem of a PM
changed to asynchronous mode is that an R-on-T phenomenon
may occur, which may result in ventricular fibrillation if an
asynchronous beat is delivered during the refractory period
of the cardiac cycle. The benefits of a PM-on protocol are that
the chances of an undiagnosed R-on-T phenomenon occurring
perioperatively are reduced and in addition, that the PM settings
do not have to be reset by a technologist postoperatively. If
the anaesthetist is planning to follow a PM-on protocol, the
preoperative interrogation should include the PM response
to magnet application as well as the ability to apply a magnet
intraoperatively to manage oversensing if it occurs due to EMI
(see Figure 7).

Many pacemakers are implanted today for disease of the
sinu-atrial node (Sick sinus syndrome - SSS) where the patient
experiences syncope due to bradycardia associated with SSS.
These patients have normal atrioventricular conduction and the
PM is set on AAI. Changing the PM to DOO or VOO may result
in asynchronous ventricular contraction because the ventricular

South African Family Practice 2019; 61(2):S4-S8

Open Access article distributed under the terms of the
Creative Commons License [CC BY-NC-ND 4.0]
http://creativecommons.org/licenses/by-nc-nd/4.0

Perioperative Management of Pacemakers (PM) and Implantable Cardioverter
Defibrillators (ICD) in South Africa
Keene A

Private Practice, Johannesburg
Corresponding author, email: tandpkeene@mweb.co.za

Perioperative Management of Pacemakers (PM) and Implantable Cardioverter Defibrillators (ICD) in South Africa 5

lead is usually placed in the right ventricle. The left ventricular
conduction and contraction is delayed and this may result in
reduced left ventricular efficiency. These patients would benefit
from a PM-on protocol.

ICDs are potentially problematic in that an ICD-on protocol
may result in unwanted and repeated shocks due to EMI being
misinterpreted by the device as ventricular fibrillation. This can
lead to myocardial damage and depletion of battery life. It has
been shown that ICDs do not respond to EMI if the operation site
is below the iliac crest and that the diathermy dispersive pad is
placed at a site to lead current away from the ICD.3 If an ICD-on
protocol is to be used, the anaesthetist should be aware of the
response to application of a magnet to the specific device (see
Figure 8).

An ICD-off protocol may result in undiagnosed v-tach or
v-fib in the perioperative period and case reports have been
published where patients have died at home after the
device was not checked and turned on postoperatively.
International literature is clear that the responsibility for
resetting the ICD belongs to the anaesthetist and not
to the technologist.4 An ICD-off protocol may result in
unnecessary external cardioversion for v-tach because
anti-tachy pacing (ATP) is disabled. ATP reduces the
need for shocks in patients who develop v-tach as many
tachyarrhythmias can be terminated by the rapid pacing
before the device has to deliver a shock (see Figure 3).

The standardised pacemaker codes are depicted in
Figure 2.5 Multisite ventricular pacing refers to cardiac
resynchronisation therapy (CRT) for the left and right
ventricles. It is utilised in patients with left bundle
branch block to resynchronise left and right ventricular
contraction to occur simultaneously. This may improve
cardiac output by up to 15% in patients with heart failure
due to reduced ejection fraction. Multisite atrial pacing is
used experimentally to treat atrial fibrillation.6

Implantable Cardioverter Defibrillator (ICD) and
Anti-Tachycardia Pacing (ATP)

Patients with recurrent ventricular tachycardia and/or ventricular

fibrillation or those at risk for developing these arrhythmias may

have an implantable cardioverter defibrillator (ICD) placed in the

left subclavian region. The ICD senses the R-R interval and if the

interval reduces to a predetermined level, the device algorithm

reads this as ventricular tachycardia and can deliver a repetitive

sequence of eight rapid paced beats to try to break the re-entry

condition of v-tach. If this fails to cardiovert the v-tach, a high

voltage shock is delivered (see Figure 3). The shock is delivered

from the coils to the generator in a triangulated vector to

incorporate the left ventricle. (The high voltage coils around the

pacemaker leads act as the cathode and the pulse generator

acts as the anode). ICDs recognise supraventricular tachycardias

(SVTs, AF and sinus tachycardia) via atrial sensing, but cannot

cardiovert them. This is designed to prevent unnecessary shocks.

ICDs may deliver anti-bradycardia therapy if required to do

so.7 A magnet applied to an ICD will generally disable the anti-

tachycardia therapy while it is in situ, but will have no effect on

anti-bradycardia therapy or rate responsiveness.

Figure 1: Implantation rate estimated to be 138.25/million in 2016 (total
population 54146735, total number 7485) US rates are double Germany

Figure 2: Pacemaker Codes

Figure 3: De-Identified printout from a patient’s ICD showing an episode of V-Tach
with attempted anti-tachy pacing (ATP) followed by successful 34.5 J defibrillation.
Image supplied by Medtronic SA.

S Afr Fam Pract 2019;61(2)6

Preoperative pacemaker interrogation is considered to be the

standard of care and should be scheduled during the week prior

to surgery. The PM technologist should provide the information

as shown in Figure 4 and in consultation with the technologist

and cardiologist and taking into account the planned surgery,

the anaesthetist should decide on the perioperative PM

management (see Figure 7).

If a PM-on strategy is to be followed, it is vitally important that

the effects of magnet application and removal to the specific

PM are known. It may be advantageous to reset the base rate

of the pacemaker, even though a PM-on protocol is followed.

For example, a base rate of 60 may be increased to 70 or 80 if

haemodynamic challenges are expected, such as blood loss or

neuraxial anaesthesia.

If the PM settings are to be changed, this should be done on

the day of surgery and preferably reversed to the preoperative

settings as soon as possible after the ESU is no longer required.

If an ICD-on strategy is to be followed, it is important to note that

placing a magnet over the ICD will not change the underlying

PM function and this has to be changed independently of the

anti-tachyarrhythmia function. This should be considered in PM

dependent patients if the surgery is close to the ICD and/or leads.

CRT devices need to be checked within 3 months because the
coronary sinus leads have poorer contact compared to the right
ventricular leads and higher thresholds are accepted. This may
result in faster battery drain and thus reduce longevity.

Response to magnet application

The response to magnet application in Medtronic PM and
ICDs is shown in Figure 5. It is important to note that there is
no uniformity across the industry, and each manufacturer has
a different set of responses to magnet application. This makes
it imperative that the anaesthetist is aware of the specific
response of the patient’s device before applying a magnet. An
indication of the enormity of this issue, is that in the USA, there
are 1440 different types of device models across the different
manufacturers.7,8 Modern PM and ICDs respond in a determined
manner to magnet application, and many of the problems
associated with application have been dealt with. Examples
include resetting device programming under the influence
of a magnet and concurrent EMI, and switching off anti-tachy
functions in ICDs which do not return once the magnet is
removed. These problems do not occur in modern devices.

During surgery, magnet application needs to be carefully
monitored. This is easily done in the patient with a PM,
because magnet application will result in a fixed rate change,
which is specific to the manufacturer. For example, Medtronic
pacemakers change from the patient’s usual settings to a rate of
85 beats per minute while the magnet is applied. This rate is 65
if the battery life is shortened (EOL) and the generator needs to
be replaced (RRT). Therefore, as long as the heart rate is 85 bpm,
the anaesthetist can be reassured that the magnet is correctly
applied.

It is less clear in the case of ICDs. The Medtronic ICDs emit a tone
for 10 seconds when the magnet is applied, but after this initial
signal, there is no indicator to the anaesthetist whether or not
the magnet is still in place and exerting its effect on the ICD. The
magnet has no effect on the PM function of the ICD, so heart rate
changes cannot be used as an indicator. It would make sense for
the manufacturers to provide the anaesthetist with an ongoing
signal to determine correct placement of a magnet over an ICD.
Modern devices have Bluetooth functionality and an elegant

Patients with recurrent ventricular tachycardia and/or ventricular fibrillation or those at risk for
developing these arrhythmias may have an implantable cardioverter defibrillator (ICD) placed in
the left subclavian region. The ICD senses the R-R interval and if the interval reduces to a
predetermined level, the device algorithm reads this as ventricular tachycardia and can deliver a
repetitive sequence of eight rapid paced beats to try to break the re-entry condition of v-tach. If
this fails to cardiovert the v-tach, a high voltage shock is delivered (see Figure 3). The shock is
delivered from the coils to the generator in a triangulated vector to incorporate the left ventricle.
(The high voltage coils around the pacemaker leads act as the cathode and the pulse generator
acts as the anode). ICDs recognise supraventricular tachycardias (SVTs, AF and sinus
tachycardia) via atrial sensing, but cannot cardiovert them. This is designed to prevent
unnecessary shocks. ICDs may deliver anti-bradycardia therapy if required to do so.7 A magnet
applied to an ICD will generally disable the anti-tachycardia therapy while it is in situ, but will
have no effect on anti-bradycardia therapy or rate responsiveness.

Figure 4. Preoperative Pacemaker and ICD Interrogation

Preoperative pacemaker interrogation is considered to be the standard of care and should be
scheduled during the week prior to surgery. The PM technologist should provide the information
as shown in Figure 4 and in consultation with the technologist and cardiologist and taking into
account the planned surgery, the anaesthetist should decide on the perioperative PM
management (see Figure 7).
If a PM-on strategy is to be followed, it is vitally important that the effects of magnet application
and removal to the specific PM are known. It may be advantageous to reset the base rate of the
pacemaker, even though a PM-on protocol is followed. For example, a base rate of 60 may be
increased to 70 or 80 if haemodynamic challenges are expected, such as blood loss or neuraxial
anaesthesia.
If the PM settings are to be changed, this should be done on the day of surgery and preferably
reversed to the preoperative settings as soon as possible after the ESU is no longer required.
If an ICD-on strategy is to be followed, it is important to note that placing a magnet over the ICD
will not change the underlying PM function and this has to be changed independently of the anti-

Figure 5: Response to magnet application in Medtronic PM and ICDs

way off dealing with this problem would be to have a smartphone application that can read the
wireless signals from the device.

Figure 6: Operating Theatre Requirements

PM-on or CRT-P-on protocol suggests that the PM settings are not changed during the standard
preoperative technologist interrogation of the device. PM-on protocol will avoid inadvertent
development of R-on-T phenomenon and implies that magnet application is possible if the
situation of oversensing caused by EMI develops. In addition to this, the anaesthetist is able to
remove the magnet when EMI is no longer being used. It takes away the need for postoperative
high dependency unit care and a repeat call out by the technologist to reset the PM. The
successful PM-on protocol requires the anaesthetist to follow the algorithm in Figure 7. A magnet
can disable the rate responsiveness function in a PM and this is useful to prevent unwanted
increases in heart rate, for example when the sternal saw is used in open-heart procedures, as
the vibration of the saw may be misinterpreted as patient movement (see Figure 7).
ICD or CRT-D-on protocol suggests that the anti-tachycardia therapy of the ICD is not switched
off perioperatively and that the device is allowed to sense tachyarrhythmias and deliver anti-
tachycardia pacing (ATP) and shock if necessary. This provides protection to the patient in the
event of V-Tach and/or V-fib, which may occur at anytime perioperatively. In order to prevent
unnecessary ATP or shocks due to EMI being incorrectly read by the generator, a magnet should
be available to place over the ICD to change the setting to ATP and Shock off. It is important to
note that the anaesthetist should know exactly what happens to the specific ICD under the
influence of magnet application and removal, that the patient position is such that the magnet can
be properly secured during surgery and that the tone emitted by the generator is recognised.
There are certain operating sites where it is safe to leave the ICD on and generally these are more
that 15 cm (6 inches) from the generator and leads and below the umbilicus or ileac crest, as
long as the ESU dispersal pad is sited away from the surgical site so that EMI is not directed
towards the ICD.3 For example, hip surgery is safe to proceed without switching off the anti-tachy
therapy, as long as the dispersal pad is placed on the ipsilateral thigh.
The anaesthetist should consider switching off the anti-tachy therapy of the ICD if:

Figure 6: Operating Theatre Requirements

Figure 4. Preoperative Pacemaker and ICD Interrogation

Perioperative Management of Pacemakers (PM) and Implantable Cardioverter Defibrillators (ICD) in South Africa 7

way of dealing with this problem would be to have a smartphone
application that can read the wireless signals from the device.

ICD or CRT-D-on protocol suggests that the anti-tachycardia
therapy of the ICD is not switched off
perioperatively and that the device is allowed
to sense tachyarrhythmias and deliver anti-
tachycardia pacing (ATP) and shock if necessary.
This provides protection to the patient in the event
of V-Tach and/or V-fib, which may occur at anytime
perioperatively. In order to prevent unnecessary
ATP or shocks due to EMI being incorrectly read
by the generator, a magnet should be available to
place over the ICD to change the setting to ATP
and Shock off. It is important to note that the
anaesthetist should know exactly what happens
to the specific ICD under the influence of magnet
application and removal, that the patient position
is such that the magnet can be properly secured
during surgery and that the tone emitted by
the generator is recognised. There are certain
operating sites where it is safe to leave the ICD
on and generally these are more that 15 cm (6
inches) from the generator and leads and below
the umbilicus or ileac crest, as long as the ESU
dispersal pad is sited away from the surgical site
so that EMI is not directed towards the ICD.3 For
example, hip surgery is safe to proceed without
switching off the anti-tachy therapy, as long as
the dispersal pad is placed on the ipsilateral thigh.

The anaesthetist should consider switching off
the anti-tachy therapy of the ICD if:

1. The operation site is within 15 cm of the
generator or leads, especially if long bursts of
unipolar diathermy are to be used. The argon
beam ESU cannot be used in short bursts and
may cause long periods of EMI.

2. A magnet cannot be reliably secured over the
generator, such as in the prone position.

3. Certain operations such as hand surgery and
ophthalmic operations where inadvertent
shocks may lead to patient or operator harm.

This would include operations at these sites performed under

local anaesthesia. Thoracic operations would require the ICD-

off because left chest procedures would render the anti-tachy

functions ineffective because of poor tissue shock transfer due

to high impedance when the chest is open. Also, in right chest

procedures, it would be difficult to ensure proper application

and security of the magnet if it was required.9

If the patient is pacemaker dependent, the anaesthetist may

consider asking the PM tech to change the PM settings to

DOO as in the PM-on protocol. It is also advisable to turn off

rate responsiveness, as this function is not changed by magnet

application in ICDs.

It is important to note that if the anti-tachy function has been

turned off (ICD-off ), the settings must be restored as soon as

possible after the procedure and the patient has to be observed

in a high dependency unit until this has been achieved.

1. The operation site is within 15 cm of the generator or leads, especially if long bursts of
unipolar diathermy are to be used. The argon beam ESU cannot be used in short bursts
and may cause long periods of EMI.

2. A magnet cannot be reliably secured over the generator, such as in the prone position.
3. Certain operations such as hand surgery and ophthalmic operations where inadvertent

shocks may lead to patient or operator harm. This would include operations at these
sites performed under local anaesthesia. Thoracic operations would require the ICD-off
because left chest procedures would render the anti-tachy functions ineffective because
of poor tissue shock transfer due to high impedance when the chest is open. Also, in right
chest procedures, it would be difficult to ensure proper application and security of the
magnet if it was required.9

If the patient is pacemaker dependent, the anaesthetist may consider asking the PM tech to
change the PM settings to DOO as in the PM-on protocol. It is also advisable to turn off rate
responsiveness, as this function is not changed by magnet application in ICDs.
It is important to note that if the anti-tachy function has been turned off (ICD-off), the settings
must be restored as soon as possible after the procedure and the patient has to be observed in a
high dependency unit until this has been achieved.

Figure 7: PM-on algorithm

Figure 8: ICD-on algorithm

References

1. Personal communication Darren Sweiden, Discovery.
2. Bonny A, Ngantcha M, Jeilan M, Okello E, Kaviraj B, Talle MA, et al. Statistics on the use of

cardiac electronic devices and interventional electrophysiological procedures in Africa
from 2011 to 2016: report of the Pan African Society of Cardiology (PASCAR) Cardiac
Arrhythmias and Pacing Task Forces. Europace. 2017;00:1-14.

3. Gifford J, Larimer K, Thomas C, May P. ICD-ON Registry for Perioperative Management of
CIEDs: Most Require No Change. PACE. 2017;40:128-34.

4. Healey JS, Merchant R, Simpson C, Tang T, Beardsall M, Tung S, et al. Society Position
Statement: Canadian Cardiovascular Society/ Canadian Anesthesiologists’ Society/
Canadian Heart Rhythm Society joint position statement on the perioperative
management of patients with implanted pacemakers, defibrillators and
neurostimulating devices. Can J Anesth. 2012 Apr;59(4):394-407

5. Benson R. Pacemaker Nomenclature. St Louis Dept Anesthesia, 2005-2006. Available
from: http://anesthesia.slu.edu/pdf/pacemaker.pdf

6. Diprose P, Piece JM. Anaesthesia or patients with pacemakers and similar devices. BJA
CEPD Reviews. 2001 Dec 1;1(6):166-70.

7. Jacob S, Panaich SS, Maheshwari R, Haddad JW, Padanilam BJ, John SK. Clinical
applications of magnets on cardiac rhythm management devices, Europace.
2011:13(9):1222-30.

8. Schulman PM, Rozner MA. Use caution when applying magnets to pacemakers or
defibrillators for surgery. Anesth Analg. 2013;117:442-7.

9. Crossley GH, Poole JE, Rozner MA, Asirvatham SJ, Cheng A, Chung MK, et al. The Heart
Rhythm Society (HRS)/American Society of Anesthesiologists (ASA); Expert Consensus
Statement on the perioperative management o patients with implantable defibrillators,
pacemakers and arrhythmia monitors. Heart Rhythm. 2011 Jul;8(7):1114-54.

Glossary of terms, abbreviations and acronyms

Figure 7: PM-on algorithm

Figure 8: ICD-on algorithm

S Afr Fam Pract 2019;61(2)8

References
1. Personal communication Darren Sweiden, Discovery.

2. Bonny A, Ngantcha M, Jeilan M, Okello E, Kaviraj B, Talle MA, et al. Statistics on
the use of cardiac electronic devices and interventional electrophysiological
procedures in Africa from 2011 to 2016: report of the Pan African Society of
Cardiology (PASCAR) Cardiac Arrhythmias and Pacing Task Forces. Europace.
2017;00:1-14.

3. Gifford J, Larimer K, Thomas C, May P. ICD-ON Registry for Perioperative
Management of CIEDs: Most Require No Change. PACE. 2017;40:128-34.

4. Healey JS, Merchant R, Simpson C, Tang T, Beardsall M, Tung S, et
al. Society Position Statement: Canadian Cardiovascular Society/ Canadian
Anesthesiologists’ Society/ Canadian Heart Rhythm Society joint position
statement on the perioperative management of patients with implanted
pacemakers, defibrillators and neurostimulating devices. Can J Anesth. 2012
Apr;59(4):394-407

5. Benson R. Pacemaker Nomenclature. St Louis Dept Anesthesia, 2005-2006.
Available from: http://anesthesia.slu.edu/pdf/pacemaker.pdf

6. Diprose P, Piece JM. Anaesthesia or patients with pacemakers and similar
devices. BJA CEPD Reviews. 2001 Dec 1;1(6):166-70.

7. Jacob S, Panaich SS, Maheshwari R, Haddad JW, Padanilam BJ, John SK. Clinical
applications of magnets on cardiac rhythm management devices, Europace.
2011:13(9):1222-30.

8. Schulman PM, Rozner MA. Use caution when applying magnets to pacemakers
or defibrillators for surgery. Anesth Analg. 2013;117:442-7.

9. Crossley GH, Poole JE, Rozner MA, Asirvatham SJ, Cheng A, Chung MK, et al.
The Heart Rhythm Society (HRS)/American Society of Anesthesiologists (ASA);
Expert Consensus Statement on the perioperative management o patients with
implantable defibrillators, pacemakers and arrhythmia monitors. Heart Rhythm.
2011 Jul;8(7):1114-54.

Glossary of terms, abbreviations and acronyms

ATP – Anti Tachycardia Pacing

BOL –Beginning of Life

CIED – Cardiac Implantable Electronic Device

CRMD – Cardiac Rhythm Management Device

CRT – Cardiac Resynchronisation Therapy

EOL – End of Life

EOS – End of Service (same as RRT)

ESU – Electrosurgical Unit

ICD – Implantable Cardioverter Defibrillator

IPD – Implantable Pulse Generator

PM – Pacemaker

RRT – Recommended Replacement Time