Lancashire_and_South_Cumbria_Cardiac_physiologist_training_pacing_manual.pdf

Lancashire & South Cumbria
Cardiac Network
PACING MANUAL
Cardiac Physiologist Training Manual
D:PACING MANUAL.doc
04/01/2005 Created by ButlerL

THE PACEMAKER SYSTEM
AN OVERVIEW
• Normal Conduction
• Abnormal Conduction and the indications for pacing
• Pacemakers and the modes of pacing
• Ventricular pacing systems
• Atrial Pacing systems
• Dual chamber Pacing systems
• Implantation techniques and measurements
• End of Life Details
D:PACING MANUAL.doc

Normal Conduction
AV ring
SA Node
AV Node
Left Bundle
Branch
Right Bundle Branch
The impulse that is responsible for depolarisation of the heart is initiated by
the Sino-Atrial Node (SA Node), which is positioned in the top corner of the
right atrium, close to the SVC and atrial myocardial junction.
The impulse travels across the atria to form the P wave of the ECG. It is
thought that distinct muscle fibres assist in the spread of atrial depolarisation
across the atria.
The impulse reaches the Atrio-Ventricular Node (AV Node) at the junction of
the atria and ventricles within the atrial/ventricular septum. The only
passageway for the impulse in the normal heart is through the AV Node and
Bundle of His. This is due to the presence of the electrically isolated AV ring.
At the AV node there is a delay, which allows time for ventricular filling and
protects the ventricles from fast conducting atrial arrhythmias.
The impulse then travels down the left and right bundle branches. Further
divisions eventually form the purkinje fibres. These form an intricate network
of specialised conducting cells which spread throughout the myocardium. The
impulse initiates ventricular depolarisation (QRS complex). Repolarisation of
the ventricles then takes place (T wave).
D:PACING MANUAL.doc

Abnormal Conduction and Indications for pacing
Abnormal conduction – overview
The SA Node has the ability to discharge an impulse with no external
stimulation. It usually does so at a rate of approximately 80 beats per minute
(bpm), unless acted upon by the sympathetic / parasympathetic nervous
system or chemical substances e.g. adrenalin, nor adrenalin.
If the SA node fails, the AV node may be able to take over this function and
the intrinsic discharge rate is approximately 60 bpm. The Bundle of His has an
intrinsic discharge rate of 50 bpm and bundle branches of 40 bpm. The
purkinje fibres will discharge at 20 bpm.
If there are any abnormalities of the SA node or further down the conducting
system the rate may fall and pacing becomes necessary.
Indications for pacing
Group 1
Implantation is considered acceptable and necessary, provided that the
conditions are chronic or recurrent and not due to a transient cause.
1. Sinus Node Dysfunction
2. Congenital Complete Heart Block
3. Acquired Complete Heart Block
4. Symptomatic Mobitz type II, second degree heart block
5. Symptomatic Mobitz type I, second degree heart block
6. Symptomatic sinus bradycardia
D:PACING MANUAL.doc

Group 2
Implantation is considered acceptable and necessary, provided the medical
history and prognosis of the patient can be documented and there is evidence
that pacemaker implantation will assist in the overall management of the
patient
1. Bifascicular/trifascicular block accompanied by syncope
2. Asymptomatic Mobitz type I, second degree heart block
3. Symptomatic sinus bradycardia that is a consequence of long-term
drug treatment for which there is no acceptable alternative.
4. Patients with recurrent and refractory ventricular tachycardia
5. Atrial/ventricular arrhythmias
6. Heart failure
Group 3
Conditions listed below should be an indication in support to those given in
groups 1 and 2.
1. Syncope of undetermined cause
2. Sinus bradycardia without significant symptoms
3. Sino-Atrial block without significant symptoms
4. 1st
degree AV block, atrial fibrillation or other causes of transient
pauses
5. Bradycardia during sleep
6. Right Bundle Branch Block with LAD
D:PACING MANUAL.doc

Pacemakers And Modes Of Pacing
A pacemaker system consists of a pulse generator and lead. The pulse
generator has contained in its housing a power source and electronic circuitry
which enables proper pacemaker function. The lead is made up of a
conductor covered by insulation. At the proximal end is a terminal pin which
fits into the pulse generator snugly and makes the connection between lead
and generator. At the distal end is the electrode which makes contact with the
heart muscle. In unipolar systems, the pulse generator is the positive anode
and the electrode tip in the heart is the negative cathode.
Pacing – The USCI code
The USCI code is the standard code for labelling the mode of pacing.
1ST
letter – chamber(s) paced
2nd
letter – chamber(s) sensed
3rd
letter – Mode of action
Either the atria or ventricles can be paced and hence either pure atrial, pure
ventricular or both atrial and ventricular pacing can be employed. Therefore
modes of AAI, VVI, VVT, VAT, DDI, DDD and others may be chosen. The
mode of action is either inhibited (I), where the pacemaker will suppress its
output if an intrinsic beat is seen or triggered (T), where the output of a
pacemaker is triggered to a sensed event.
The triggered mode is used in normal DDD function or to prevent undesirable
inhibition e.g. oversensing of skeletal muscle activity.
D:PACING MANUAL.doc

Ventricular Pacing Systems
VOO – Ventricular Asynchronous
In this mode the pacemaker stimulates at a fixed rate and voltage. There is no
sensing and hence the pacemaker will continue to pace irrespective of the
underlying rhythm. The pacemaker will capture the heart if the impulse
delivered falls outside the refractory period of the intrinsic beat.
This mode can also be seen with application of magnet on most pacemaker
models.
VVI – Ventricular Inhibited
This is by far the most common of ventricular only pacing modes.
Spontaneous impulses are sensed and the subsequent output is stopped. If
no spontaneous impulses occur the pacemaker will pace at the regular rate at
which the pacemaker is set.
D:PACING MANUAL.doc

VVT- Ventricular Triggered
In this mode when a spontaneous ventricular intrinsic beat is seen the output
of the pacemaker is delivered. It must be noted that the beat will not be fully
captured by the pacemaker as the output delivered will fall in the refractory
period of the intrinsic beat and make no contribution to the depolarisation of
the heart (this is called a pseudo-fusion beat).
D:PACING MANUAL.doc

Atrial Pacing Systems
AOO – Atrial Asynchronous
This mode is rarely used. As in VOO, the pacemaker stimulates at a fixed rate
irrespective of the underlying rhythm.
This mode can also be seen on application of a magnet on most pacemaker
models.
AAI – Atrial Inhibited
This mode is the same as the VVI mode except the lead is positioned next to
atrial myocardium and therefore the pacemaker will inhibit when an intrinsic
atrial beat is seen.
D:PACING MANUAL.doc

AAT – Atrial Triggered
In this mode when a spontaneous atrial intrinsic beat is seen the output of the
pacemaker is delivered. It must be noted that the beat will not be fully
captured by the pacemaker as the output delivered will fall in the refractory
period of the intrinsic beat and make no contribution to the depolarisation of
the heart (this is called a pseudo-fusion beat).
D:PACING MANUAL.doc

Dual Chamber Pacing Systems
DOO – AV Synchronous
The ‘D’ in the USCI code stands for dual, meaning atria and ventricle. In this
instance, both chambers are paced at a fixed rate with no sensing,
irrespective of the underlying rhythm. This mode is rarely used and can be
seen with application of a magnet on most DDD pacemaker models.
Atrial Synchronous (VAT)
This mode occurs when the atrial intrinsic rate is sensed and the ventricular
chamber is paced. The pacemaker output is triggered to a sensed event, that
event being a sinus P wave. In this way AV synchrony is maintained and the
response will be physiological because it will follow the intrinsic rate of the
sinus node.
D:PACING MANUAL.doc

Fully Automatic
The pacemaker has the ability to:
1. Sense and pace the atrium
2. Sense and pace the ventricle
3. Inhibit atrial and ventricular intrinsic beats
4. Trigger a paced event to a sensed event (VAT)
In this mode there will always be AV Synchrony, whether sinus, Atrial pacing,
VAT pacing or AV pacing occurs.
With sinus and VAT pacing there will also be a physiological response to
exercise due to the increase in sinus rate of the patient.
Chronotropic competence – the sinus rate will increase in response to
exercise, emotion etc.
Chronotropic incompetence – the sinus rate will not increase in response to
exercise, emotion etc.
For the dual chamber DDD mode to be effective chronotropic competence
must be present.
D:PACING MANUAL.doc

Implantation Techniques and Measurements
Implantation Techniques
The routine placement of pacemaker leads involves placing the atrial lead
(electrode) in the right atrial appendage and the ventricular lead in the right
ventricular apex.
The route used is the subclavian or cephalic vein. Either the ‘stab’ technique
(inserting a needle until the subclavian vein is found) or a ‘cut down’ technique
(separating superficial tissues until cephalic vein is found) is employed.
A stylet is introduced into the lead to give stiffness to the electrode. The lead
is then passed down the vein into the desired position.
The atrial appendage is in a posterior and superior position and the atrial ‘J’
shaped lead is ‘hooked’ up into this region.
The right ventricle has undulations or trabeculae, its surface being rough
rather than a smooth wall lining. The tip of the electrode has small plastic
attachments called fins or tines. Their presence assists in the electrode
attaching to the trabeculae, aiding its fixture to the endocardial wall.
Fibrous tissue will eventually integrate itself into and around the tip of the
electrode, providing firm attachment of the lead.
Measurements can be carried out to confirm a good position of the lead, after
which the electrode can be firmly sutured into the vein to prevent movement
of the electrode. The pulse generator can then be attached to the lead. The
terminal pin of the lead is pushed into the connector head of the pulse
generator and to ensure electrical contact the connector head screw is
tightened.
A pocket is made in the pectoral muscle sheath to allow placement of the
pulse generator. The wound can then be closed and the area cleaned.
Measurements Taken At Implant.
D:PACING MANUAL.doc

Measurements are taken after lead positioning. This confirms an adequate
position and checks the stability of the lead.
1. Voltage Threshold
The least amount of energy required to depolarise the
myocardium.
2. Current flow
3. Lead impedance
4. Amplitude of intrinsic P/R wave
Asking the patient to cough, sniff and breathe deeply whilst pacing and
screening the heart tests the stability of the lead.
If all these measurements are satisfactory it indicates good placement of the
lead and good contact between electrode tip and myocardial interface.
End Of Life Details
The end of life or recommended replacement time of a pacemaker is
established by numerous methods. These include:
1. Magnet test
2. Battery status
3. Battery voltage measurement
4. Battery impedance measurement
Each model and manufacturer type of pacemaker has different EOL or RRT
characteristics. These can be established from the pacemaker manuals.
LJR.TPS.001.01
D:PACING MANUAL.doc

ECG INTERPRETATION
Normal methods of ECG interpretation cannot be applied to the ECG
recorded during pacing.
AAI PACING
The impulse is seen on the ECG as a spike (pacing artefact) followed by atrial
depolarisation – a paced ‘p’ wave.
The paced P will be abnormal in shape to that of a sinus p wave due to the
atria being depolarised from a different stimulus.
Paced Paced
P wave P wave
With AAI pacing it is important to have an intact conducting system from the
AV node onwards.
In this way AAI pacing gives synchronisation between atria and ventricles –
AV synchrony.
Intermittent SA arrest – AAI pacing.
Chronic SA arrest – AAIR pacing.
SA arrest + sinus bradycardia – AAIR pacing.
D:PACING MANUAL.doc

I.e. if chronotropic response is missing from the SA node then rate response
pacing is needed to give an increase in rate to exercise.
AAI SENSING
AAI pacing allows inhibition (mode of action) of any sensed intrinsic beats
arising from the atria.
Sensed intrinsic
P wave
After sensing an intrinsic P wave the pacemaker resets and waits the
programmed interval before emitting a further stimulus.
D:PACING MANUAL.doc

VVI PACING
The impulse is seen on the ECG as a spike (pacing artefact) followed by
ventricular depolarisation – a paced QRS complex.
The paced QRS is (1) abnormal in shape (bizarre)
(2) broad
(3) abnormal T wave
Paced Paced Paced
QRS QRS QRS
There is no synchronisation between the atria and ventricles and the sinus p
waves show no correlation to the QRS on the ECG.
QRS QRS QRS
P P P P P P
D:PACING MANUAL.doc

VVI SENSING
VVI pacing mode allows inhibition of any sensed intrinsic beats.
Mode of action – inhibited
After sensing an intrinsic QRS the pacemaker resets and waits the
programmed interval before emitting a further stimulus.
D:PACING MANUAL.doc

DDD
Chambers paced – Dual (ATRIA AND VENTRICLES)
Chambers sensed – Dual (ATRIA AND VENTRICLES)
Mode of action – Dual (INHIBITED AND TRIGGERED)
Sensed P wave - INHIBIT
Sensed QRS complex - INHIBIT
Paced P wave
Sensed QRS complex - INHIBIT
Sensed P wave - INHIBIT
Paced QRS complex - TRIGGERED
Paced P wave
Paced QRS complex
(AV sequential pacing)
D:PACING MANUAL.doc

FAILURE TO CAPTURE
Not enough energy is being delivered to cause depolarisation of the
myocardium (all or nothing phenomena).
E.g. VVI – Failure to capture
Intermittent failure to capture
FAILURE TO SENSE
No intrinsic cardiac activity is seen by the pacemaker and therefore continues
to output at the programmed interval.
E.g. VVI – failure to sense (UNDERSENSING)
LJR..PI001.
D:PACING MANUAL.doc

TECHNICAL MEASUREMENTS AT IMPLANT
ECG MONITORING
The lead usually chosen for pacemaker implants is limb lead II, however if all
limb leads are available, as many as possible should be used to monitor the
patient during the procedure. This holds the advantage of being able to see
clear pacing spikes, followed by depolarization of either atria or ventricular
myocardium. Particularly useful when looking for atrial capture.
Ventricular Axis
If the ventricular pacing electrode is positioned in the right ventricular apex, a
left Bundle Branch Block pattern is seen with a Left Axis Deviation or Superior
Axis. This is because depolarization begins at the site of activation, the apex
of the Right Ventricle. In LBBB, the spread of activation is first seen in the RV
and then spreads to the LV.
If the ventricular pacing electrode is positioned at the Right Ventricular
Outflow Tract (RVOT), a LBBB pattern is seen but this time with an inferior
axis or Right Axis Deviation.
If a right bundle branch pattern is seen, this may imply electrode position in
the LV, possibly through an existing VSD or even through a septal rupture.
Atrial Axis
The P wave Axis in normal sinus rhythm is the same as the QRS axis
(between -30º & +90º). Right Atrial Appendage (RAA) pacing will also give a
normal P wave axis. Septal pacing (usually posteroseptal) will give a superior
axis and would lead to inverted P waves in the inferior leads.
D:PACING MANUAL.doc

EQUIPMENT REQUIREMENTS
(A) NEW SYSTEM
A Pacing Systems Analyser (PSA) is used to provide pacing at varying
outputs and pulse durations for the purpose of taking electrode/pacing lead
measurements.
Lead connectors connect from the PSA to the pacing electrode(s)
positioned in the heart.
The positive (red) (anode) lead is the indifferent electrode and in a unipolar
system can be electrically connected to the body tissues by a spatula/spade
positioned in the pacemaker pocket.
The negative (black) (cathode) is the active lead and is connected to the lead
tip via the proximal end of the electrode.
In a bipolar system, the Positive (red) lead is connected to the ‘Ring’ electrode
represented at the proximal end of the electrode. The negative (black) lead is
connected to the proximal end of the electrode itself and like the unipolar
system takes measurements from the tip of the lead.
Introducers, pacing electrodes and pacemaker.
Ensure compatibility with introducer and lead diameter (French) size.
Ensure compatibility with pacing electrode and pacemaker connection size.
D:PACING MANUAL.doc

(B) PACEMAKER REPLACEMENT
Underlying rhythm should be assessed prior to the procedure and temporary
pacing cover provided if necessary.
Once the pacemaker is exposed a screwdriver is needed to release the
electrode from the pacemaker.
The lead is checked in the normal manner. For leads in situ long term, higher
thresholds (up to 2.0v) may be accepted provided it is consistent with recent
pacemaker checks. The new pacemaker can then be connected in the normal
manner.
If the new pacemaker has an incompatible connector size to the lead in situ
then the old lead may need to be adapted. Pacemaker lead adaption should
be avoided by the correct choice of pacemaker size. The risks of adapting a
pacemaker lead include electrode damage and loose connection.
Method of Adaption
The electrode is cut using wire cutters and the insulation cut back slightly to
expose the wire.
The bare wire is placed into the adaptor and according to design is crimped or
screwed into place using crimpers or small screwdriver.
The insulation of the adaptor is moved over the bare wire and measurements
of the lead rechecked.
Particular attention should be paid to check lead impedances and for pectoral
muscle stimulation that would indicate a gap in insulation between lead and
adaptor.
D:PACING MANUAL.doc

ELECTRODE MEASUREMENTS
Once the electrode has been positioned various electrical
measurements are taken to check electrode placement and stability.
These measurements are:
(a) Stimulation voltage threshold
(b) Current
(c) Impedance
(d) Sensing Threshold, P/R wave amplitude
(e) Slew Rate
(f) Intracardiac ECG
PULSE DURATION – the actual duration (time) of the pacemaker stimulus
measured in milliseconds (ms). The pulse duration is usually set to 0.5ms and
the stimulation, voltage threshold is measured at this setting.
Voltage
(V)
Pulse
Duration
(ms)
D:PACING MANUAL.doc

STIMULATION THRESHOLD
This is the minimum output required to stimulate the heart. The pulse
duration of the pacemaker stimulus should be set to 0.5ms. The voltage
output is decreased until it fails to capture the heart. i.e. fails to provide
enough energy to cause contraction of the atria or ventricles. The stimulation
threshold is 0.1V above the point at which loss of capture is seen.
The output/stimulation threshold is measured in volts (V).
LOC LOC
LOC – loss of capture
The stimulation threshold should be below 1 volt to ensure satisfactory
placement of the electrode.
CURRENT
The delivered current at voltage threshold is then measured. This figure is
derived from the threshold voltage and the measured impedance (V=IxR). The
voltage and current have an exponential relationship.
The current is measured in milliamps (ma).
D:PACING MANUAL.doc

IMPEDANCE
The impedance is a measure of resistance to current flow down the electrode.
It is a result of the sum of the electrical resistance of the wire, the electrode
tip/myocardial interface and the impedance of the return circuit to the
pacemaker (the body and blood pool). The impedance should be measured at
stimulation threshold and is used to check for lead or insulation break.
A normal impedance is usually between 400 – 1000 Ohms (Ω)
A low impedance < 400 Ohms may indicate current leakage caused by a
break in insulation.
A high impedance > 1000 Ohms may indicate a resistance to current flow and
may be due to a fracture of the electrode or poor electrode/pacemaker
connection.
Stability of this measurement is important and the lead impedances today
appear to be higher than previous. If all other measurements are satisfactory
‘borderline’ impedance measurements can be accepted. Available are ‘high
impedance’ electrodes which will produce high impedance measurements up
to 2500 Ohms. High Impedance electrodes aim to reduce current flow and
lead to increased longevity.
Impedance is measured in Ohms (Ω).
SENSING THRESHOLD / INTRINSIC AMPLITUDE
The amplitude of the P or R wave must be measured to ensure the
pacemaker will adequately sense the intrinsic rhythm if present from both the
atrial and ventricular chambers independently.
The P wave amplitude should be > 3mv
The R wave amplitude should be > 5mv
Any measured P/R waves smaller than these values may lead to
undersensing.
Intrinsic amplitudes are measured in Millivolts (mv)
D:PACING MANUAL.doc

SLEW RATE
This is the measure of the slope of the upstroke (dV/dt) of the sensed P/R
waves. A large slew rate helps the pacemaker to correctly identify sensed
events and so appropriately ignore other sensed events (T waves and muscle
activity).
The slew rate should be above the following;
P wave Acute 0.6 to 1.7 v/s
Chronic 0.5 to 1.5 v/s
R wave Acute 0.8 to 2.0 v/s
Chronic 0.6 to 1.5 v/s
Slew rates below these values can lead to far field sensing or failure to sense
intrinsic activity. As the lead matures the slew rate will decrease by
approximately 40 % and therefore the intrinsic deflection may not be enough
to trigger the pacemaker once the lead enters the chronic phase.
The slew rate is measured in Volts/second (V/s).
D:PACING MANUAL.doc

INTRACARDIAC ECG
The intracardiac ECG recorded from the tip of the implanted electrode (known
as the ID – ‘intrinsic deflection’) can be used for the following:
(a) To check for capture
(b) To establish large amplitude of intrinsic waves (correlate to
measured P and R waves)
(c) To check current of injury
(d) To check for the presence or absence of retrograde P waves.
This can exclude the likely event of PMT in a DDD system
(e) The intrinsic deflection in the acute lead is usually
(i) bi-phasic (58 %)
(ii) monophasic positive (30 %)
(iii) monophasic negative (12 %)
ACUTE VENTRICULAR EGM
Current of injury is seen as
ST segment elevation. The
intrinsic deflection (large
rapid bi-phasic signal)
should coincide with the
surface QRS.
CHRONIC VENTRICULAR EGM
The Current of injury
should decrease leaving an
iso-electric ST segment in
the chronic lead.
The atrial EGM is quite similar to but smaller than the ventricular Electrogram.
Ideal ventricular electrode EGM measurements include:
(i) R wave of at least 4mv
(ii) Slew rate of at least 1.5mv/s
(iii) Current of injury of at least 2mv
D:PACING MANUAL.doc

FIXATION TESTS
Once the measurements are completed, it is advisable to check a stable lead
position. This is particularly important with passive fixation leads, although
displacement should not be ruled out with active fixation leads and therefore,
fixation tests should be performed with these leads also.
The output of the PSA is set to twice threshold or a 1volt minimum value.
Pacing with capture should be observed. The patient is asked to perform any
or all of the following:
(i) deep breathing
(ii) coughing
(iii) sniffing
X-Ray Screening is advised to observe for excessive lead movement and
pacing and capture observed throughout. If excessive movement or failure to
capture is seen, the lead should be repositioned.
DIAPHRAGMATIC TWITCHING
A final stimulation test should be performed to check that diaphragmatic
stimulation does not occur. This may be caused by inappropriate stimulation
of the phrenic nerve that innervates the diaphragm or direct stimulation
through a thin walled right ventricle or RV puncture.
A high output establishing pacing and capture should be performed.
Observation of the diaphragm with X-Ray screening and palpation of the
diaphragm area performed.
If twitching does occur then the electrode should be repositioned.
If the threshold is low, then reprogramming the pacemaker to a slightly lower
output may be considered and eradicate the twitching. However, reducing the
output is not an ideal solution initially as the stimulation threshold may rise
over the first twelve weeks, possibly leading to failure to capture.
LJB.MAI.001.02
D:PACING MANUAL.doc

PACING MODES
1ST
LETTER – CHAMBER PACED
2ND
LETTER – CHAMBER SENSED
3RD
LETTER – MODE OF ACTION
4TH
LETTER ( R ) – RATE MODULATION
5TH
LETTER – ANTITACHYCARDIA CAPABILITIES
(PACING, SHOCKING, DUAL)
D:PACING MANUAL.doc

AAI(R)
Chamber paced – atrium
Chamber sensed – atrium
Mode of action - inhibited
AAI
Indications
Sinus node dysfunction, with an intact AV node
AAI pacing gives a physiological response i.e. AV synchrony
Contra-indications
Presence of AV block
Presence of atrial tachyarrhythmias (AF/AFL)
AAIR
Indications
Are the same as for AAI but with the absence of chronotropic response
Contra-indications
Are the same as for AAI or patients who are unable to tolerate high rates
D:PACING MANUAL.doc

VVI(R)
Chamber paced – ventricle
Chamber sensed – ventricle
VVI
Indications
Sinus node dysfunction’s
AV block
Ideally VVI mode should be used for AV block with the presence of chronic
atrial tachyarrhythmias
Contra-indications
In the presence of pacemaker syndrome
VVIR
Indications
Are the same as for VVI but where there is an indication for rate response
Contra-indications
Are the same as for VVI or patients who are unable to tolerate high rates
DDD(R)
D:PACING MANUAL.doc

Chamber paced – Dual
atrium and ventricle
Chamber sensed – Dual
atrium and ventricle
Mode of action – Dual
Inhibited and Triggered
DDD
Indications
AV block in the presence of normal sinus node function
Contra-indications
Chronic / intermittent atrial tachyarrhythmias (see mode switch)
DDDR
Indications
AV block in the presence of sinus node dysfunction
Contra – indications
Are the same as for DDD or patients who are unable to tolerate high rates
D:PACING MANUAL.doc

SSIR
S – single
Either AAIR or VVIR
Chamber paced – atrium or ventricle
Chamber sensed – atrium or ventricle
Extra R – RATE RESPONSE
SENSORS
(1) activity
(2) minute volume
(3) QT interval measurements
(4) temperature
ACTIVITY is the most successful and therefore the most common.
There are two types of activity sensor
(1) piezo crystal
(2) accelerometer
D:PACING MANUAL.doc

Physiological response
AV synchrony
Chronotropic response
AAI pacing – AV synchrony is present
Chronotropic response is dependent upon the type of SA nodal
disease
AAIR pacing – AV synchrony is present
Chronotropic response is present
VVI pacing – No AV synchrony present
No chronotropic response present
VVIR pacing – No AV synchrony present
DDD pacing – AV synchrony is present
Chronotropic response is present, assuming normal SA nodal
function
DDDR pacing – AV synchrony is present
D:PACING MANUAL.doc

WHICH MODE FOR WHICH PATIENT
Consider
(1) ECG indications
(2) mobility
(3) age
ECG INDICATIONS
(1) Check for sinus node disease
(2) Check for AV nodal disease
MOBILITY
The more mobile a patient, the more physiological mode should be chosen.
AGE
Younger patients should be given a physiological mode
The choice of pacemaker should be dominated by the ECG indications and
always be discussed with the Physician prior to implantation.
Age and mobility should be considered but not have a strong influence over
the decision.
LJR..PM001.
D:PACING MANUAL.doc

TECHNICAL ASPECTS OF FOLLOW UP
When following up a patient with a pacemaker implanted there are
various technical aspects, which need to be observed.
1) battery assessment
2) electrode assessment
3) parameter settings
4) telemetry
5) Special Features
To perform all these tests the patient must be made comfortable and
an ECG monitored throughout. A three lead ECG is preferable with the ability
to perform full 12 lead ECG’s should be available. A pacing analyser must be
made available which has the facility to measure the pacing rate, pacing
interval and pulse duration of the pacing stimulus. Pacemaker programmers
suited to individual pacemaker models must be available. Resuscitation
equipment should be close by.
As well as the technical aspects of follow up, the medical aspects are also
important and need to be considered.
D:PACING MANUAL.doc

BATTERY ASSESSMENT
Once the pacemaker is implanted it must be checked regularly for battery
depletion.
(1) magnet measurements – each pacemaker has a fixed VOO rate, usually
higher than the programmed base rate, which occurs with application of a
magnet over the pacemaker site.
Magnet applied
If the patients intrinsic rhythm is faster than the magnetic rate then it may be
difficult to ensure capture, however the measurements of the pacemaker
stimulus can still be taken by the analyser to check for battery depletion.
D:PACING MANUAL.doc

The analyser measures the pacing rate (pulses per minute, ppm), pacing
interval (ms) and pulse duration of the pacing stimulus (ms). As the battery
depletes, the magnetic rate will gradually decreases until a certain rate is
reached. At this pacing rate the battery has reached the Recommended
Replacement Time (RRT) and further drop in magnet rate will give End Of Life
(EOL) indicators.
Each pacemaker type has different magnet rates at the Beginning Of Life
(BOL), RRT and EOL.
With some pacemakers, application of a magnet over the pacemaker will not
give a magnet response. This is due to in-built safety features, which can be
overridden with external programming. In this instance the magnet function
may have to be programmed ‘ON’ before any response to magnet is seen.
D:PACING MANUAL.doc

(2) Real-time telemetry (see later) - will also give readings of the battery
voltage, impedance and estimated longevity in most modern pacemakers.
As the battery depletes the voltage reduces and the impedance increases.
Most pacemaker battery voltages begin at 2.8v and will reach End of Life
at 2.4v.
D:PACING MANUAL.doc

ELECTRODE ASSESSMENT
(1) Stimulation threshold - is performed at each visit after implant. This is to
ensure electrode stability, to check for any acute rise in threshold due to the
scarring/oedematous process (during the first 6 weeks) and to further check
the lead integrity and function throughout the life of the pacing system.
Threshold is performed in the same way as at implant, reducing the output
voltage until loss of capture is seen. Some pacemakers only offer either
voltage or pulse-width thresholds as an automatic feature. If a more accurate
threshold is required a pulse duration threshold can also be measured at the
voltage threshold setting. This is called a strength duration threshold
measurement.
Some pacemaker types operate a vario threshold test, which usually has to
be programmed ‘ON’. With application of a magnet in this ‘vario’ mode the
vario threshold is performed at a higher rate than the programmed base rate.
With each stimulus the output is automatically decreased until after 16 pulses
D:PACING MANUAL.doc

the output has reached zero. Once loss of capture is seen, removal of the
magnet restores standard or programmed settings.
Most programmers offer an automatic threshold function, gradually reducing
the output until the test is terminated. The method of termination will vary
between programmers.
The results may be printed out and often a recommended output setting is
suggested.
Autocapture
Some pacemakers offer the option to perform an internal threshold looking for
ventricular depolarisation through the lead following an output at different
voltage settings. Reduction of the voltage setting is then automatically
adjusted in an ‘out of hospital’ setting.
D:PACING MANUAL.doc

(2) Electrode sensing function- should be established. A measurement of P or
R wave can assess satisfactory intrinsic activity, which can allow fine-tuning of
the sensitivity settings to be programmed. Some pacemakers allow an
automatic sensing threshold to be performed. The sensitivity is automatically
reduced and the test ended when failure to sense occurs.
(3) Lead Impedance – should always be checked. This may indicate fracture
(high
impedance) or insulation break (low impedance). Many models now offer a
continuous monitoring of lead impedance. Care should be taken to
incorporate slight changes from acute to chronic lead status.
D:PACING MANUAL.doc

PARAMETER REPROGRAMMING
(1) Output Voltage – Opinions vary as to when output reprogramming to a
lower value should take place. The oedematous reaction usually occurs within
the first six weeks after implant and therefore no further increase in threshold
should occur. Occasionally, late increases in threshold can occur although the
use of steroid-eluting electrodes has reduced the incidence of this. After the
1st
year of implant the lead should be stable and securely fixed to the
myocardial tissue. If the stimulation threshold has been low and stable for all
previous pacemaker checks then reprogramming the output to a lower value
can be done at this time.
Reprogramming the output to a lower level increases the longevity (life span)
of the pacemaker battery. It is usual to reprogram the output voltage to twice
the threshold voltage to retain a safety element in case a sudden increase in
stimulation threshold occurs.
Longevity
(yrs)
15
10
5
0
AT 4.0V
AT 2.0V
AT 7.0V
0.1 0.3 0.5 0.7 0.9 1.1 1.3 1.5
Pulse Width
It can be seen from the longevity table that a halving of output voltage
increases the longevity of battery by almost twice the number of years.
Changing the pulse width (duration) also has an effect although the battery life
saved is more significant with a decrease in output voltage than in pulse
duration.
If the stimulation threshold rises at any time then the output voltage setting will
need to be revised. Thought must be given as to the reason for the high
threshold with a view to further action being taken.
(2) Base Rate – reduction of base rate and hysteresis reprogramming can
routinely be programmed to facilitate intrinsic rhythm.
D:PACING MANUAL.doc

High base rates may need to be programmed, to suppress any arrhythmias in
those patients more at risk.
(3) AV Delay – can be lengthened to facilitate intrinsic AV conduction.
It can be shortened to enhance pre-exitation of ventricular depolarisation in
patients with Hypertrophic CardioMyopathy (HOCM).
(4) Activity Sensor – If the histograms and/or patient symptoms suggest that
the activity sensor in a rate responsive unit is ‘under active’ giving little or no
rate response (see below) then the activity threshold or rate response slope
can be reprogrammed.
If the histograms and/or patient symptoms suggest an ‘over-active’ sensor
(see below) then the activity threshold or rate response slope can be
reprogrammed.
Ventricular Rate
Histogram
D:PACING MANUAL.doc

(5) Sensitivity – If under or over sensing is seen at any time, the sensitivity of
the pacemaker must be reprogrammed to an optimal setting. Ideally the
sensitivity should be set to allow a 3 x safety margin for sensing intrinsic
activity.
(6) Polarity – If using Bipolar pacing leads, reprogramming the polarity either
to Bipolar sense and Unipolar pace can be considered. Whether the
preference is towards unipolar or bipolar pacing, the sensing function should
always be bipolar if possible. This will reduce inappropriate inhibition due to
extra-cardiac/corporeal interference.
(7) Maximum tracking/Maximum sensor (in rate responsive models) rate –
should be programmed appropriately for the age and activity level for each
individual patient.
(8) Mode switching in the DDD models – should be programmed ON.
Especially important for those patients with previous atrial arrhythmias.
D:PACING MANUAL.doc

TELEMETRY
(1) measured data - most pacemakers have telemetry functions either stored
or real-time, which allow detailed measurements of battery, lead status and/or
detailed histograms showing pacemaker activity, pacemaker sensor activity,
intrinsic cardiac activity, distribution of heart rates (paced and intrinsic), and
intrinsic P and R wave measurements.
Battery status:
Longevity (years and months)
Battery impedance (kΩ)
Battery voltage (volts,v)
These measurements allow close monitoring of battery levels, with the battery
voltage reducing and the battery impedance increasing over time.
Lead status:
Lead impedance (ohms,Ω)
Automatic threshold result
P/R wave measurements (millivolts, mv)
The lead impedance can be monitored regularly to check for lead fracture
(high impedance) or insulation break (low impedance).
D:PACING MANUAL.doc

(2) Histograms – Event, heart rate, frequency of mode switch and sensor
histograms all give useful and sometimes vital information that can aid
reprogramming and allow improved troubleshooting of pacemaker problems.
Event histogram
Shows amount of time or number of beats that have been sensed or paced by
the pacemaker.
D:PACING MANUAL.doc

Rate Histogram –
Shows the distribution of heart rates, either sensed or paced.
The heart rate histograms can indicate presence of high atrial or ventricular
rates.
D:PACING MANUAL.doc

Atrial Rate Histogram showing Atrial Arrhythmias
D:PACING MANUAL.doc

P/R wave amplitude histogram
Shows the distribution of measured intrinsic P or R waves.
D:PACING MANUAL.doc

The example below shows Normal P wave amplitude distribution.
The example below shows a variable P wave amplitude histogram, usually
seen in AF.
D:PACING MANUAL.doc

D:PACING MANUAL.doc

SPECIAL FEATURES
Many models now have special features incorporated. Mode switch has
become common place but other features are unique to individual models.
Rate drop response algorithms, atrial pacing therapies, high atrial and/or
ventricular rate counters and the storage of Intracardiac Electrograms (IEGM)
at the onset, during or at termination of these events is also available.
The stored IEGM’s which can establish the type of arrhythmia and
appropriateness of pacemaker modalities is crucial.
D:PACING MANUAL.doc

A special ‘Rate–drop therapy’ has been given and information regarding this
is shown in this histogram below.
D:PACING MANUAL.doc

MEDICAL ASPECTS
Once technical measurements have been taken, routine checks do not
usually need medical input, although it should be available if needed.
Special medical consideration should be given at the first pacemaker clinic
visit (between three and six weeks), although other medical problems at any
stage, should never be disregarded.
The 4 week check:
• establishes all technical aspects are satisfactory and medically a thorough
wound check is essential to check for infection at this time.
• re-enforcement of the positive aspects of pacing and the discussion of any
concerns may be included at this visit.
• investigation of symptoms, not established and/or solved at technical check.
Any cardiovascular disease present must always be considered in the re-
programming of the pacing system and any further treatments.
D:PACING MANUAL.doc

PROGRAMMABLE PARAMETERS
BASIC RATE
The basic rate is the lowest rate at which the pacemaker will output, and the
range varies between pacemakers.
When the pacemaker is programmed to a dual chamber mode, the highest
basic rate allowed is determined by the selected AV delay.
Often when the replacement time of the generator is reached, the base rate
interval will increase by a certain number of milliseconds (ms).
Clinical Advantages Of Reprogramming
1. Favour sinus rhythm
2. Improve cardiac output
3. Overdrive atrial and ventricular arrhythmias
4. Stand-by function
5. Diagnostic purposes
HYSTERESIS
The escape interval after a sensed intrinsic beat is greater than the escape
interval after a paced beat.
Clinical Advantage Of Reprogramming
To facilitate intrinsic rhythm, particularly useful if the intrinsic rate is similar to
the programmed base rate.
D:PACING MANUAL.doc

MAXIMUM TRACKING RATE (MTR)
Use of this parameter is limited to the DDD and DDDR pacing modes.
Regardless of the patient’s atrial rate, the ventricular pacing rate will never
exceed the programmed maximum tracking rate, if the pulse generator is
tracking the patient’s intrinsic atrial activity.
The pacing rate can exceed the programmed MTR during activity-responsive
pacing if the maximum sensor rate is programmed higher than the maximum
tracking rate (DDDR).
In the event that the patient develops an atrial rhythm faster than the selected
MTR, the pacemaker circuit may exhibit a Wenckebach effect – a progressive
lengthening of the P to V interval or even a 2:1 block.
When a P wave occurs within the atrial refractory period, the atrial event will
not be sensed, resulting in a dropped synchronous beat.
Therefore in the presence of atrial activity above the maximum tracking rate,
the P to V interval will progressively increase, eventually resulting in a
dropped ventricular beat – when the P wave falls within the refractory period,
similar to the physiological Wenckebach effect.
The maximum tracking rate is limited by the programmed AV interval as well
as the programmed atrial refractory period.
1. Allow high rates and maintain AV synchrony during vigorous exercise
2. Limit high rates due to tracking of atrial arrhythmias
D:PACING MANUAL.doc

PULSE AMPLITUDE AND DURATION
Pulse amplitude and duration are independently programmable and both have
an effect on energy of the pulse delivered.
The pulse amplitude mostly varies from 0v to 7.5 or 10v, the pulse duration
between 0ms and 1.0ms.
duration
amplitude
With new lead implants, outputs should be kept high to prevent loss of capture
due to early threshold rises.
Once the lead position has stabilised (usually one to three months) increases
in pulse generator longevity can be can be obtained by reducing the pulse
amplitude and duration.
Capture threshold therefore gives an indication as to the setting of these two
parameters.
1. Adjust output to suit individual capture thresholds, allowing a safety margin
2. Avoid muscle/nerve stimulation
3. Save energy and therefore extend longevity
amplitude
duration
D:PACING MANUAL.doc

REFRACTORY PERIOD
Immediately following a sensed or paced event, the pacemaker ceases to
respond to any signals occurring within the refractory period.
This prevents the pacemaker responding to a detected depolarisation signal
(terminal QRS) or repolarisation signals (T waves), which may result in timing
errors resulting in lower than programmed base rates.
The ventricular refractory period is always initiated by a sensed/paced
ventricular event.
The atrial refractory period is split into two segments.
1. The first segment starts with a sensed/paced atrial event and continues
until a sensed / paced ventricular event.
2. The second segment starts with a sensed / paced ventricular event and
continues for a programmed interval. This portion of atrial refractory period
is called the post ventricular atrial refractory period (PVARP).
Atrial refractory period ranges from approx. 200-500ms.
Ventricular from 200-500ms in non-tracking modes [DDI(R) and VVI(R)
modes] and is limited to 325ms in tracking modes [DDD(R) modes].
1. Prevent oversensing
2. Ensure arrhythmia sensing (AF/AFL) in mode switching devices
D:PACING MANUAL.doc

SENSITIVITY
If a cardiac signal of sufficient amplitude and frequency occurs during the
pacemakers ‘alert’ period, pacemaker output will be inhibited or triggered
according to the mode selected.
Sensing circuits are designed to specifically reject extraneous signals while
sensing P or R waves.
If intrinsic signals are low amplitude, the sensitivity should be reprogrammed
to a more sensitive level (lower value).
Conversely, if the pacemaker is responding to other extraneous signals,
reprogramming to a less sensitive setting may be employed (higher value).
A
B
C
D
A – NO SENSING
B – INTERMITTENT SENSING muscle
C – STABLE SENSING
D – SENSING OF MUSCLE NOISE cardiac
It is generally recommended that a sensing margin of 2-4 times the amplitude
of intrinsic cardiac signals be chosen, although in practice this is often difficult.
Atrial sensitivity usually varies between 0.5 and 5 mv.
Ventricular sensitivity between 1 and 10mv.
Adapt the sensitivity to the prevailing intrinsic cardiac signals.
D:PACING MANUAL.doc

AV DELAY
The AV delay defines the time interval between an atrial impulse and a
ventricular impulse.
The time interval between a sensed atrial and a paced ventricular event (PV
delay) should always be approx 25ms less than a paced atrial and paced
ventricular event (AV delay).
This difference between the PV and AV intervals is to compensate for the time
lag taken between the atrial impulse and atrial contraction.
This is to enable a consistent interval between atrial and ventricular
contraction, regardless of the mode of action (VAT or AV pacing).
PV delay
AV delay
The AV delay usually varies from 30ms to 300ms.
1. The PV delay should be 25ms less than the AV delay to maintain AV
synchronous contraction.
2. The AV/PV delay should be extended to facilitate intrinsic rhythm.
3. In HOCM patients the AV/PV delay should be shortened to maintain
ventricular pre- excitation due to ventricular pacing.
D:PACING MANUAL.doc

RATE RESPONSIVE AV DELAY
When RR AV delay is enabled, the PV interval during atrial tracking will
gradually shorten as the detected intrinsic atrial rate increases.
The time interval between a sensed atrial event and the ventricular impulse
(PV delay) will always be at least 25ms shorter than the programmed AV
delay, even when RR AV delay is disabled.
When RR AV delay is enabled, the PV interval will shorten further as the
sensed atrial rate increases.
If the device is programmed to DDDR with the RR AV delay enabled, the AV
delay will shorten as the pacing rate increases in response to patient activity.
This feature is intended to optimise cardiac output by mimicking the
decreasing PR interval which occurs in the normal heart as the atrial rate
increases.
D:PACING MANUAL.doc

BLANKING PERIOD
The “blanking period” is a short interval after each pulse output where the
pacemakers sensing circuits are completely blind, and NO sensing occurs.
Ventricular Blanking
A blanking period will momentarily occur in the ventricular sensing circuit,
coincident with any atrial output.
This feature is employed to prevent detection of an atrial output by the
ventricular sensing circuit which would result in ventricular output inhibition
and a reset of pulse generator timing.
This is known as “CROSSTALK”.
The range will usually vary between 13 and 50ms.
Atrial Blanking
A blanking period will momentarily occur in the atrial sensing circuit,
coincident with any ventricular output.
This feature is employed to prevent detection of a ventricular output by the
atrial sensing circuit which would result in attempts at inappropriate tracking
and would cause havoc in a mode switching device.
The range will usually vary between 50 and 150ms.
A short atrial blanking is useful to assist in the detection of atrial arrhythmias
in mode switching devices.
D:PACING MANUAL.doc

PMT OPTIONS
The PMT (Pacemaker Mediated Tachycardia) options are designed to
terminate PMTs if and when they occur in the DDD mode.
If consistent tracking at the maximum tracking rate occurs for a select number
of cycles, an attempt is made to break the PMT cycle by purposefully failing to
track a sensed retrograde P wave.
The detection criteria will vary between manufacturers and with recent
technology even consistent “VA” measurements can now be made to confirm
the presence of a PMT.
This option is not always programmable and this feature is often an integral
part of some pacemaker models.
D:PACING MANUAL.doc

POLARITY
Pulse polarity and sensing polarity is often independently programmable for
both atrial and ventricular chambers.
PULSE POLARITY CONFIGURATION
If unipolar configuration is selected, the distal tip electrode of the lead will
serve as the pacing cathode (-) with the uncoated portion of the pacemaker’s
titanium case serving as the anode (+).
If a bipolar configuration is selected, the distal electrode will continue to serve
as the pacing cathode (-) with the lead’s proximal ring electrode serving as the
pacing anode (+).
During bipolar pacing the generator’s titanium case is electrically isolated from
the pacing circuit.
1. Advantage of bipolar pacing is to eliminate the potential of pocket
stimulation.
2. The advantage of unipolar pacing is to produce a large stimulation artefact
which can be easily visualised on the surface ECG, promoting easy
interpretation.
SENSING POLARITY CONFIGURATION
If unipolar sensing is selected, the voltage difference between the pacing
lead’s distal electrode and the exposed area of the generator’s titanium case
will be sensed.
If bipolar is selected, the pacemaker will sense in a bipolar manner between
the lead’s distal and proximal electrodes.
Bipolar sensing reduces susceptibility to detection of myopotentials and
external electromagnetic interference.
D:PACING MANUAL.doc

SENSOR
Most sensor-driven generators incorporate an activity piesoelectric sensor
bonded to the inside of the generator case.
The sensor generates a signal in response to vibrations which result from
ambulation or repetitive upper body movements.
When the sensor is programmed “ON”, the sensor signal is processed to
allow an increase in pacing rate in response to activity.
MAXIMUM SENSOR RATE
The maximum rate allowed by the generator in response to activity.
The maximum sensor rate chosen is usually similar to the maximum tracking
rate.
Sensor rates higher than maximum tracking rates may be chosen in the
presence of paroxysmal atrial arrhythmias.
SLOPE
The programmed slope value determines the increase in pacing rate which
occurs at various levels of activity.
In general a low slope, low sensor level corresponds to a low level of patient
activity whereas a maximum slope, high sensor level corresponds to a high
level of patient activity.
Higher slopes will result in a greater increase in pacing rate than a low slope
for any level of activity.
D:PACING MANUAL.doc

THRESHOLD
The activity threshold is the minimum level the sensor signal has to reach
before allowing a pacing rate increase in response to activity.
At low activity threshold settings a pacing rate increase can be observed in
response to minimum activity.
At high activity threshold settings a much higher level of activity is required to
cause any pacing rate increase.
REACTION TIME (ACCELERATION TIME)
The value selected for the reaction time determines the minimum time allowed
for the sensor-driven rate to increase from base to maximum.
The programmed reaction time only applies to increases in sensor-driven
rates, not during atrial tracking.
A short reaction time will allow the pacing rate to increase rapidly in response
to patient activity.
A long reaction time will force a slow increase in pacing rate.
The range will usually vary between 0.5 to 2.5 minutes, although some
models have pre-determined times giving a range from very low to very high.
RECOVERY TIME (DECELERATION TIME)
The value selected for recovery time determines the minimum time required
for a decrease in pacing rate from the maximum sensor-driven rate to the
base rate.
This feature is intended to prevent an abrupt decrease in pacing rate
concurrent with the conclusion of patient activity.
A long recovery time will result in a slow decrease in pacing rate when the
patients activity level decreases.
A short recovery time will allow the pacing rate to decrease more rapidly.
The range will usually vary between 2.5-5 minutes.
D:PACING MANUAL.doc

MODE SWITCH
Modern technological advances allow this feature as routine on most
commercially available DDD pacemakers.
In the presence of an atrial arrhythmia, the generator switches from a tracking
mode (DDD) to a non-tracking mode (DDI).
To prevent the rate suddenly dropping from a tracking mode (VAT pacing) to
base rate, it is recommended that sensor-driven modes are present during the
time of mode switch.
In this way the mode will switch from a tracking mode (DDD) to a sensor-
driven non-tracking mode (DDIR).
Detection criteria of atrial arrhythmias will vary between manufacturers.
Reprogramming of some basic parameters will often assist in the true sensing
and therefore the true detection of atrial arrhythmias as soon as possible.
1. Atrial sensing to bipolar
2. Shorten atrial blanking
3. Increase atrial sensitivity (lower value)
LJR..PP001.00
D:PACING MANUAL.doc

COMPLICATIONS OF FOLLOW UP
FAILURE TO CAPTURE
Failure to capture occurs when more energy is required to stimulate the heart.
VVI
LOC (V)
AAI
LOC (A)
DDD
LOC (V)
DDD
LOC (A)
D:PACING MANUAL.doc

UNDERSENSING – FAILURE TO SENSE
VVI
Failure to
Sense (V)
AAI
Failure to
Sense (A)
Failure to sense occurs when the pacemaker fails to see intracardiac signals
that are the result of an intrinsic beat.
In this case the sensitivity of the pacemaker is inadequate, this is called
UNDERSENSING.
D:PACING MANUAL.doc

OVERSENSING
(A) FAR FIELD SENSING
Inappropriate inhibition due to inappropriate sensing of a cardiac source.
The pacemaker is OVERSENSING.
P waves - sensed by a ventricular system (VVI)
QRS waves – sensed by an atrial system (AAI)
T waves – usually in ventricular systems.
(B) EMG (electromyographic) INHIBITION (oversensing)
Inappropriate inhibition due to the pacemaker sensing myopotentials from
skeletal muscle. (Usually pectoral muscle stimulation).
Seen in unipolar systems.
Muscle Tremor
D:PACING MANUAL.doc

(C) CROSS TALK (oversensing)
Inappropriate inhibition due to one electrode sensing the output from the other
electrode. Occurs in DDD mode only.
(D) EXTRA-CORPOREAL SOURCE (oversensing)
Electromagnetic
Electrical
D:PACING MANUAL.doc

EXTRA-CARDIAC STIMULATION
(A) SKELETAL MUSCLE STIMULATION
Pectoral muscle/rectus sheath muscle stimulation
Skeletal muscle stimulation occurs with current from the pacing system
directly stimulating nearby tissue.
The indifferent plate of the pulse generator (in a unipolar system) must be
positioned away from muscle tissue.
A break in lead insulation close to the generator site may allow current
leakage to directly stimulate nearby muscle.
Incomplete lead connection with pacemaker.
(B) DIAPHRAGMATIC STIMULATION
Direct – Ventricular lead apical position may directly stimulate the diaphragm.
This may occur with thin walled ventricles or myocardial tissue perforation.
Indirect – Atrial appendage lead position may indirectly stimulate the
diaphragm via stimulation of the phrenic nerve.
D:PACING MANUAL.doc

PACEMAKER MEDIATED TACHYCARDIA
A tachycardia due to the tracking of retrograde P waves in the DDD mode,
usually initiated by atrial or ventricular ectopics.
Many pacemakers have PMT protection algorithms that extend the atrial
refractory period if maximum tracking occurs for an extended period of time.
This will encourage the retrograde P wave to fall within the refractory period
and failure to track this P wave will break tachycardia.
Permanent programming of the atrial refractory period may be needed and to
allow high maximum tracking rates to be programmed, the AV delay may
need to be shortened.
PACEMAKER SYNDROME
Some patient’s experience dizziness or lethargy after implantation of a VVI
pacing system.
The loss of AV synchrony may lead to a reduced cardiac output.
Retrograde conduction of a P wave can cause contraction of the atria against
a closed AV valve.
VVI pacing alone with a normal sinus P wave or normally conducting atria can
cause a reduced cardiac output leading to the symptoms above.
WOUND INFECTION
If the pacemaker site becomes infected early Antibiotic treatment is
necessary.
Failure to treat infection may lead to the removal of pacemaker and leads.
This is an attempt to prevent the spread of infection to the myocardium and so
prevent Endo/Myocarditis.
D:PACING MANUAL.doc

EROSION
Erosion is most likely to occur with an infection, however erosion of the pulse
generator can be an isolated occurrence.
Re-siting the generator deeper and more medially can solve the problem.
It is important to exclude the presence of low-grade infection.
PACEMAKER TWIDDLERS SYNDROME
Constant handling of the pacemaker can lead to fracture, displacement and
even knotting of the lead.
Movement of the pacemaker can also cause erosion of the generator.
PACEMAKER ALLERGY
Pacemaker allergy is thought to be very rare and the symptoms can include
erosion and/or painful pacemaker site.
It is important to exclude a low-grade infection.
FAILURE TO HEAL
This is usually due to infection.
LJR.CFU.001.01
D:PACING MANUAL.doc

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