What are they?
• ICD (or Implantable Cardioverter Defibrillator):
– a small battery powered device implanted into a patient
– detects an arrhythmia it delivers a shock to “restart” the heart, and
restore a sinus rhythm.
– A small battery powered device, implanted into a patient
– Paces the heart when normal rhythm is slow, when there is a heart
block not allowing the ventricles to contract when the SA node fires,
or any arrhythmia causing a slow rate.
INDICATIONS• Sinoatrial (SA) node—sick sinus syndrome,
• bradycardia, hypersensitive carotid sinus
syndrome, or vasovagal syncope
• Atrioventricular (AV) node—second-degree
block or third-degree AV block
• Trifascicular block or bifascicular block.
• Right bundle branch block (RBBB) and left
anterior or posterior hemiblock.
• congenital long Q-T syndrome .
• Cardiomyopathy—patients with medically
refractory hypertrophic obstructive
• decompensated heart failure in patients with
dilated cardiomyopathy despite optimal
• Alternating left bundle branch block (LBBB)
Three-letter and five-letter identification codes
y & rate
R = Rate
• In the 1970s, the Intersociety Commission for Heart
Disease Resources (ICHD) suggested a classification code,
which is now widely accepted.
• The original nomenclature involved a three-letter
identi fication code, as shown in the first three columns
• In 1980, this code was extended to five letters; the last
two letters can be deleted when not applicable.
• In 1987, the NASPE (now known as the Heart Rhythm
Society) and BPEG adopted a new five-letter code to
describe the operation of implantable pacemakers.
What are the modes of pacing?
• Asynchronous pacing.
• Single-chamber demand pacing.
• Dual-chamber atrioventricular (AV) sequential
• Asynchronous or fixed-rate (e.g., AOO, VOO,
DOO) modes pace at a preset rate independent
of the inherent heart rate. They can be atrial,
ventricular, or dual chamber.
• Complications- Competition and ventricular
• VF occurs when the pacing spike is delivered
during ventricular repolarization, very rare.
SINGLE CHAMBER DEMAND PACING
• Single-chamber demand pacing (e.g., AAI, VVI) paces at
a preset rate only when the spontaneous heart rate
drops below the preset rate.
• The ventricular-inhibited pacer is the most popular
type and is suppressed by normal electrical activity of
the QRS complex.
• For example, if patient's device is programmed to VVI
70/min, the device would pace in the ventricle only
when the native ventricular rate fall below 70/min.
• Once the native ventricular rate resumed above 70
/min, the device would sense this activity and inhibit
• Single-chamber demand pacing in the atrium functions
in a similar way but is rarely used alone in the United
DUAL CHAMBER AV-SEQUENTAIL PACING
• It requires two pacemaker leads, one in the right atrium and one in the
• The atrium is stimulated to contract first then after an adjustable PR
interval the ventricle is stimulated to contract.
if device is programmed to DDD 70/min with a PR interval (AKA: AV delay)
of 200 ms,
1st the atrium is paced if the intrinsic heart rate falls below 70/min.
the device will wait for 200 ms to sense intrinsic ventricular activity.
If it does not see intrinsic activity within 200 ms, it will then pace in the
ventricle as well.
DDD pacemakers can also pace in the ventricle in response to intrinsic
• Ex- if the intrinsic atrial rate is 80/min
the device would inhibit pacing in the atrium because the
base rate is set to 70/min
As the device is capable of sensing and pacing in both
wait 200 ms from the time of the intrinsic atrial activity
and watch for intrinsic ventricular activity
If there is no intrinsic ventricular activity occurring within
200 ms from the intrinsic atrial activity,
pace in the ventricle.
What are the parts of a pacemaker?
A Pacemaker System consists of a Pulse Generator plus
• Pulse generator- power source or battery
• Cathode (negative electrode)
• Anode (positive electrode)
• Body tissue
• Contains a battery that provides the energy
for sending electrical impulses to the heart
• Houses the circuitry that controls pacemaker
• Casing (can)
• Connector (header)
– Leads plug into ports
– Diodes, resistors, oscillator, microchips
– The largest single component inside the pulse
– Lithium iodide
• Deliver electrical impulses from the pulse
generator to the heart
• Sense cardiac depolarisation
• Position within the heart
– Endocardial or transvenous leads
– Epicardial leads
• Fixation mechanism
– J-shaped used in the atrium
• Passive fixation
– The tines become
lodged in the
• Active Fixation
– The helix (or screw) extends into the endocardial
• Epicardial are Leads applied directly to the
• Cathode:-An electrode that is in contact with the
• Negatively charged
• Anode:-receives the electrical impulse after
depolarization of cardiac tissue
• Positively charged when electrical current is
• Flows through the tip
• Stimulates the heart
• Returns through body fluid
and tissue to the PG (anode)
• Patient serves as the
interference occurs more
often in unipolar leads
Contains a lead with 2 electrodes in the heart
• Flows through the tip electrode
located at the end of the lead wire.
• Stimulates the heart.
• Returns to the ring electrode above
the lead tip.
• Provides a built-in ground lead.
• Circuit is completed within the heart
• Provides more contact with the
endocardium; needs lower current
• Less chance for cautery interference
Rate response pacing
• Various activity-detecting systems have been
developed in years past to create a reliable rateresponsive pacemaker.
• muscle movement, respiratory rate, minute ventilation,
central venous temperature, QT interval, myocardial
contractility ,oxygen saturation and pH in mixed venous
blood, and ventricular depolarization gradient.
• Ex. patients who are subjected to mechanical
hyperventilation (e.g., neurosurgery) can experience an
increase in the rate of pacing.
• As a result, most device manufacturers recommend
disabling the rate-responsive features before surgery.
• If reprogramming the device is not readily available, a
magnet may be placed over the pacemaker site to
temporarily convert it to asynchronous pacing.
How to detect of type of pacing.
• In atrial pacing, an electrical spike appears before
the P wave and the QRS complex is usually
• In ventricular pacing, the electrical spike is
followed immediately by a widened QRS complex.
• In AV sequential pacing, there are two spikes,
one before the P wave and another preceding the
• The maximum pulse amplitude- 7.5 volts (V).
• The maximum pulse width -1.5 msec
• Fluctuations in the pacing threshold in the first few
weeks after a pacing lead has been implanted.
• There is a sharp rise in the pacing threshold - the first
2 weeks because of tissue reaction around the tip of
the electrode despite the presence of steroid
embedded at the tip.
• Then it falls to two to three times after the scar
formation. So the pacing output be at least two times
the threshold value or three times the pulse width of
the threshold value.
• The most modern day PPM have preset sensitivity
settings approximately 2.0 to 3.0 mV.
• Impedance between 250 and 1,300 ohms.
biventricular permanent pacemaker (PPM) or cardiac
resynchronization therapy (CRT) device
• These devices are capable of pacing both the left
ventricular septum (through a pacemakerlead in
the right ventricle) and the left ventricular lateral
free wall simultaneously (through a pacemaker
lead in the coronary sinus), therefore allowing for
activation of the entire left ventricle at the same
• INDICATIONS• severe cardiomyopathy (EF< = 35%),
• LBBB with New York Heart Association (NYHA)
class III or class IV symptoms despite optimal
LIFE SPAN OF PPM AND ICD
• 5 to 10 years - dual-chamber pacing
• 7 to 12 years -single-chamber pacing.
• The silver-vanadium oxide batteries used in
ICDs typically last for 5 to 8 years
What is an ICD?
• An ICD system consists of a pulse generator and leads for
tachyarrhythmia detection and therapy.
• ICDs provide• antitachycardia and antibradycardia pacing;
• synchronized (cardioversion) or nonsynchronized
• the pulse generator is a self-powered computer within
sealed titanium casing (can).
• One or two (in series) 3.2 V lithium–silver vanadium oxide
batteries with high power density are used to power the
pulse generator, ci rcuitry, and aluminum electrolytic
• defibrillatory shocks of 850 V -modern day devices.
• Modern ICDs use transvenous lead systems for
sensing, pacing, and shocks. Epicardial leads
are still used in infants and small children.
• Current ICDs have many programmable
features, but essentially they measure each
cardiac R-R interval and categorize the rate as
normal, too fast (short R-R interval) or too
How does it work?
• The internal computer decide between
antitachycardia pacing and shock.
• If shock is chosen, an internal capacitor is
charged which takes 5 to 13 seconds.
• It reconfirms ventricular tachycardia (VT) or
ventricular fibrillation (VF) after charging to
prevent inappropriate shock therapy.
• Typically, ICDs deliver no more than six shocks per
• Once a shock is delivered, the ICD will redetect to
determine whether or not the shock successfully
terminated the arrhythmia.
• A tachycardia episode is considered terminated
when sinus rhythm has been restored.
INDICATIONS OF ICD
• Cardiac arrest resulting from VT/VF
• Spontaneous sustained VT with structural heart disease
• Syncope of undetermined origin.
• Ischemic cardiomyopathy (EF ≤30%) without a recent myocardial
infarction (within the last 4 weeks) or revascularization in the past 3
• Ischemic or nonischemic dilated cardiomyopathy (EF ≤35%) with
New York Heart Association (NYHA) class II or III heart failure
symptoms stable for the past 9 months.
• Brugada syndrome—right bundle branch block (RBBB) and ST
segment elevation leads V1 to V3
• Arrhythmogenic right ventricular dysplasia
• Long and short Q-T syndrome
• Hypertrophic obstructive cardiomyopathy
PRE-OP EVALUATION OF A PT WITH
• Routine systemic workup, paying particular
attention to cardiovascular disorders.
• Special attention should be paid to the history
• Symptoms, and signs of myocardial infarction
(MI), congestive heart failure, and arrhythmia.
• Serum electrolytes, especially potassium level,
must be in the normal range.
Patient with a
cardiac rhythm management device (CRMD)
• Establish whether a patient has a CRMD
• Define the type of CRMD
• Determine dependency on pacing function of
• Determine CRMD function.
• To Determine a patient has a CRMD(a) patient interview, medical records review, review of
available chest x-ray films ,electrocardiogram, or any
available monitor or rhythm strip information
(b) Physical examination (checking for scars, palpating for
• To Define the type of device
(a) obtaining the manufacturer's identification card from
the patient or other source,
(b) chest x-ray studies if no other data are available, or
(c)referring to supplemental resources e.g.,
manufacturers' databases, pacemaker clinic records,
consultation with a cardiologist.
(a) battery life
(b) programmed pacing mode such as VVIR, DDDR,
(d) intrinsic rhythm,
(e) magnet rate and rhythm
(f) prior recorded arrhythmic events
(g) pacemaker lead parameters (including pacing
threshold, ability to sense intrinsic activity, and
Evaluate if the pacemaker or ICD is
• Slowing the intrinsic heart rate to a rate below that of the
pacemaker by carotid massage or a Valsalva maneuver.
• Carotid massage to slow the heart rate should be used
cautiously because it could result in an arteriosclerotic
plaque embolizing to the cerebral circulation.
• If the rate does not slow down enough for the pacemaker
to take over the ventricle, device can be tested by placing a
magnet over it to convert it to a fixed-rate pacing mode.
• The rate at which the pacemaker will pace in the presence
of a magnet varies among device manufacturers and is
dependent on the battery life.
• Determining whether electromagnetic interference (EMI) is likely
to occur during the planned procedure;
• Determining whether reprogramming the cardiac rhythm
management device (CRMD) pacemaking function to an
asynchronous pacing mode or disabling any special algorithms is
• Suspending antitachyarrhythmia functions if present;
• Advising the surgeon performing the procedure to consider use of a
bipolar electrocautery system or ultrasonic (harmonic) scalpel to
minimize potential adverse effects of EMI on the pulse generator or
• Assuring the availability of temporary pacing and defibrillation
• Evaluating the possible effects of anesthetic techniques on CRMD
function and patient-CRMD interactions.
• reprogramming the device to asynchronous pacing mode before
surgery as electrocautery during surgery may inhibit pacing function
• continuous electrocardiogram (ECG)
• continuous peripheral pulse monitorings1. palpation of the pulse,
2. auscultation of heart sounds,
3. pulse plethysmography or oximetry,
4. a tracing of arterial wave form,
5. or ultrasound peripheral pulse monitoring.
• Arterial line and central venous pressure or pulmonary
artery pressure monitoring may be used only if the
patient has poor ventricular function.
• The “artifact filter” on the ECG monitor should be
disabled in order to detect the pacing spikes.
• The ECG monitor should be set in diagnostic mode
instead of monitoring mode.
• A complete array of drugs and equipment
must be immediately available for
• The minimal requirements include,
electrocardiograph (ECG) monitor,
• a transcutaneous external pacing and
• DC defibrillator, and the usual drugs for
• The electrodes should be placed as far (more
than 6 in. or 15 cm) from a cardiac rhythm
management device (CRMD) as possible.
• The electrodes are positioned perpendicular
to the CRMD system.
• There are three recommended electrode
The right arm (RA) electrode
placed under the left scapula
and the left leg (LL) electrode at
apex of the heart
• Apex-anterior placement. The RA electrode placed under the
right clavicle and the LL electrode at the apex of the heart
• Apex-posterior placement. The RA electrode placed over the
right scapula and the LL electrode at the apex of the heart
A: Apex—anterior placement with both
pads placed anteriorly. B and C: Apex—
posterior placement are shown with the
the left prepectoral region (B) and the right
pectoral region (C).
• During electrocautery, the electrocardiogram is
frequently useless because of interference.
• The best monitor available to determine if inhibition is
taking place is a hand on the pulse.
• The precordial or esophageal stethoscope, pulse
oximeter, or blood pressure is also acceptable.
• The responses of pacemakers to electrocautery or
other electromagnetic interference
• Inhibition of pacing
• Asynchronous pacing
• Reset to Backup mode
• Myocardial burns, rare
• Ventricular fibrillation (VF),
• precautions should be taken to minimize the effects of
• Place the cautery grounding plate as close to the operative
site and as far from the cardiac rhythm management device
• For some cases, the grounding plate might need to be
placed contralateral to the CRMD generator.
• Cautery should not be used within 15 cm of the
• Limit cautery use to 1-second bursts every 10 seconds to
prevent repetitive asystolic periods.
• If the pacemaker is inhibited by the cautery, place a highpowered magnet over pacemaker to convert it to fixed-rate
• Using bipolar electrocautery forceps or ultrasonic
(harmonic) scalpel reduces electromagnetic interference.
• ESWL-ESWL is no longer contraindicated for patients with
The only exception to this general statement is the abdominally
placed pacemaker generators. Because these generators are in the
blast path of the shock wave, such patients should not be treated
However, most transvenous pacemaker generators are placed in a
pectoral location that is at a safe distance from the blast path.
• Consider preoperative disabling of atrial pacing if the lithotripsy
system triggers on the R wave.
• Although most pacemakers are not affected by ESWL, sometimes it
may cause pacemaker malfunctions• Pacing irregularity
• Oversensing of asynchronous shocks
• Damage to rate-sensing piezoelectric crystal
• Intermittent inhibition of ventricular output in dual-chamber
• There may be a rate increase in a rate-response
(adaptive) pacemaker after ESWL shocks.
Therefore,special precautions should be taken
• an alternative means of pacing, suchas transcutaneous
pacing, should also be available in case the pacemaker
becomes permanently damaged.
• Low-energy shock waves (< 16 kV) should be used
initiall y; then the energy level is gradually increased
while pacemaker function is monitored carefully.
• It is best to disable tachycardia detection of an ICD
during ESWL and to thoroughly test the ICD following
• ECT appears safe for patients with pacemakers
because little current flows within the heart due
to the high impedance of body tissues.
• However, the seizure and succinylcholine
fasciculations may generate sufficient
myopotentials for pacemaker inhibition (unipolar
devices) or ventricular tracking (adaptiverate
• So it is advisable to program the pacemaker to
(asynchronous) mode for pacemaker-dependent
• An external pacemaker should also be available.
• ICDs-tachycardia detection is disabled before ECT
and reprogrammed to its original programmed
• MRI is generally contraindicated in patients with a CRMD.
• If MRI must be performed, consultation with the ordering
physician, the patient's cardiologist, the diagnostic radiologist and
the CRMD manufacturer.
• MRI can cause rapid pacing, inhibition, resetting of DDD
pacemakers, and transient reed switch malfunction with
• Serious malfunction with no output or rapid pacing may occur
because pulsed energy from MRI can enter the lead by capacitive
coupling and cause rapid ventricular pacing
• When an MRI is considered absolutely essential, it is reasonable to
program the pacemaker to its lowest voltage and pulse width or to
OOO mode, provided the patient has an adequate underlying
• The pulse waveform should be closely monitored in pacemakerdependent patients and an external pacemaker and defibrillator
should be available.
• Device function must be checked after MRI.
• Cardiac rate and rhythm should be
continuously monitored throughout the
• Backup pacing capability and cardioversiondefibrillation equipment should be
immediately available at all times
Pacer fails to detect an intrinsic rhythm
Patient may feel “extra beats”
If an unneeded pacer spike falls in the latter
portion of T wave, dangerous
tachyarrhythmias or V fib may occur (R on T)
TX: Increase sensitivity of pacer.
Pacemaker doesn’t sense patient’s own
beat and fires
Pacer interprets noncardiac electrical signals as
originating in the heart
• Detects extraneous signals such as those
produced by electrical equipment or the activity
of skeletal muscles (tensing, flexing of chest
• Inhibits itself from pacing
• On ECG: pauses longer than the normal pacing
interval are present
• Often, electrical artifact is seen
• Deprived of pacing, the patient suffers CO,
• Most often due to sensitivity being
programmed too high
TX: Reduce sensitivity
Pacemaker senses heart beat even though it
isn’t beating. Note the long pauses.
Pacer’s electrical stimulus (pacing) fails to
depolarize (capture) the heart
• There is no “failure to pace”
• Pacing is simply unsuccessful at stimulating a
• ECG shows pacer spikes but no cardiac
TX: threshold/output strength or duration