Basic Pacing Concepts
Part I
Objectives
Identify the components of pacing systems and their
respective functions
Define basic electrical terminology
Describe the relationship of amplitude and pulse width
defined in the strength duration curve
Explain the importance of sensing
Discuss sources of electromagnetic interference (EMI) and
patient/clinician guidelines related to these sources
Understand the need for and types of sensors used in rate
responsive pacing
Pacing Systems
The Heart Has an Intrinsic Pacemaker
The heart generates electrical impulses that
travel along a specialized conduction pathway
This conduction process makes it possible for
the heart to pump blood efficiently
During Conduction, an Impulse Begins in the
Sinoatrial (SA) Node and Causes the Atria to Contract
Atria
Sinoatrial (SA) Node
Ventricles
Atrioventricular (AV) Node
Then, the Impulse Moves to the Atrioventricular (AV) Node and Down
the Bundle Branches, Which Causes the Ventricles to Contract
Atria
SA node
Ventricles
AV node
Bundle branches
Diseased Heart Tissue May:
Prevent impulse
generation in the SA
node
SA node
Inhibit impulse
conduction
AV node
Implantable Pacemaker Systems
Contain the Following Components:
Lead wire(s)
Implantable pulse
generator (IPG)
Pacemaker Components Combine with
Body Tissue to Form a Complete Circuit
Pulse generator: power
source or battery
Lead
Leads or wires
Cathode (negative
electrode)
Anode (positive
electrode)
Body tissue
IPG
Anode
Cathode
The Pulse Generator:
Contains a battery
that provides the
energy for sending
electrical impulses to
the heart
Houses the circuitry
that controls
pacemaker
operations
Circuitry
Battery
Leads Are Insulated Wires That:
Deliver electrical
impulses from the
pulse generator to
the heart
Sense cardiac
depolarization
Lead
Types of Leads
Endocardial or transvenous leads
Myocardial/Epicardial leads
Transvenous Leads Have Different
“Fixation” Mechanisms
Passive fixation
– The tines become
lodged in the
trabeculae
(fibrous meshwork)
of the heart
Transvenous Leads
Active Fixation
– The helix (or screw)
extends into the
endocardial tissue
– Allows for lead
positioning
anywhere in the
heart’s chamber
Myocardial and Epicardial Leads
Leads applied directly to
the heart
– Fixation mechanisms
include:
Epicardial stab-in
Myocardial screw-in
Suture-on
Cathode
An electrode that is
in contact with the
heart tissue
Negatively charged
when electrical
current is flowing
Cathode
Anode
An electrode that
receives the electrical
impulse after
depolarization of
cardiac tissue
Positively charged
when electrical
current is flowing
Anode
Conduction Pathways
Body tissues and
fluids are part of the
conduction pathway
between the anode
and cathode
Anode
Tissue
Cathode
During Pacing, the Impulse:
Begins in the pulse
generator
Flows through the lead
and the cathode (–)
Stimulates the heart
Returns to the anode (+)
Impulse onset
*
A Unipolar Pacing System Contains a Lead with Only One
Electrode Within the Heart; In This System, the Impulse:
Flows through the tip
electrode (cathode)
Stimulates the heart
Returns through
body fluid and tissue
to the IPG (anode)
+
Anode
Cathode
A Bipolar Pacing System Contains a Lead with Two
Electrodes Within the Heart. In This System, the Impulse:
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
Anode
Cathode
Unipolar and Bipolar Leads
Unipolar leads
Unipolar leads may
have a smaller
diameter lead body
than bipolar leads
Unipolar leads
usually exhibit larger
pacing artifacts on
the surface ECG
Bipolar leads
Bipolar leads are less
susceptible to
oversensing
noncardiac signals
(myopotentials and
EMI)
Coaxial Lead
Design
Lead Insulation May Be Silicone
or Polyurethane
Advantages of Silicone-Insulated Leads
Inert
Biocompatible
Biostable
Repairable with medical adhesive
Historically very reliable
Advantages of
Polyurethane-Insulated Leads
Biocompatible
High tear strength
Low friction coefficient
Smaller lead diameter
A Brief History of Pacemakers
Single-Chamber and Dual-Chamber
Pacing Systems
Single-Chamber System
The pacing lead is
implanted in the
atrium or ventricle,
depending on the
chamber to be paced
and sensed
Paced Rhythm Recognition
AAI / 60
Paced Rhythm Recognition
VVI / 60
Advantages and Disadvantages of
Single-Chamber Pacing Systems
Advantages
Disadvantages
Implantation of a
single lead
Single ventricular lead
does not provide AV
synchrony
Single atrial lead does
not provide ventricular
backup if A-to-V
conduction is lost
Dual-Chamber Systems Have Two Leads:
One lead implanted
in the atrium
One lead implanted
in the ventricle
Paced Rhythm Recognition
DDD / 60 / 120
Paced Rhythm Recognition
DDD / 60 / 120
Paced Rhythm Recognition
DDD / 60 / 120
Paced Rhythm Recognition
DDD / 60 / 120
Most Pacemakers Perform Four Functions:
Stimulate cardiac depolarization
Sense intrinsic cardiac function
Respond to increased metabolic demand by
providing rate responsive pacing
Provide diagnostic information stored by the
pacemaker
General Medtronic Pacemaker Disclaimer
INDICATIONS
Medtronic pacemakers are indicated for rate adaptive pacing in patients who may benefit from increased pacing rates concurrent with increases in activity (Thera, Thera-i,
Prodigy, Preva and Medtronic.Kappa 700 Series) or increases in activity and/or minute ventilation (Medtronic.Kappa 400 Series).
Medtronic pacemakers are also indicated for dual chamber and atrial tracking modes in patients who may benefit from maintenance of AV synchrony. Dual chamber modes
are specifically indicated for treatment of conduction disorders that require restoration of both rate and AV synchrony, which include various degrees of AV block to maintain
the atrial contribution to cardiac output and VVI intolerance (e.g., pacemaker syndrome) in the presence of persistent sinus rhythm.
9790 Programmer
The Medtronic 9790 Programmers are portable, microprocessor based instruments used to program Medtronic implantable devices.
9462
The Model 9462 Remote Assistant™ is intended for use in combination with a Medtronic implantable pacemaker with Remote Assistant diagnostic capabilities.
CONTRAINDICATIONS
Medtronic pacemakers are contraindicated for the following applications:

Dual chamber atrial pacing in patients with chronic refractory atrial tachyarrhythmias.

Asynchronous pacing in the presence (or likelihood) of competitive paced and intrinsic rhythms.

Unipolar pacing for patients with an implanted cardioverter-defibrillator because it may cause unwanted delivery or inhibition of ICD therapy.

Medtronic.Kappa 400 Series pacemakers are contraindicated for use with epicardial leads and with abdominal implantation.
WARNINGS/PRECAUTIONS
Pacemaker patients should avoid sources of magnetic resonance imaging, diathermy, high sources of radiation, electrosurgical cautery, external defibrillation, lithotripsy, and
radiofrequency ablation to avoid electrical reset of the device, inappropriate sensing and/or therapy.
9462
Operation of the Model 9462 Remote Assistant™ Cardiac Monitor near sources of electromagnetic interference, such as cellular phones, computer monitors, etc. may
adversely affect the performance of this device.
See the appropriate technical manual for detailed information regarding indications, contraindications, warnings, and precautions.
Caution: Federal law (U.S.A.) restricts this device to sale by or on the order of a physician.
Medtronic Leads
For Indications, Contraindications, Warnings, and Precautions for Medtronic Leads, please
refer to the appropriate Leads Technical Manual or call your local Medtronic Representative.
Caution: Federal law restricts this device to sale by or on the order of a Physician.
Note:
This presentation is provided for general educational purposes only and should not be
considered the exclusive source for this type of information. At all times, it is the professional
responsibility of the practitioner to exercise independent clinical judgment in a particular
situation.
Continued in
Basic Pacing Concepts
Parts II and III