Basic Pacing Concepts Part I

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Basic Pacing ConceptsPart I
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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

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Pacing Systems
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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

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During Conduction, an Impulse Begins in the
Sinoatrial (SA) Node and Causes the Atria to
Contract
Atria
Sinoatrial (SA) Node
Ventricles
Atrioventricular (AV) Node
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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
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Diseased Heart Tissue May

• Prevent impulse generation in the SA node
• Inhibit impulse conduction

SA node
AV node
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Implantable Pacemaker Systems Contain the
Following Components

Lead wire(s)
Implantable pulse generator (IPG)
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Pacemaker Components Combine with Body Tissue to
Form a Complete Circuit

• Pulse generator power source or battery
• Leads or wires
• Cathode (negative electrode)
• Anode (positive electrode)
• Body tissue

Lead
IPG
Anode
Cathode
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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
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Leads Are Insulated Wires That

• Deliver electrical impulses from the pulse
  generator to the heart
• Sense cardiac depolarization

Lead
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Types of Leads

• Endocardial or transvenous leads
• Myocardial/Epicardial leads

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Transvenous Leads Have Different Fixation
Mechanisms

• Passive fixation
• The tines become lodged in the trabeculae(fibrous
  meshwork) of the heart

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Transvenous Leads

• Active Fixation
• The helix (or screw) extends into the endocardial
  tissue
• Allows for lead positioning anywhere in the
  hearts chamber

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Myocardial and Epicardial Leads

• Leads applied directly to the heart
• Fixation mechanisms include
• Epicardial stab-in
• Myocardial screw-in
• Suture-on

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Cathode

• An electrode that is in contact with the heart
  tissue
• Negatively charged when electrical current is
  flowing

Cathode
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Anode

• An electrode that receives the electrical impulse
  after depolarization of cardiac tissue
• Positively charged when electrical current is
  flowing

Anode
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Conduction Pathways

• Body tissues and fluids are part of the
  conduction pathway between the anode and cathode

Anode
Tissue
Cathode
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During Pacing, the Impulse


Impulse onset

• Begins in the pulse generator
• Flows through the lead and the cathode ()
• Stimulates the heart
• Returns to the anode ()

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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
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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
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Unipolar and Bipolar Leads
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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

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Bipolar leads

• Bipolar leads are less susceptible to oversensing
  noncardiac signals (myopotentials and EMI)

Coaxial Lead Design
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Lead Insulation May Be Silicone or Polyurethane
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Advantages of Silicone-Insulated Leads

• Inert
• Biocompatible
• Biostable
• Repairable with medical adhesive
• Historically very reliable

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Advantages ofPolyurethane-Insulated Leads

• Biocompatible
• High tear strength
• Low friction coefficient
• Smaller lead diameter

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A Brief History of Pacemakers
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Single-Chamber and Dual-Chamber Pacing Systems
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Single-Chamber System

• The pacing lead is implanted in the atrium or
  ventricle, depending on the chamber to be paced
  and sensed

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Paced Rhythm Recognition
AAI / 60
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Paced Rhythm Recognition
VVI / 60
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Advantages and Disadvantages of Single-Chamber
Pacing Systems
Disadvantages
Advantages

• Single ventricular lead does not provide AV
  synchrony
• Single atrial lead does not provide ventricular
  backup if A-to-V conduction is lost

• Implantation of a single lead

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Dual-Chamber Systems Have Two Leads

• One lead implanted in the atrium
• One lead implanted in the ventricle

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Paced Rhythm Recognition
DDD / 60 / 120
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Paced Rhythm Recognition
DDD / 60 / 120
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Paced Rhythm Recognition
DDD / 60 / 120
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Paced Rhythm Recognition
DDD / 60 / 120
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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

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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 Medtro
nic 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 Operati
on 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.
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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.
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Continued inBasic Pacing ConceptsParts II and
III