Download Pacemaker

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
Permanent Pacemaker Device
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