Download Artificial Pacemakers - McMaster University > ECE

Cardiac Pacemakers
Aishwarya Sreenath
Naheed Baksh
Presentation Outline
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History of pacemaker
Anatomy of the heart
Natural pacemaker
Hemodynamics of heart
Types of artificial pacing
Basics structure, materials and power supply
Types of permanent pacemaker
When are pacemaker prescribed
Hemodynamic effects of cardiac pacemakers
Example: Stokes Adams Syndrome
Implementation and implementation risks
Future
History of Artificial Pacemakers
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Since the beginning of the eighteenth
century, physicians and scientist knew
that heart is just a muscle and it can be
contracted by electrical simulation.
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Re-animation chair, “FRANKENSTEIN”
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1932 American physiologist Albert
Hyman invented an electro-mechanical
instrument, and he named it “artificial
pacemaker”
First human pacemaker, Made In Canada
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1950, Canadian Electrical Engineer John Hopps and surgeon
Wilfred Gordon Bigelow designed the first pacemaker to be
used on patients in Toronto General Hospital.
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John Hopps was the founding president of the Canadian
Medical and Biological Engineering Society
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A Transcutaneous pacemaker
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Painful for the patient
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Used the AC wall sockets there was a potential risk of
electrocution.
PM – 65
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Early 1950, Paul Zoll
Both electrocardiograph and
electrical pulse generator.
Pace the heart from external
device.
Also Transcutaneous
Uncomfortable
Limitations in movement
Acceptable as long as the
pacemaker was considered
emergency apparatus for postsurgical care
First implantable pacemaker
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Dr. C. Walton Lillehei encountered a power failure and thus
realized that a pacemaker should be a compact device that
runs on batteries.
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Earl Bakken upon Dr. Lillehei’s request, designed a prototype
that ran on batteries.
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Engineer Rune Elmqvist and Dr. Ake Senning created the first
implantable pacemaker and successfully implanted in a patient
on October of 1958.
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After that all the developments are based on the implantable
pacemaker model.
Further Developments
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1975 - Lithium-iodine batteries took battery life from
months to years
mid-1970s, pacemaker settings could be
programmed using radio-frequency signals.
1980’s rate responsive pacing
In the late 1990's, pacemakers could mimic the
heart's natural rhythm even more closely by
adjusting the rhythm according to a person's activity
level.
Basic heart Structure
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Blood flow
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Conduction System
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Autorhythmic fibers are specialized cardiac muscle cells that
cause an inherent and rhythmical electrical activity in the heart
Autorhythmic fibers are self excitable- they simulate contraction
without a requisite electrical impulse from the central nervous
system
A single cardiac muscle cell can contact rhythmically at a steady
rate without any input
If two cardiac muscle cells are in contact, the one that contracts
first will simulate the other to contract
The contractile activity is regulated by the autonomic nervous
system
Cardiac muscle cells are connected to each other through
intercalated discs which support synchronized contraction of the
cardiac tissue
Intercalated discs
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Intercalated discs conduct electrochemical potentials between the
cytoplasms of adjacent cells through gap junctions
Cardiac Action Potential Propagation
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Pathway of AP
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Hemodynamics of heart
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EDV (END DIASTOLIC VOLUME)
ESV (END SYSTOLIC VOLUME)
Stroke Volume, SV = EDV – ESV
Generally SV = 70 ml/beat
HR = heart rate = 75 beats/min
CO = HR x SV
CO = 5250 ml/min (5.25 L/min)
Types of artificial pacing
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Percussive Pacing
Transcutaneous Pacing
Transvenous Pacing
Permanent pacing
Percussive Pacing
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Strike from a distance
of 20-30 cm with closed
fist on the left lower
edge of sternum.
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The pressure in the
ventricle should rise 1015 mm hg.
Transcutaneous pacing
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External method
Emergency option
Two pads are placed on the
patient
Starting with low current the
pacemaker is set to the
optimal current
Not a comfortable procedure
Transvenous Pacing
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Bridge to permanent
pacemaker placement
A sterilized wire is
placed in a vein and
carried to an atrium or
ventricle.
The wire is attached to
an external pacemaker
Permanent Pacing
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Implanted device similar to transvenous
pacemaker
Powered by battery that runs for 6-12 years.
2 components
1) Pulse generator
2) Insulated lead(s) and electrodes.
What is an artificial pacemaker?
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A pacemaker is an electronic device
implanted in the body to regulate the heart
beat.
A Pacemaker is not designed to defibrillate
the heart by delivery of shocks.
The PM delivers electrical stimuli over leads
with electrodes in contact with the heart.
Basic structure of pacemaker
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Pulse generator can be both
rate responsive or fixed rate
Pacing leads are passed
through a vein (in this case
SVC)
Then the electrodes are
placed on the myocardium
of the desirable location
Figure: Atrioventricular
pacemaker
Materials used in Pacemaker
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Qualities for the materials used in the pacemaker:
Lowest stimulation voltage
– Possible long term implementation
– Biocompatibility and nontoxicity
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Stainless steel electrodes are replaced by cobalt
alloys, platinum-iridium alloys.
Carbon is also being used to some extent.
Stainless steel is still the most cost efficient
Pulse generator is housed in a titanium container
Power supply
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Mercury-zinc battery – 48-60 months
Lithium Iodide battery – 10+ years
Biothermal Batteries (Under progress)
Types of permanent pacemakers
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Single-Chamber Pacemakers
Dual-Chamber Pacemakers
Single Chambered Pacemaker
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One wire is placed on the
heart chamber
Either Atrium or the Ventricle
Figure: Single chamber
ventricular pacemaker
Generally fixed rate
$2,500.00 cheaper from dual
chambered but similar
efficiency in many cases.
Dual Chamber Pacemaker
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Two leads are placed in two
different chambers of heart
Generally one lead goes to
a ventricle and the other
goes into the atrium
This approach more closely
matches the natural pacing
of the heart
40% of the pacemakers
used in Canada are dual
chamber.
Types of pacemaker
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Fixed rate pacemakers
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Rate responsive pacemaker
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set to work at a certain heart rate
If the heart’s own intrinsic rate dropped below a
pre-set number the pacemaker would begin to
pace at a preset rate.
Determines what the heart rate should be from
moment to moment
Rate Responsive Pacemaker
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Technological advancements
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The more the patient’s body is moving the
faster the heart rate should be.
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2 major mode to detect the optimal cardiac
output
– Activity sensor
– Breathing sensor
When are pacemakers prescribed?
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Bradycardia
Fibrilation
Heart failure
Syncope
Quiz
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What is Cardiac Output?
Hemodynamic effects and issues
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Cardiac output decreases with many heart problems.
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CO = HR x SV
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The low CO is augmented when HR is increased by using the
artificial pacemaker.
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CO increases with the increment of rate until a maximum level
of CO is reached.
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Optimal rate = maximum cardiac output
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This maximum level is very close to the CO in people with no
heart trouble.
Frank-Starling Law Of The Heart
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The greater the heart
muscle is stretched
during the filling, the
greater the quantity of
blood pumped.
Hemodynamic effects and issues
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When CO is maximum, increase in heart rate
decreases the stroke volume.
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Thus, if artificial pacemaker is applied to a
normal heart, no significant change in
cardiac output will be observed.
Stokes Adams Syndrome example
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Heart temporarily loses
connection between
atria and ventricles.
Temporary heart block
causing bradycardia.
Brain does not get
enough oxygen rich
blood.
Syncope (faint) and
seizure
Causes
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Heart diseases that affect the AV node.
Surgical trauma
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Repair of a heart defect
Replacement of valves
Cardiomyopathies
Myocarditis
Medication
Diagnosis
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Electrocardiogram
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Echocardiogram
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Biopsy
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Cardiac catheterization
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Electrophysiological
study
Treatment
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Depending on the
cause.
Discontinuation of
medication
Pacemakers are used
in severe cases.
AV block
One electrode is placed
on the atrium and the
other on the ventricle.
Implementation
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Pacemaker surgery is done under local anesthesia.
A small incision is made where the pacemaker will be located.
The leads are guided through a large vein to the heart.
The pulse generator is then placed under the skin and then the
incision is closed.
Approximately 1 hour long
Regular monitoring of BP and HR might be needed.
The incision spot should not be wet for 10 days.
Minor pain and discomfort might occur for 5 – 10 days.
Risk of implementation
Implantation of the pacemaker is a safe procedure. Procedural
complications are rare. These include but are not limited to:
z 5% chance of bleeding or severe bruising at the insertion site.
z 1% chance of lung puncture while obtaining access into the
veins.
z 1% chance of puncture of heart muscle. This may require
specific treatment
z 1% chance of infection
z Other risks may apply, depending upon the patients medical
condition
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Future of Cardiac Pacemakers
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Biothermal Batteries
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Transtelephonic monitoring
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Already exists
Improving to a cellphone-like device
In body communication system
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Converts body’s own heat into electricity
ZL70100 ultra low-power transceiver chip
transceiver in a pacemaker can wirelessly send
patient health and device performance data to a
bedside base station.
500 kb/s data transmission over a typical two-meter
range.
This is already made and should be in the market
anytime.
Any Question?
Thank you for your attention
References
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Harold Siddong and Edgar Sowton, “Cardiac pacemakers”, Charles C Thomas Publisher
L.A. Geddes, “Cardiovascular Devices and Their Applications”, Ed. 10, Wiley-Interscience
Publication
Dr. Richard Sutton and Dr. Ivan Bourgeois “The foundation of Cardiac Pacing, Pt.1”, Futura
Publishing Company. Vol 1, 1991
Heinemann, William, Fontaine. G, Grosgogeat.Y, and Welti. J.V.T. “The Essentials of cardiac
pacing”. France: Cedig Publisher, 1976.
H.J. Th. Thalen, Jw.van den Burg, J.N Homan can der Heide, and J, Nieveen. “The Artificial Cardiac
Pacemaker”. The Netherlands: London Royal VanGorcum Publishers, 1969.
Gerrard J. Tortora, Derrickson, Bryan. “Principles of Anatomy and Physiology”. United States of
America: John Wiley & Sons, Inc, 2006.
http://www.howstuffworks.com/heart.htm
http://www.nlm.nih.gov/medlineplus/tutorials/pacemakers/htm/index.htm
http://heartdisease.about.com/cs/arrhythmias/a/pacemakers.htm
http://www.uvka.de/univerlag/volltexte/2005/77/pdf/Oertel_Modelling_the_human_cardiac_fluid.pdf
http://www.emedicine.com/emerg/topic699.htm
http://www.emedicine.com/med/topic189.htm
http://www.medicinenet.com/pacemaker/article.htm
http://www.thebakken.org/artifacts/pacemakers.htm
http://www.sdrs.org/equipment-als.htm
http://www.cardiocare.co.za/courses.php
References (Cont’d)
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http://www.chw.org/display/displayFile.asp?filename=/Groups/Pediatri
cHealthInformation/CardiovascularDisorders/pacemk10.jpg
http://fhs.mcmaster.ca/main/news/news_archives/pace.htm
http://heart.health.ivillage.com/arrhythmia/stokes-adams.cfm
http://www.londonafcentre.co.uk/images/pacemaker.gif
http://www.chw.org/display/displayFile.asp?filename=/Groups/Pe
diatricHealthInformation/CardiovascularDisorders/pacemk9.jpg
http://www.cardioassoc.com/patient_pgs/procedures/pacemaker.asp
http://en.wikipedia.org/wiki/Artificial_pacemaker
http://www.medicineonline.com/reference/Computers/info/Pacemaker.
htm
http://en.wikipedia.org/wiki/Cardiac_pacemaker
http://en.wikipedia.org/wiki/Cardiac_muscle