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ARTIFICIAL PACEMAKERS: WHY WE NEED THEM TO BE COMPATIBLE
WITH MRI
Daniel Mercader (dlm85@pitt.edu)
THE PACEMAKER: THE AUTOMATIC
TIME KEEPER
The pacemaker, or sinoatrial node, is responsible for
controlling heart rate. When it does not function properly,
the heart can suffer from arrhythmias such as bradycardia
(heart pumps too slow), tachycardia (heart pumps too fast),
or irregular heartbeats. The most common way of taking
care of these conditions is by use of an artificial pacemaker
that is planted on the heart. Although artificial pacemakers
have proven effective in controlling heart rate, one of the
major problems in their implementation is the increase in
danger of undergoing an MRI (magnetic resonance imaging)
scan. MRI scans are very important in diagnosing many
patients because they allow professionals to analyze internal
organs, blood vessels, muscles, joints, and areas of infection
without the use of x-rays, which subject a patient to ionizing
radiation, or surgery, which comes with a physical risk. [1]
A solution to this problem comes in the form of artificial
pacemakers that can undergo the conditions of an MRI
without any of the harmful side effects such as the device
shifting, heating up, or malfunctioning. I think it is important
that all artificial pacemakers can endure an MRI because one
study has shown that 75% of people who receive an artificial
pacemaker will one day need an MRI. [1] The technology
exists to allow pacemakers to contain less magnetic material,
to protect their internal circuits, and to minimize the
warming in the leads.
The research and development of any medical device is
affected by the codes of ethics that exist for engineers in
general, and more specifically, biomedical engineers. The
engineering code of ethics is significant because it helps
engineers to avoid possible mistakes that arise and aids in
decision making about risks that could affect the safety of
the public. It is important for engineering ethics to be
analyzed in this situation because devices that interact with
the heart always have a safety concern. The NSPE (National
Society of Professional Engineers) code of ethics states that
“Engineers are encouraged to…work for the advancement of
the safety, health, and well-being of their community.” [2]
This issue about artificial pacemakers is something that
intrigues me because my father has had an artificial
pacemaker for seven years. He had a myocardial infarction
when I was in sixth grade which damaged some of his
cardiac tissue. I have seen him go through the pat-down line
at airports because the security devices use magnetic
University of Pittsburgh, Swanson School of Engineering 1
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imaging which may interfere with his artificial pacemaker.
Because it is something so personal, it gives me motivation
as an engineer-to-be to attempt to solve medical problems
such as this.
The last part of this paper is going to assess the value of
researching and writing a paper such as this. In order to be
an engineer it is important to understand exactly what
studying to gain an engineering degree and physically
practicing engineering encompasses. Writing a paper about
an interest topic and analyzing the ethics and education
purposes helps to strengthen the overall skills of an engineer.
HOW ARTIFICIAL PACEMAKERS AND
MRI SCANS FUNCTION
Pacemakers
The sinoatrial node is a group of cells located in the
hearts right atrium. They send out an electrical signal which
causes the atria to contract. The impulse travels to the
atrioventricular node and once it is received, it delays for
about one tenth of a second then sends out a signal for the
ventricles to contract in order to keep blood flow running
smooth. This process happens about sixty to eighty times a
minute which is standard heart rate. [3] An artificial
pacemaker works in a very similar way to this process. The
implanted pacemaker can send out an electrical impulse
similar to the one a natural pacemaker sends out by attaching
two leads into the heart. It can control the impulses sent out
per minute with a computer chip and circuitry.
Daniel Mercader
THE SINOATRIAL NODE AND THE
ATRIOVENTRICULAR NODE IN THE HEART
This figure shows the placement of the nodes that act as
the pacemaker in relation to the heart. [4]
MRI Scans
Magnetic Resonance Imaging plays an important role in
diagnosis and treatment because it can give an accurate
image of soft tissue without the use of surgery. 30 million
MRI scans are conducted annually. [5] MRI scanners work
because a strong magnetic field is produced from sending an
electrical current through a large, wired loop. At the same
time this magnetic field is being formed, other coils send
radio waves into the substance being scanned. This causes
the protons in the substance to align, which in turn causes
the molecules to excite and release energy. This energy is
picked up by receivers in the machine and a computer is able
to produce a three dimensional image of what is being
scanned. [6]
INTERFERENCE BETWEEN
ARTIFICIAL PACEMAKERS AND MRI
SCANS
Annually, 200,000 patients cannot receive and MRI
because of artificial pacemakers. Since MRI scanners can
omit a magnetic field of up to 3 Tesla, parts of the
pacemaker which are metallic and magnetic could possibly
shift leading to complications. Even if nothing shifts, the
magnetic field can confuse the circuitry on the implanted
pacemaker and cause it to malfunction/misfire. [7]
Malfunctions or misfires in pacemakers can be very
dangerous because it directly affects the heart rate. A person
can be physically affected if the heart is not pumping
properly because oxygen may not get to the necessary areas
or it may not be getting there fast enough.
The other way an MRI scanner can affect a pacemaker is
through thermal induction. “The electrode leads can function
as an antenna, in which the energy that is generated by
variable magnetic fields is conducted to the adjacent tissue
in the form of heat”. [4] The heating of the leads can lead to
scarring of the cardiac tissue, and cardiac tissue does not
regenerate which leads to an all-around weaker heart.
MAGNETIC FIELDS AFFECTING A PACEMAKER
This figure shows the three factors that mess up a
pacemakers. The first is a static magnetic field. The second
is switching the magnetic fields quickly. Third is the HF
impulses (or the impulses that cause the leads to heat up) [7]
NEW TECHNOLOGIES
An analysis of a device called the Revo MRI Surescan
pacing system helps to show how important it is that people
who are implanted with artificial pacemakers are able to
undergo an MRI scan if necessary. This device contains
several key pieces of technology which all new pacemakers
should consider using.
The first is the Surescan® system the device contains.
This technology can be activated before a patient goes into
an MRI environment and ensures their safety. It allows for a
lower level of activity within the device for the time the
patient needs to be in the MRI machine. This also means
ensuring the leads do not heat up to a dangerous
temperature. In a study done with patients who have
pacemakers with this technology, no complications were
found within 464 people who had an MRI done. [7]
Another key feature is the rate response system. This
system allows the pacemaker to adapt to an increase or a
decrease in physical activity by adjusting the rate at which it
sends out impulses. This could be helpful in the case of an
MRI because of the anxiety a patient may feel when being in
its enclosed space or waiting to find out a diagnosis.
A final important technology is the “cardiac compass”.
This aspect of the device allows for data over the last
fourteen months to be recorded and analyzed. It can show
when complications within the heart have occurred and
professionals can make decisions based on that data.
ETHICS: WORKING TO KEEP
ENGINEERS ON THE RIGHT TRACK
It is of the utmost importance that engineers adhere to the
canons stated in the codes of ethics that apply to them. I use
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Daniel Mercader
the word important because the application of the
technologies that they develop will directly affect people.
Many of the tenets in both the NSPE and BMES
(Biomedical Engineering Society) are directed toward
engineers holding the safety and comfort of the community
in high regard. The BMES code of ethics openly states
“Biomedical engineers in the fulfillment of their professional
engineering duties shall use their knowledge, skills, and
abilities to enhance the safety, health, and welfare of the
public.” [8] This declaration connects the main purpose of
this paper to ethics because the developers of the
technologies discussed have worked to improve the quality
of life for recipients of artificial pacemakers. The fact that
the developers worked for the safety of patients and that they
“considered the broader consequence of their work” [8] by
coming up to a solution for one of the common side effects
only strengthens my position of making artificial
pacemakers MRI compatible.
Not only does following a code of ethics lead to more a
greater safety for more people, but it also guides engineers in
the decision making they encounter on a daily basis. Solving
the types of problems that engineers attack comes with a risk
assessment more often than not. This process is facilitated
by listening to the code of ethics which serves as a way to
protect many parts of humanity while making progress.
WHY THE INTEREST IN
PACEMAKERS?
My interest in making pacemakers that are compatible
with MRI scanning arose from two sources. The first reason
was growing up watching my father deal with the
complications that come along with a pacemaker. Knowing
that one simple machine helps his heart function is a cause
for worry. The possibility of a malfunction, and ultimately a
life-threatening situation, led me to research one of the
possible causes of artificial pacemaker failure and the
possible solutions to that problem.
Along with my father, I also researched this topic
because I plan to major in biomedical engineering. The first
time I encountered biomedical engineering I knew that it
would be my course of study. The topics that it covers
coincide with my interests of the human body, math, and
medical technology. I was able to research an area I might
one day see again because I am fascinated with how
mechanical devices can keep a human alive and help
improve a quality of life. Biomedical engineers help create
these devices and the field is ever expanding.
THE EDUCATIONAL BENEFITS OF A
RESEARCH PAPER
There is an excellent educational value in researching
and writing about the advantages of the advancement in
pacemaker safety and compatibility with MRI scanners is
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necessary. Sometime in the future, it is very likely that many
engineers will do some form of their own scientific research.
If an engineer has never had any background in writing a
paper then the task of relaying their data in a presentable
format will be a very difficult task.
This writing assignment also calls attention to the types
of issues that engineers-to-be will deal with in the future.
“Although students are usually hindered by an incomplete
knowledge and experience base, writing assignments still
provide one of the best means of developing student
awareness of the nontechnical issues that are central to
engineering practice.” [9] This excerpt from an article
discussing the use of writing assignments in engineering
courses demonstrates why writing papers about an interest
topic to hone the skillset of research and presenting
information.
Lastly, there is educational value in studying the codes of
ethics that all engineers are subjected to. Being exposed to
them early on helps to reinforce the concepts discussed
about in them. This is valuable for engineers because it gives
them an idea of the way they will be thinking and how they
will be encouraged to go about problem solving in a way
that is beneficial to society. Thus this paper serves as a way
not only to research a scientific topic but also learn what
being an engineer entails in its entirety.
HEART PROBLEMS WILL STILL EXIST
IN THE FUTURE
In conclusion, it is important to see the information
presented in terms of paving the way for a better future.
Technologies such as SureScan® are essential to the wellbeing of mankind because then more people will be able to
get the medical tests that could save their lives. It is
important for technology to be compatible in order to reap
the benefits from all that is available. It is the job of a
biomedical engineering to find ways to sustain a lifestyle
that can be enhanced through medical devices. This concept
is developed especially through an analysis of the code of
ethics for engineers. Along with a look of the ethics of this
problem and possible solution, there are benefits of writing
this paper and doing the research required for it. A paper like
this should be required be instilled into engineering
programs at other schools because of how efficiently it
teaches many aspects of being an engineer.
Specifically for this topic, heart problems are not going
to go away, but there will be treatment available to either
cure or hinder some of the horrific effects. Pacemakers are
an acceptable way to treat for arrhythmias, but there is a
possibility that a patient may need an MRI. Thanks to
advances in how pacemakers are manufactured, patients will
be able to be saved from further harm.
REFERENCES
Daniel Mercader
[1] (2012). “Revo SureScan Pacing System.” Medtronic
Inc. [Online Article]
http://www.medtronic.com/patients/bradycardia/device/ourpacemakers/revo-mri-surescan/index.htm
[2] (2012) “NSPE Code of Ethics for Engineers.” NSPE.
[Online Code]
http://www.nspe.org/Ethics/CodeofEthics/index.html
[3] J. Layton. (2012). “What determine the rhythm of
your heart?” Discovery Communications, LLC. [Online
article] http://health.howstuffworks.com/humanbody/systems/circulatory/heart-rhythm1.htm
[4] (2012). “Definition of SA Node.” [Picture]
http://drugline.org/medic/term/sa-node/
[5] (2010, May 22) “Revo MRI SureScan Pacing System
safe in MRI systems” Medical Physics Web. [Online Blog].
http://medicalphysicsweb.org/cws/article/newsfeed/42049
[6] M. Kalapurayil. (2009, April 16). “What is MRI?
How does MRI work?” Medical News Today. [Online
Article]
http://www.medicalnewstoday.com/articles/146309.php
[7] H. Bovenschulte M.D, K. Schulter-Brust M.D, T.
Liebig M.D, et al. (2012, April 12). “MRI in Patients With
Pacemakers.” Deutsches Artzeblatt International. [Journal
Article Online]
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3345344/
[8] (2012) “Biomedical Engineering Society Code of
Ethics.” BMES. [Online Code]
http://www.bmes.org/aws/BMES/asset_manager/get_file/39
579/bmes_code_of_ethics.pdf?ver=1535
[9] R.W. Day, M. Kuhn, K. Vaught-Alexander. (1996,
January 1). “Context for Writing in Engineering
Curriculum.” Journal of Professional Issues in Engineering
Education and Practice. [Journal Article Online]
http://web.ebscohost.com/ehost/pdfviewer/pdfviewer?sid=d8
a2955c-038f-4088-a9a5821d01f40766%40sessionmgr115&vid=2&hid=118
ADDITIONAL SOURCES
(2012) “Arrhythmias.” A.D.A.M Medical Encyclopedia.
[Online Encyclopedia Article]
http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0002091/
ACKNOWLEDGEMENTS
I would like to thank Stephen Klein for helping me stay
on task to write this paper. I also would like to thank Shruti
Vemputi for discussing possible topics with me which led
me to find this topic. I would also like to thank my high
school English teacher, Mr. Christopher Holwick, and
friend, Joel Roggeman, for making some suggestions to
change my paper.
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