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Diagnoses of Cardiac
Arrhythmias Through
Electrocardiographs
Self Tutorial
Greg Haider
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Index
 Importance
of EKG Interpretation
 Review of the Basics
 The Motor of the Cardiovascular System
 The EKG process
– 12-lead ECG
– Printout of a normal rate
 Causes
of Arrhythmias
 Diagnosis of Arrhythmias Using the EKG
 Ethics of EKG Diagnosis
Diagnosis of Cardiac Arrhythmias Through EKGs, By Greg Haider, EE5811 Biomedical Instrumentation
Importance of EKG Interpretation

The underlying motivation and inspiration for
this tutorial lies in the fact that the early
diagnosis of heart arrhythmias will save lives.
Heart Arrhythmias are at fault for the
degradation of thousands of lives. Many of
those affected by these arrhythmias do not
even know that they have them, and therefore,
are not being treated. As the treatment for
heart disease continues to progress, the
diagnosis of the arrhythmias becomes more and
more important. By catching heart arrhythmias
through EKG’s, the lives of thousands of people
can be improved.
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Diagnosis of Cardiac Arrhythmias Through EKGs, By Greg Haider, EE5811 Biomedical Instrumentation
Review of the Basics
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The Heart is
composed of 4
Chambers. Each
having a specific job
in the cardiac cycle
(click on the chart for
more information)
Diagnosis of Cardiac Arrhythmias Through EKGs, By Greg Haider, EE5811 Biomedical Instrumentation
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
Review of the Basics
The Right Atrium
 The Atriums are the gathering
chambers of the heart
 The Right Atrium performs the job of
gathering oxygen depleted blood
from the body.
 Blood becomes oxygen depleted after
nourishing the body, removing carbon
dioxide from capillaries, replacing it with
oxygen

From the Right Atrium, blood is
passed through one of the
atrioventricular valves, the tricuspid,
into the right ventricle.
Diagnosis of Cardiac Arrhythmias Through EKGs, By Greg Haider, EE5811 Biomedical Instrumentation
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
Review of the Basics
The Left Atrium
 The Atriums are the gathering
chambers of the heart
 The Left Atrium performs the job of
gathering oxygen rich blood from the
lungs.
 Oxygen rich blood is used to nourish
the body, removing carbon dioxide from
capillaries, replacing it with oxygen

From the Left Atrium, blood is
passed through one of the
atrioventricular valves, the Mitral
valve, into the left ventricle.
Diagnosis of Cardiac Arrhythmias Through EKGs, By Greg Haider, EE5811 Biomedical Instrumentation
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
Review of the Basics
The Right Ventricle
 The ventricles are the pumping
chambers of the heart
 The Right Ventricle performs the job
of pumping oxygen depleted blood
to lungs


The lungs oxygenate the blood, so that it
can be used again by the body for
nourishing
From the Right Ventricle, blood is
passed through one of the semilunar
valves, the pulmonary valve, into the
pulmonary artery, to the lungs
Diagnosis of Cardiac Arrhythmias Through EKGs, By Greg Haider, EE5811 Biomedical Instrumentation
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
Review of the Basics
The Left Ventricle
 The ventricles are the pumping
chambers of the heart
 The Left Ventricle performs the job
of pumping oxygenated blood to the
body


Oxygenated blood is sent to the body so
that it can nourish the body, removing
carbon dioxide from the capillaries
From the Left Ventricle, blood is
passed through one of the semilunar
valves, the aortic valve, into the
Aorta, to the body
Diagnosis of Cardiac Arrhythmias Through EKGs, By Greg Haider, EE5811 Biomedical Instrumentation
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The Motor of the Cardiovascular
System





Perimeter Layers of the Heart
Characteristics of the
Myocardium
Depolarization/Repolarization
Hearts Pacemakers
Conduction Path
Diagnosis of Cardiac Arrhythmias Through EKGs, By Greg Haider, EE5811 Biomedical Instrumentation
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
The Motor of the Cardiovascular
System
Perimeter Layers of the Heart
– Pericardium and Epicardium
 Outer 2 layers of the heart
 Create a sack to hold pericardial fluid
– Like oil of an engine, the liquid center
creates a frictionless environment for the
heart to pump, minimizing irritation
 Through a fibrous connection, the
epicardium attaches to the myocardium
– Myocardium
 Work Horse of the heart, the muscle
– Endocardium
 Frictionless inner layer, allowing blood to
move as efficient as possible through the
heart and valves
Diagnosis of Cardiac Arrhythmias Through EKGs, By Greg Haider, EE5811 Biomedical Instrumentation
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
The Motor of the Cardiovascular
System
Characteristics of the Myocardium
– The myocardium consists of Myocardial
Cells
 These cells give the myocardium the “fuel” for
pumping
– From these cells, the electrical stimulus in the heart
begin
– The cells branch and interlock such that when one
cell is excited, the adjacent cell is exited, causing a
chain reaction (domino effect)
– The stimulated myocardial cells descend down
the heart, causing the heart to contract and
circulate blood
Diagnosis of Cardiac Arrhythmias Through EKGs, By Greg Haider, EE5811 Biomedical Instrumentation
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
The Motor of the Cardiovascular
System
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Depolarization/Repolarization
– Electrically charged Ions initiate the electrical pulses in the cells
 sodium ions (Na)
 calcium ions (Ca)
 potassium ions (K)
– When at rest (Not Contracted) Myocardial cells are negatively charged,
consisting of internal potassium ions and external sodium and calcium ions
– Depolarization
 Depolarization is the contraction of the heart, caused by fast moving Na ions and
slow moving Ca ions begin to move inward, while K ions move out
– Repolarization
 When releasing, Na ions and Ca ions begin to trade with K ions to the normal
state, this is known as repolarization
– Together, Depolarization and Repolarization create the Action Potential Plot
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Diagnosis of Cardiac Arrhythmias Through EKGs, By Greg Haider, EE5811 Biomedical Instrumentation
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The Motor of the Cardiovascular
System
 Action
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Potential Caused by moving ions in
the myocardial cells
– Phase 0:
 Rapid depolarization of Na ions
– Phase 1 and 2:
 Slow depolarization of Ca ions,
start of repolarization of K ions
– Phase 3:
 Complete repolarization
– Phase 4:
 At rest
Diagnosis of Cardiac Arrhythmias Through EKGs, By Greg Haider, EE5811 Biomedical Instrumentation
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
The Motor of the Cardiovascular
System
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Pacemakers
– nodes of myocardial cells that do not rest, but
continue to depolarize and repolarize at an inherent
rate starting the conduction through the heart
 Sinoatrial Node (SA) – main pace maker
 Automaticiy Foci – Backup pacemakers, pace if a higher
pacemaker fails to beat
– Atrial foci: 60 – 80 bpm
– Junctional foci: 40 – 60 bpm
– Ventricular foci: 20 – 40 bpm
Diagnosis of Cardiac Arrhythmias Through EKGs, By Greg Haider, EE5811 Biomedical Instrumentation
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Conduction Path
•Click on the illustration
for description
Purkinje Fibers
Diagnosis of Cardiac Arrhythmias Through EKGs, By Greg Haider, EE5811 Biomedical Instrumentation
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
Conduction Path
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Start of conduction path
– SA node is located in the upper
right atrium
– This is the main pacemaker of
heart, kick starting the
depolarization of the atriums,
forcing blood into the ventricles
Purkinje Fibers
Diagnosis of Cardiac Arrhythmias Through EKGs, By Greg Haider, EE5811 Biomedical Instrumentation
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Conduction Path
 Atrioventricular
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Node
– The AV node produces a pause in
the electrical flow through the
heart, allowing the atria to
completely contract and fill the
ventricles
Purkinje Fibers
Diagnosis of Cardiac Arrhythmias Through EKGs, By Greg Haider, EE5811 Biomedical Instrumentation
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 His
Conduction Path
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Bundle
– The His Bundle conducts the
depolarization down the septum
into the ventricles and branches
off into the right and left Bundle
Branches
Purkinje Fibers
Diagnosis of Cardiac Arrhythmias Through EKGs, By Greg Haider, EE5811 Biomedical Instrumentation
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Conduction Path
 Purkinje
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Fibers
– These fibers stem off of the right
and left bundle branches into the
myocardium producing a strong
explosion of current, pumping
blood out of the heart
Purkinje Fibers
Diagnosis of Cardiac Arrhythmias Through EKGs, By Greg Haider, EE5811 Biomedical Instrumentation
EKG Measurement
Process

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The 12 lead EKG is the Most common form of EKG Measurement
–
This form of measurement consist so 6 limp leads
6 chest leads

The 6 limb leads are created with electrodes attached to both arms and
the left foot
–
3 Bipolar Limb leads
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3 Augmented Limb leads
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Each lead acts as both anode and cathode
Two leads set as anode, one as the cathode
6 chest leads
–
Positioned along the chest surrounding the heart
–
All chest leads are positively charged, allowing
detection of the hearts electrical activity
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Diagnosis of Cardiac Arrhythmias Through EKGs, By Greg Haider, EE5811 Biomedical Instrumentation
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EKG Measurement
Process

The 12-lead ECG allows the
depolarization and depolarization
of the heart to be detected

Depolarization of the Atrium
produces the P-Wave on the EKG
printout

The complex QRS-Wave of the
printout is produced through
ventricular depolarization

Finally, the EKG’s T-Wave is
produced when the ventricular
repolarizes.
Diagnosis of Cardiac Arrhythmias Through EKGs, By Greg Haider, EE5811 Biomedical Instrumentation
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Causes of Heart Arrhythmias

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Unknown causes
– Too intermittent to diagnose

Weak or lack of connection between Myocardial cells
– Caused by dead tissues or scars, infarctions
 Usually caused by extreme electrical impulses such as a heart attack, also
known as Myocardial Infarction

Chemical Imbalances
– Because the depolarization and repolarization of the heart relies the
movement of ions, and imbalance of these ions can produce abnormal
beats
 Sodium imbalance
 Calcium imbalance

Electrical Confusion
– Again, usually caused by extreme electrical impulses that unsynchronize
the system, sometimes to the point that it is unrecoverable
Diagnosis of Cardiac Arrhythmias Through EKGs, By Greg Haider, EE5811 Biomedical Instrumentation
Diagnosis of Arrhythmias
Using the EKG

Arrhythmias
–
–
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–
–
–
–
–
–
–
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First Degree Heart Block
Second Degree Heart Block
Sinus Rhythm Bradycardia and Tachycardia
Hypercalcemia
Hyperkalemia
Idioventricular Rhythm
Premature Atrial Contraction
Premature Ventricular Contraction
Ventricular Tachycardia
Ventricular Fibrillation
Asystole
Diagnosis of Cardiac Arrhythmias Through EKGs, By Greg Haider, EE5811 Biomedical Instrumentation
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 First
Diagnosis of Arrhythmias
Using the EKG
Degree Heart
Block
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Normal EKG
First Degree Heart Block

First-degree heart block, or first-degree AV block, is the condition under which the electrical
impulse moves through the AV node at a slower rate than normal. The cause of first degree
heart block is not always known since in some cases it can be intermittent. However, in many
cases, it may be to a weakened conduction path caused by minor scarring of the tissue.

The time it takes for the impulse to get from the atria to the ventricles (the PR interval) should
be less than about 0.2 seconds for a normal rhythm. If this time is longer on the EKG, than the
patient under test is experiencing first-degree heart block
Diagnosis of Cardiac Arrhythmias Through EKGs, By Greg Haider, EE5811 Biomedical Instrumentation
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Diagnosis of Arrhythmias
Using the EKG
• Second Degree
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Normal EKG
Heart Block
Second Degree Heart Block

While first degree heart block may cause a physician to take a second look, it is usually not
harmful, producing a valid rate. However, second-degree heart block paints a different picture.
In second-degree heart block, the AV junction moves so slow that some of the electrical
impulses from the atrium never reach the ventricles, meaning scarring is bad enough to
completely disrupt the electrical connection. This behavior will cause the EKG to produce a
double P-wave.
Diagnosis of Cardiac Arrhythmias Through EKGs, By Greg Haider, EE5811 Biomedical Instrumentation
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Diagnosis of Arrhythmias
Using the EKG
• Sinus Rhythm Bradycardia
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Normal EKG
and Tachycardia
Bradycardia
Tachycardia

Sinus Rhythm Bradycardia is the condition in which the patient’s rhythm is under 60 beats per
minute. This condition is usually caused by the SA node firing too slow but could also be a sign
that another atrial foci has taken over pacing due to scarred tissue. However, the blockage of
scar tissue can usually be determined by the characteristics of the P wave, and would not be
classified under this condition. During sinus rhythm bradycardia, the R to R interval is
lengthened, and at times, the P wave is widened.

Sinus Rhythm Tachycardia is the opposite of Bradycardia, in which the internal heart rate is
faster than that of a normal rate. During this condition, the SA node is firing too fast. When a
patient is experiencing Sinus Tachycardia the heart rate of that patient is greater than 100bpm.
Diagnosis of Cardiac Arrhythmias Through EKGs, By Greg Haider, EE5811 Biomedical Instrumentation
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Diagnosis of Arrhythmias
Using the EKG
• Hypercalcemia
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Normal EKG
Hypercalcemia

Hypercalcemia is a condition under which a patient is experiencing high levels of calcium in
his/her body, a chemical imbalance. Because calcium plays such an important role in the
behavior of the heart, excess calcium can cause it to perform abnormally. With too much
calcium, the interval between the final depolarization phase caused by calcium ions and the
repolarization phase is shortened. The effects of Hypercalcemia are very difficult to see in
some patients, however with a high enough content, the calcium can affect the heart such that
the S-T interval is visibly shortened, or even invisible.
Diagnosis of Cardiac Arrhythmias Through EKGs, By Greg Haider, EE5811 Biomedical Instrumentation
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Diagnosis of Arrhythmias
Using the EKG
• Hyperkalemia
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Normal EKG
Hyperkalemia

Hyperkalemia is the excessive amount of potassium in the body. Again, like Calcium, Potassium
is an important ion in the heart, affecting the behaviors of the hearts depolarization. Therefore,
large amounts of potassium in a patient’s body will affect the EKG. When large amounts of
Potassium are found in the body, the T-wave takes on a tent shaped form. As with
Hypercalcemia, Hyperkalemia is a very difficult condition to diagnose using an EKG printout due
to the small effects that are produced with the additional Ions.
Diagnosis of Cardiac Arrhythmias Through EKGs, By Greg Haider, EE5811 Biomedical Instrumentation
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Diagnosis of Arrhythmias
Using the EKG
• Idioventricular
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Normal EKG
Rhythm
Idioventricular Rhythm

When one the ectopic foci, located at or above the atrioventricular node, fails to discharge,
usually due to infracted tissue, atrial contraction never occurs. When one of these foci fails to
fire, a foci node within the ventricle will takeover, producing ventricular depolarization and
repolarization. With the loss of Atrial contraction, the P-wave is absent from the EKG, showing
only the QRS complex. Also, because the pacemaker is located in the ventricle, the QRS wave
takes on a much different rate than that seen on a normal EKG. Because a separate
automaticity foci is controlling the rate, the rates of Idioventricular Rhythms are very slow –
usually 30 to 40 beats per minute.
Diagnosis of Cardiac Arrhythmias Through EKGs, By Greg Haider, EE5811 Biomedical Instrumentation
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Diagnosis of Arrhythmias
Using the EKG
• Premature Atrial
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Normal EKG
Contraction
Premature Atrial Contraction

In many cases, physicians are unable to determine the cause of Premature Atrial Contraction
(PAC), however the signs of this condition are obvious on the EKG. In PAC, an SA node kicks
off atrial contraction soon after ventricular repolarization, producing a strange T-P interval from
one beat to the next. The heart rate usually picks up as normal, but with a shift in phase.
Diagnosis of Cardiac Arrhythmias Through EKGs, By Greg Haider, EE5811 Biomedical Instrumentation
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Diagnosis of Arrhythmias
Using the EKG
• Premature Ventricular
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Normal EKG
Contraction
Premature Ventricular Contraction

Premature Ventricular Contraction is the escape of a ventricular automaticity foci pace, while
the SA or other ectopic foci are performing their duties correctly; there is no block that makes it
necessary for this foci to fire. In this case, the ventricle contracts before the atrial pacemaker
has an opportunity to initiate the normal rate. Therefore, this condition is seen on the EKG as a
missed P-wave, and an irregular, widened QRS complex.
Diagnosis of Cardiac Arrhythmias Through EKGs, By Greg Haider, EE5811 Biomedical Instrumentation
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Diagnosis of Arrhythmias
Using the EKG
• Ventricular
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Normal EKG
Tachycardia
Ventricular Tachycardia

Ventricular tachycardia is defined as three or more beats of ventricular origin in succession at a
rate greater than 100 beats per minute. There are no normal-looking QRS complexes and the
rhythm is usually regular, but on occasion it may be modestly irregular. Much like PVC, under
the condition of ventricular tachycardia, the SA is still depolarizing the atria, however in
ventricular tachycardia a ventricular foci node is controlling the pace at a rate faster or equal to
that of the atria. Because the ventricle is in refractory when the atria depolarization is passed
to the atrioventricular node, this stimulus has no effect on the synching the two rates. The
ventricular depolarization far outweighs the atria depolarization, dominating the EKG screen.
Diagnosis of Cardiac Arrhythmias Through EKGs, By Greg Haider, EE5811 Biomedical Instrumentation
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Diagnosis of Arrhythmias
Using the EKG
• Ventricular
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Normal EKG
Fibrillation
Ventricular Fibrillation

Ventricular fibrillation is caused by the total disorder of ventricular foci. This condition is caused
by extreme electrical stress in the heart, scrambling the rhythm of the heart. Under these
conditions, the ventricle is attempting to contract at different rates, at different locations. This
chaotic depolarization results in a ventricular fibrillation, or a quiver, rather than a rhythm,
resulting in very little blood flow from the heart. Ventricular fibrillation is shown on the EKG as
very small, random pulses.
Diagnosis of Cardiac Arrhythmias Through EKGs, By Greg Haider, EE5811 Biomedical Instrumentation
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Diagnosis of Arrhythmias
Using the EKG
• Asystole
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Normal EKG
Asystole

The simplest EKG reading to determine is that of Asystole, or death. At the time of Asystole,
the heart is fully depolarized, in both the atrial and the ventricular, with no attempts to
repolarize. Because there is no electrical activity in the heart, there is no EKG surge caused by
the lead connections. The EKG reading is just what one would expect under these conditions,
flat.
Diagnosis of Cardiac Arrhythmias Through EKGs, By Greg Haider, EE5811 Biomedical Instrumentation
Medical Ethics of
EKG Diagnosis
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 The
EKG process itself appears harmless,
however every procedure involves an
ethical decision
– Ethical Question:
 Is it necessary?
– May Cause Physical Discomfort
 Leads must be attached to the body
 May Cause Mental Discomfort
– Embarrassment
– Fear
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Diagnosis of Cardiac Arrhythmias Through EKGs, By Greg Haider, EE5811 Biomedical Instrumentation
Medical Ethics of
EKG Diagnosis
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
Ethics of treating arrhythmias following a Diagnosis
–
Comfort

–
–
Drug treatment versus possible implantable device
Life Circumstances

Will this require monthly checkups?
–
–
Single parent
Traveling position
–
Fear of hospitals
Age

Elderly
–

–
Would surgery produce more risk than the condition itself?
Young
–
Because patient is still growing, should other alternative treatment be decided on if an implantable is the usual treatment?
Finances




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Is the patient insured?
Will the patient be retiring, will they keep insurance?
Many heart conditions are chronic, therefore the treatment will be with them forever, can they not only afford
it now, but what about 10, 20, or even 50 years down the road
Each decision must be made on a patient to patient bases
–
The best treatment is not always the right treatment

Do good versus Do right
Diagnosis of Cardiac Arrhythmias Through EKGs, By Greg Haider, EE5811 Biomedical Instrumentation