1 Cardiac Pacemaker By: Ziqi (Hugo) Wang and Garret McConville
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Cardiac Pacemaker
By: Ziqi
(Hugo) Wang and Garret McConville
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Overview
• Heart Beat• Abnormalities in Heart Beat
• Cardiac Pacemaker
• How pacemaker works
• Case Study • The surgical procedure• Future of pacemakers
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The Heart
The Basics:4 Chambers:‐Right Atrium‐Right Ventricle‐Left Atrium‐Left Ventricle
Heart ValvesInput VeinsOutput Arteries
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Blood Flow In the Heart
• Blood flows‐Vena cava‐Right atrium‐Right ventricle‐Pulmonary artery‐Left atrium‐Left ventricle‐Aorta
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Heart Beat
• Normal heart beat is 50‐70 times per minute
• At times it can beat faster tachycardia (sports) or slower bradycardia
(sleep)
• An abnormal heart beat is called an arrhythmia
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How do we generate a Heart Beat
• Rhythmic heart beat caused by electrical activity
• In heart you have autorhythmic
fibers
• These fibers act as pacemaker and conductive system for the heart by generating action
potentials
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Action Potential Through the Heart
• Begin at SA node
• Reaches the AV node
• Enters the AV node
• Enters the right and left bundle
branches
• Arrives at Purkinje fibers
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Electrocardiogram(ECG)
• Action potentials generate electrical currents
recorded to create ECG
• P is atrial
depolarization
• QRS is rapid ventricular depolarization
• T is ventricular repolarization
• By comparing a normal ECG to that of a
patients a doctor can predict abnormalities
within the heart
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Heart Beat Abnormalities
• Called an arrythmia
• Two categories supraventricular
and ventricular arrythmias
Supraventricular Ventricular
Premature atrial
contraction Premature ventricular
complex
Supraventricular
tachycardia Ventricular tachycardia
Sick sinus syndrome Ventricular fibrillation
Atrial
fibrillation
Atrial
flutter
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Causes of Arrythmias
• Infection or fever• Physical or emotional Stress
• Disease such as anemia or thyroid disease
• Drugs• Inherited
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Symptoms
• Palpitations (skipped beats)• Thumping or fluttering in the chest
• Sensation of heart racing• Feeling faint or tired• Light‐headedness or passing out• Shortness of breath• Chest pain or discomfort
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Treatment
• Treatment varies depending seriousness of the condition
• Medication
• Internal implanted cardiac defibrillator (ICD)
• Cardiac Pacemakers
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Cardiac Pacemaker
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Interesting facts
• In 2002 about 3 million people worldwide with a pacemaker
• Each year about 150 000 pacemakers implanted
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When do you need a pacemaker?
• Most common reasons are bradycardia
and heart block
• Aging or damage to your sinus nodes
• Medical procedure to treat an arrythmia called atrial
fibirllation
• Taking heart medicine which may slow heart beat
• Problem with heart muscles
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What is an artificial pacemaker
• A device placed in the chest or abdomen to help control the heart to beat at a normal rate
• To treat arrhythmias
• Use low‐energy electrical pulses to overcome faulty electrical signaling
• Monitor and record heart’s electrical activity and heart rhythm
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How it works
• A pacemaker consists
of a battery, a computerized
generator, and wires
with
sensor.
• Electrode detects heart’s electrical activity• Computer directs generator to send impulse
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History of the Cardiac Pacemaker
• Hyman’s Pacemaker
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History of Cardiac Pacemaker
• The first implantable pacemaker
• In 1959 by Wilson Greatbatch
and W.M. Chardack
• 6cm in diameter and 1.5cm thick
• Total weight was 180g• A pulse forming oscillator and an amplifier
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History
• Demand pacemaker
• Adding a sensing amplifier to fixed‐rate pacemaker
• Long battery life• Introduced by Berkovits
in 1964
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History of Cardiac Pacemaker
• Dual‐Chamber Pacemaker
• 2 pacing leads• Mimic the heart’s natural way of pumping
• Ventricular electrode, Neutral electrode, Artrial
electrode.
• FET is inserted at feedback path of the ventricular electrode.
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History
• Rate‐Response Pacemaker
• Early 1980s• Regulate the pacing rate base on the output
of a sensor system
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Types of Pacemakers
• Three different systems exist‐single chamber ‐dual‐chamber
These systems can have different pacings‐demand‐fixed rate‐rate responsive
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Pacemaker Code Used to Describe Various Pacing Modes
1st
position 2nd
position 3rd
position 4th
position 5th
position
Chamber
Paced
Chamber
Sensed
Response to
Sensing
Rate
Modulation
Multisite
Pacing
A A T O O
V V I R A
D D D V
O O D
A, atrium; V, ventricle; D, dual (both chambers); O, none; T, triggered; I, inhibited; R,
rate adaptive
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Case Study
• Insights into Pacemaker Lead‐Induced Venous Occlusion
• Side effects of pacemakers is still relatively unknown
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Patients
• For the study they used 3 patients
• For each patient they constructed computer based veins of veins with and without pacemaker leads
• Calculated velocity shear stress pressure fields mean time exposure and compared veins with and without leads
Patient Age Sex Body Surface Area Pacing Indication
1 58 F 1.58 Complete heart block
2 85 F 1.61 Trifascicular
block
3 75 M 1.87 Atrial
fibrillation
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Computer constructed Veins
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Velocity
Patient 1 velocity increased with the leads except in the areas between the leads
and the vessel wallPatient 2 saw the same effectPatient 3 saw less of a change because the patients leads were further spaced out
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Shear Stress
Shear stress increased by 25% in all patients between the leads and the vessels body
Pressure Field
The pressure field difference was minimal between veins with leads and without
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Mean Time Exposure
The MET in both cases was greater near the vessel walls than in the middle
of the vein. When the leads were implanted the MET increased in the area between
the vessel wall and the lead
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Results
• Helped to improve predicting areas in danger of blood clotting• From the study they also saw that positioning of leads in locations
where the velocity is relatively high in the no‐lead condition results
in relatively high flow rate and low stasis near the leads
• The opposite is seen for low flow rate • A novel application of computational blood flow simulation
techniques
In the Area between leads and the vessel wall
Low Velocity
Mean Time Exposure Increase
Low shear stress regions
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How a pacemaker is implanted
• Insertion of intravenous line into a vein
• Numb the area where the pacemaker will be put
• Place a needle in large vein, thread the wire into the vein
• Make a small cut into the skin of chest/abdomen
• slip the pacemaker through the cut
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Surgery
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Risks of Surgery
• Swelling, bleeding or infection• Blood vessel or never damage
• A collapsed lung• A bad reaction to the medicine
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Check Ups
• Pacemaker should be evaluated by a cardiologist every 3‐6 months
• Check the effectiveness of the pacemaker
• The battery life
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• The Future of Pacemaker
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Future
• A pacemaker that uses the body to
power itself
• No more battery
• More space
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Future
• Wireless pacemakers• Have been seen to help
patience with sleep apnea• Elderly people falling can
sometimes be caused do to abnormal heartbeat
• Getting the pacemaker to be compatible with an MRI
machine• Vulnerable to radio attack
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Things To Note
Heart may seem basic
at first but it takes many
parts to work in unison for
it to function properly
As a result many
complications that can arise
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Thanks for listening
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Bibliography• http://www.emedicinehealth.com/heart_rhythm_disorders/page6_em.htm#Heart%20Rhyth
m%20Disorders%20Treatment
• http://www.abcarticledirectory.com/Article/Do‐You‐Need‐a‐Pacemaker‐‐Here‐are‐the‐Main‐
Symptoms/186515
• http://www.nhlbi.nih.gov/health/dci/Diseases/pace/pace_whatis.html• http://www.hrspatients.org/patients/treatments/pacemakers.asp• http://www.uptodate.com/patients/content/topic.do?topicKey=~xxx2NnT7Fmuqt• http://www.reuters.com/article/idUSTRE4A94I220081110• http://circ.ahajournals.org/cgi/content/full/105/18/2136• http://www.engadget.com/2009/08/11/worlds‐first‐wireless‐pacemaker‐talks‐to‐your‐
doctor‐daily‐w/
• http://emedicine.medscape.com/article/780825‐overview• http://www.springerlink.com.libaccess.lib.mcmaster.ca/content/y927g07j42486534/fulltext.
html
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• http://inventors.about.com/library/inventors/blcardiac.htm