Cardiac Pacemakers
Aishwarya Sreenath Naheed Baksh Presentation Outline
z History of pacemaker z Anatomy of the heart z Natural pacemaker z Hemodynamics of heart z Types of artificial pacing z Basics structure, materials and power supply z Types of permanent pacemaker z When are pacemaker prescribed z Hemodynamic effects of cardiac pacemakers z Example: Stokes Adams Syndrome z Implementation and implementation risks z Future
2 History of Artificial Pacemakers
z 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.
z Re-animation chair, “FRANKENSTEIN”
z 1932 American physiologist Albert Hyman invented an electro-mechanical instrument, and he named it “artificial pacemaker”
3 First human pacemaker, Made In Canada
z 1950, Canadian Electrical Engineer John Hopps and surgeon Wilfred Gordon Bigelow designed the first pacemaker to be used on patients in Toronto General Hospital.
z John Hopps was the founding president of the Canadian Medical and Biological Engineering Society
z A Transcutaneous pacemaker
z Painful for the patient
z Used the AC wall sockets there was a potential risk of electrocution.
4 PM – 65
z Early 1950, Paul Zoll z Both electrocardiograph and electrical pulse generator. z Pace the heart from external device. z Also Transcutaneous z Uncomfortable z Limitations in movement z Acceptable as long as the pacemaker was considered emergency apparatus for post- surgical care 5 First implantable pacemaker
z Dr. C. Walton Lillehei encountered a power failure and thus realized that a pacemaker should be a compact device that runs on batteries.
z Earl Bakken upon Dr. Lillehei’s request, designed a prototype that ran on batteries.
z Engineer Rune Elmqvist and Dr. Ake Senning created the first implantable pacemaker and successfully implanted in a patient on October of 1958.
z After that all the developments are based on the implantable pacemaker model.
6 Further Developments
z 1975 - Lithium-iodine batteries took battery life from months to years z mid-1970s, pacemaker settings could be programmed using radio-frequency signals. z 1980’s rate responsive pacing z 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.
7 Basic heart Structure
8 Blood flow
9 Conduction System
z Autorhythmic fibers are specialized cardiac muscle cells that cause an inherent and rhythmical electrical activity in the heart z Autorhythmic fibers are self excitable- they simulate contraction without a requisite electrical impulse from the central nervous system z A single cardiac muscle cell can contact rhythmically at a steady rate without any input z If two cardiac muscle cells are in contact, the one that contracts first will simulate the other to contract z The contractile activity is regulated by the autonomic nervous system z Cardiac muscle cells are connected to each other through intercalated discs which support synchronized contraction of the cardiac tissue
10 Intercalated discs
Intercalated discs conduct electrochemical potentials between the cytoplasms of adjacent cells through gap junctions 11 Cardiac Action Potential Propagation
12 Pathway of AP
13 Hemodynamics of heart
z EDV (END DIASTOLIC VOLUME) z ESV (END SYSTOLIC VOLUME) z Stroke Volume, SV = EDV – ESV z Generally SV = 70 ml/beat z HR = heart rate = 75 beats/min z CO = HR x SV z CO = 5250 ml/min (5.25 L/min)
14 Types of artificial pacing
z Percussive Pacing z Transcutaneous Pacing z Transvenous Pacing z Permanent pacing
15 Percussive Pacing
z Strike from a distance of 20-30 cm with closed fist on the left lower edge of sternum.
z The pressure in the ventricle should rise 10- 15 mm hg.
16 Transcutaneous pacing
z External method z Emergency option z Two pads are placed on the patient z Starting with low current the pacemaker is set to the optimal current z Not a comfortable procedure
17 Transvenous Pacing
z Bridge to permanent pacemaker placement z A sterilized wire is placed in a vein and carried to an atrium or ventricle. z The wire is attached to an external pacemaker
18 Permanent Pacing
z Implanted device similar to transvenous pacemaker z Powered by battery that runs for 6-12 years. z 2 components 1) Pulse generator 2) Insulated lead(s) and electrodes.
19 What is an artificial pacemaker?
z A pacemaker is an electronic device implanted in the body to regulate the heart beat. z A Pacemaker is not designed to defibrillate the heart by delivery of shocks. z The PM delivers electrical stimuli over leads with electrodes in contact with the heart.
20 Basic structure of pacemaker
z Pulse generator can be both rate responsive or fixed rate z Pacing leads are passed through a vein (in this case SVC) z Then the electrodes are placed on the myocardium of the desirable location z Figure: Atrioventricular pacemaker
21 Materials used in Pacemaker
z Qualities for the materials used in the pacemaker: – Lowest stimulation voltage – Possible long term implementation – Biocompatibility and nontoxicity z Stainless steel electrodes are replaced by cobalt alloys, platinum-iridium alloys. z Carbon is also being used to some extent. z Stainless steel is still the most cost efficient z Pulse generator is housed in a titanium container
22 Power supply
z Mercury-zinc battery – 48-60 months z Lithium Iodide battery – 10+ years z Biothermal Batteries (Under progress)
23 Types of permanent pacemakers
z Single-Chamber Pacemakers z Dual-Chamber Pacemakers
24 Single Chambered Pacemaker
z One wire is placed on the heart chamber z Either Atrium or the Ventricle z Figure: Single chamber ventricular pacemaker z Generally fixed rate z $2,500.00 cheaper from dual chambered but similar efficiency in many cases.
25 Dual Chamber Pacemaker
z Two leads are placed in two different chambers of heart z Generally one lead goes to a ventricle and the other goes into the atrium z This approach more closely matches the natural pacing of the heart z 40% of the pacemakers used in Canada are dual chamber.
26 Types of pacemaker
z Fixed rate pacemakers – 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. z Rate responsive pacemaker – Determines what the heart rate should be from moment to moment
27 Rate Responsive Pacemaker
z Technological advancements
z The more the patient’s body is moving the faster the heart rate should be.
z 2 major mode to detect the optimal cardiac output – Activity sensor – Breathing sensor
28 When are pacemakers prescribed?
z Bradycardia z Fibrilation z Heart failure z Syncope
29 Quiz
z What is Cardiac Output?
30 Hemodynamic effects and issues
z Cardiac output decreases with many heart problems.
z CO = HR x SV
z The low CO is augmented when HR is increased by using the artificial pacemaker.
z CO increases with the increment of rate until a maximum level of CO is reached.
z Optimal rate = maximum cardiac output
z This maximum level is very close to the CO in people with no heart trouble. 31 Frank-Starling Law Of The Heart
z The greater the heart muscle is stretched during the filling, the greater the quantity of blood pumped.
32 Hemodynamic effects and issues
z When CO is maximum, increase in heart rate decreases the stroke volume.
z Thus, if artificial pacemaker is applied to a normal heart, no significant change in cardiac output will be observed.
33 Stokes Adams Syndrome example
z Heart temporarily loses connection between atria and ventricles. z Temporary heart block causing bradycardia. z Brain does not get enough oxygen rich blood. z Syncope (faint) and seizure
34 Causes
z Heart diseases that affect the AV node. z Surgical trauma – Repair of a heart defect – Replacement of valves z Cardiomyopathies z Myocarditis z Medication
35 Diagnosis
z Electrocardiogram
z Echocardiogram
z Biopsy
z Electrophysiological study
36 Treatment
z Depending on the cause. z Discontinuation of medication z Pacemakers are used in severe cases. z AV block z One electrode is placed on the atrium and the other on the ventricle.
37 Implementation
z Pacemaker surgery is done under local anesthesia. z A small incision is made where the pacemaker will be located. z The leads are guided through a large vein to the heart. z The pulse generator is then placed under the skin and then the incision is closed. z Approximately 1 hour long z Regular monitoring of BP and HR might be needed. z The incision spot should not be wet for 10 days. z Minor pain and discomfort might occur for 5 – 10 days.
38 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
39 Future of Cardiac Pacemakers
z Biothermal Batteries – Converts body’s own heat into electricity
z Transtelephonic monitoring – Already exists – Improving to a cellphone-like device
z In body communication system – 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.
40 Any Question?
Thank you for your attention References
z Harold Siddong and Edgar Sowton, “Cardiac pacemakers”, Charles C Thomas Publisher z L.A. Geddes, “Cardiovascular Devices and Their Applications”, Ed. 10, Wiley-Interscience Publication z Dr. Richard Sutton and Dr. Ivan Bourgeois “The foundation of Cardiac Pacing, Pt.1”, Futura Publishing Company. Vol 1, 1991 z Heinemann, William, Fontaine. G, Grosgogeat.Y, and Welti. J.V.T. “The Essentials of cardiac pacing”. France: Cedig Publisher, 1976. z 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. z Gerrard J. Tortora, Derrickson, Bryan. “Principles of Anatomy and Physiology”. United States of America: John Wiley & Sons, Inc, 2006. z http://www.howstuffworks.com/heart.htm z http://www.nlm.nih.gov/medlineplus/tutorials/pacemakers/htm/index.htm z http://heartdisease.about.com/cs/arrhythmias/a/pacemakers.htm z http://www.uvka.de/univerlag/volltexte/2005/77/pdf/Oertel_Modelling_the_human_cardiac_fluid.pdf z http://www.emedicine.com/emerg/topic699.htm z http://www.emedicine.com/med/topic189.htm z http://www.medicinenet.com/pacemaker/article.htm z http://www.thebakken.org/artifacts/pacemakers.htm z http://www.sdrs.org/equipment-als.htm z http://www.cardiocare.co.za/courses.php 42 References (Cont’d)
z http://www.chw.org/display/displayFile.asp?filename=/Groups/Pediatri cHealthInformation/CardiovascularDisorders/pacemk10.jpg z http://fhs.mcmaster.ca/main/news/news_archives/pace.htm z http://heart.health.ivillage.com/arrhythmia/stokes-adams.cfm z http://www.londonafcentre.co.uk/images/pacemaker.gif z http://www.chw.org/display/displayFile.asp?filename=/Groups/Pe diatricHealthInformation/CardiovascularDisorders/pacemk9.jpg z http://www.cardioassoc.com/patient_pgs/procedures/pacemaker.asp z http://en.wikipedia.org/wiki/Artificial_pacemaker z http://www.medicineonline.com/reference/Computers/info/Pacemaker. htm z http://en.wikipedia.org/wiki/Cardiac_pacemaker z http://en.wikipedia.org/wiki/Cardiac_muscle
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